Y2 2013 Spring Microbiology Block II – Flashcards

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question
What is the primary causative agent of tooth decay?
answer
Streptococcus mutans
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What causes cariogenic dental plaques?
answer
Mouth acidity
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What is periodontal disease?
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Inflammation of the gums in response to plaque bacteria such as in dental calculus or gingivitis
Responsible for tooth loss in the elderly
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What causes gingivitis?
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Porphyromonas gingivalis
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What causes trench mouth?
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Synergistic infection of spirochetes (oral spirochete of Treponema genus; T. pallidum is the cause of syphilis) and anaerobic bacteria
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What causes watery diarrhea?
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Pathogenic mechanisms that attack the proximal small intestine (more than 90% of physiologic net fluid absorption occurs)
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What organisms cause the purest form of watery diarrhea?
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Enterotoxin-secreting bacteria such as Vibrio cholerae and enterotoxigenic Escherichia coli (ETEC), which cause fluid loss without cellular injury
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Which causes of watery diarrhea are uniquely not self limiting to 1-3 days?
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V. cholerae, which usually produces a more severe illness

Giardia lamblia, which produces a watery diarrhea that may last for weeks
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What is dysentery?
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Rapid onset of frequent intestinal evacuations, but the stools are of smaller volume than in watery diarrhea and contain blood and pus
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What causes dysentery?
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Inflammatory and/or destructive changes in the colonic mucosa either by direct invasion or by production of cytotoxins
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What causes enteric fever?
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Penetration by the organism of the cells of the distal small bowel with subsequent spread outside the bowel to the biliary tract, liver, mesentery, or reticuloendothelial organs
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What is the only infection causing enteric fever that is well studied?
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Typhoid fever caused by Salmonella enterica serotype Typhi
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What are the most common causes of traveler's diarrhea?
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50% caused by ETEC
10%-20% by Shigella species
Ingestion of uncooked or incompletely cooked foods is the most likely source of infection
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What are the most common causes of food poisoning?
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Salmonella, Clostridium perfringens, and S. aureus
Most often due to improper storage temperature
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What are the most common causes of hospital associated diarrhea?
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E. coli (in infants)
C. difficile (patients on antibiotics)
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Which hepatitis virus is "silent" and often goes undetected?
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Hep C
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How is liver cell damage present?
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Hepatic cell degeneration and necrosis, cell dropout, ballooning of cells, acidophilic degeneration of hepatocytes forming Councilman or apoptotic bodies
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What are the unique features of Hep A?
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Single stranded RNA picornavirus
Resists inactivation and is stale at -20C with low pH
Never becomes chronic, has only one serotype, no animal reserve, vaccine existence is leading to eradication of the virus
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What kind of abnormal liver cells are characteristic of liver disease?
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Kupffer cells
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What are the symptoms of Hep A?
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Fever, anorexia, nausea, pain in upper right abd, jaundice, dark urine and clay-colored stool, enlarged, tender liver, elevated serum aminotransferase and bilirubin
Will never cause cancer or progress to chronic liver disease
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How is Hep A treated?
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Almost all are self limiting to a few weeks-months
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How is Hep A detected in serology studies?
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Fecal HAV detected 4-6 weks
IgM Anti-HAV detected early on but then drops
IgG is inclusive because it increases over time, needs to see the trend
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How long in advance must immune serum globulin be given to confer temporary immunity to Hep A?
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Protective if given before or during the incubation period of the disease
Not indicated once symptoms have appeared
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What are the unique features of Hep B?
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Member of hepadnaviridae family
Smallest DNA virus known
All newborns become chronic, 50% of children become chronic
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What is present in the nuclei of cells infected with Hep B?
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HBcAg, HBeAg, and hepatitis B DNA
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What is present in the cytoplasm of cells infected with Hep B?
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HBsAg
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The HBV S gene codes for what?
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The "major" envelope protein HBsAg
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What does the HBV P gene code for?
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Largest gene, codes for DNA polymerase
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What does the HBV C gene code for?
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Two nucleocapsid proteins, HBeAg, a soluble, secreted protein and HBcAg, the intracellular core protein
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What does the HBV X gene code for?
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HBxAg, which can transactivate the transcription of cellular and viral genes; its clinical relevance is not known, but it may contribute to carcinogenesis by binding to p53
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How do infants acquire HBV from their mother?
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Not vertically, accquired intrauterally via ingestions or abrasions during birth
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What are the consequences of chronic HBV infection?
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Necrosis of hepatocytes,
Collapse of the reticular framework of liver
Progressive fibrosis
Leads to syndrome of postnecrotic hepatic cirrhosis
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What causes extrahepatic manifestations of HBV?
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Deposition of HBsAg-anti-HBs circulating immune complexes in tissue blood vessel walls results in prodromal serum sickness-like syndrome, glomerulonephritis, and nephritic syndrome
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Polyarteritis nodosa is associated with which Hep virus?
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HBV
Develops in considerably fewer than 1% of patients with chronic HBV infection
However, 20 to 30% of patients with PAN have HBsAg in serum
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Essential mixed cryoglobulinemia is associated with which Hep virus? What are its features?
answer
HBV, HCV
Precipitates at cold temp
Arthritis
Cutaneous vasculitis (palpable purpura)
Glomerulonephritis (occasional)
Circulating cryoprecipitable immune complexes (more than one immunoglobulin class)
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What are the characteristics of HBsAg?
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HBV surface antigen formed in excess and seen in serum
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What are the characteristics of HBcAg
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HBV core antigen found in nucleus of infected hepatocytes by immunofluorescence
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What are the characteristics of HBeAg
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HBV glycoprotein associated with the core antigen, used as a marker of potential virus activity, only seen when HBsAg is also present
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What are the characteristics of Anti-HBs
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Ab to HBsAg, correlates with past infection or immunization
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What are the characteristics of Anti-HBc
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Ab to HBcAg, seen in acute infection and chronic carriers, can be either IgM or IgG (acute vs. chronic)
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Anti-HBc IgM indicates what?
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Acute HBV infection
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Anti-HBc IgG indicates what?
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Chronic HBV infection
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Presence of Anti-HBe indicates what?
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Virus is not actively reacting and is in recession
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What is the best diagnostic measure for HBV detection?
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IgM antibody to HBcAg along with or without HBsAg in the serum
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How is vertical transmission of HBV to newborns prevented?
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Use of combined HBIG and HBV vaccine
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How do you treat chronic HBV?
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Interferon-alpha, Lamivudin, Adefovir
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What is the leading cause for liver transplants in the US?
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Liver failure due to Hep C
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How is HCV contracted?
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Commonly transmitted through blood contact (blood transfusion or needle sharing) than through transfer of body fluids; vertical transmission is possible
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What is the most common complication of HCV?
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Chronic liver disease (80% of cases with a course of intermittent inflammation and normality)
10-20% of chronic patients develop cirrhosis or cancer in the long run
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What is the average time from infection to the development of chronic hepatitis in HCV patients?
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10-18 years
Often asymptomatic
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What are the extra-hepatic manifestations of HCV?
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Essential mixed cryoglobulinemia (EMC)
Circulating immune complexes containing HCV RNA
Immune-complex glomerulonephritis
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How is HCV diagnosed?
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Detection of HCV antibody
May remain negative for 1-3 weeks after clinical onset
May never become positive in up to 20% of patients with acute, resolving disease
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How is HCV treated?
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Combination treatment with interferon-a and ribavirin
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The protein-RNA complex of Hep D is surrounded by what?
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HBsAg
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How is Hep D diagnosed?
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IgM or IgG antibodies or both to the delta antigen in serum
IgM antibodies appear within 3 weeks of infection and persist for several weeks
IgG antibodies persist for years
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How is Hep D prevented?
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By preventing Hep B
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How is Hep D treated?
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Interferon alpha
Response to treatment in patients with delta hepatitis (and hepatitis B) is less than in those with hepatitis B alone
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The majority of GI pathogenic bacteria grow on what medias?
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Majority are gram-neg and grow on MacConkey agar which inhibits gram-pos growth
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How is Hektoen agar used to diagnostically distinguish GI pathogenic bacteria?
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Inhibits common colon flora
Selective to recover Salmonella and Shigella spp.
Indicators to detect H2S production (black centers to colony)
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What does Campylobacter spp. grow on?
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Enriched blood agar
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What is acute diarrhea and what are its causes?
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Diarrhea lasting 7-14 days caused by:
Drugs
Infectious Agents (Virus, Bacteria, Parasite)
Feeding after a long fasting
Fecal Impaction
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Which GI bacteria have vaccines?
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Most don't
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What makes distinguishing E. coli so difficult?
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Many strains are a part of the normal GI flora and basic diagnostics will not discriminate between normal and pathogenic E. coli
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What are the most common causes of Enterotoxigenic E. coli (ETEC)?
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Ingestion of contaminated water or food
Major cause of travelers diarrhea
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What is the most common progression of a GI infection?
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Bacteria pass through to intestines
Attachment to mucous layer or intestinal epithelia
Secretion of toxins
Induction of diarrhea and potentially other symptoms
Clearance by host immune system
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What are the symptoms of an Enterotoxigenic E. coli (ETEC) infection?
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Watery diarrhea, cramps, vomiting, malaise, fever
More severe symptoms if the infecting ETEC strain secretes both types of toxins
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What toxins are secreted by Enterotoxigenic E. coli (ETEC)?
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Either one or both:
ST (small toxin)
LT (heat labile toxin pierces the membrane of target cell)
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How is Enterotoxigenic E. coli (ETEC) diagnosed?
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Characteristic symptoms with ONLY lactose fermenting organisms on differential media
ELISA for toxins
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How is Enteropathogenic E. coli (EPEC) contracted?
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Lack of good hygienic practices: fecal oral contamination
Most often in infants (1 year old or less usually) with adults as carriers
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How is the progression of Enteropathogenic E. coli (EPEC) unique?
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Secretes of factors that alter the “host” cells (Type III secretion)
Changes epithelial cell cytoskeleton to create a “pedestal” for the bacterial cell
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What are the symptoms of an Enteropathogenic E. coli (EPEC) infection?
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Fever, vomiting, watery diarrhea that may contain large amounts of mucus
Associated with clusters in the US such as daycare, hospitals, nursery
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How is Enterohemorrhagic E. coli (EHEC) most often contracted?
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Lack of good hygienic practices
Ingestion of insufficiently cleaned or cooked foods
Reservoir is usually adult cattle which are asymptomatic
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How is the progression of Enterohemorrhagic E. coli (EHEC) unique?
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Also involved in Type III secretion and pedestal formation
May result in temporary or permanent systemic damage
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What are the signs and symptoms of Enterohemorrhagic E. coli (EHEC)?
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Watery diarrhea that progresses to *bloody diarrhea, abdominal cramps, +/- fever, may also develop hemolytic uremic syndrome (HUS)
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What causes hemolytic uremic syndrome (HUS)?
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o Toxin release into the bloodstream leads to lysis of erythrocytes, thrombocytes, and destruction of glomerular capillary endothelial cells
Children and elderly are more susceptible, can be fatal
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Hemolytic uremic syndrome (HUS) is most commonly associated with what?
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O157:H7
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What toxins are secreted by Enterohemorrhagic E. coli (EHEC)?
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Functionally and structurally related to the Shiga toxin
AB type toxins
The A subunit interacts with cellular ribosomes cleaving a single adenine residue from the 28S rRNA* leading to a shut-down of host protein synthesis
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What special consideration should be made in the treatment of Enterohemorrhagic E. coli (EHEC)?
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Monitoring for renal failure
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How is Enterohemorrhagic E. coli (EHEC) diagnosed?
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Cultures that fail to ferment sorbitol
MacConkey agar using sorbitol instead of lactose
ELISA for toxins

MUG assay: EHEC typically do not produce b-glucoronidase while 92% of other strains do
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How is Enteroinvasive E. coli (EIEC) contracted?
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Fecal to oral contamination
Reservoirs involve human sources
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What is unique about the progression of Enteroinvasive E. coli (EIEC) infections?
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Secretion of factors that induce uptake and transmission by M cells*
Entry into the inferior or lateral sides of intestinal epithelial cells
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What are the signs and symptoms of an Enteroinvasive E. coli (EIEC) infection?
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Many are asymptomatic or with transient fever
Early: Fever, severe cramps, Watery diarrhea
Late: Reduced fever, increased diarrhea with blood*, urgency, tenesmus
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What additional treatment option can be used for Enteroinvasive E. coli (EIEC)?
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Antibiotics may be administered for more severe cases and will decrease the length of symptoms
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How is Enteroinvasive E. coli (EIEC) diagnosed?
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HE (Hektoen enteric) agar, MacConkey
DNA probes are commercially available
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What is unique about the progression of Enteroaggregative E. coli (EAEC) infections?
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Bacteria replicate and aggregate in a unique “stacked brick” fashion (biofilm)
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What is a unique symptom of Enteroaggragative E. coli (EAEC) infection?
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May cause a protracted course of diarrhea (>14 days) in adults and children in all parts of the world
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What are the toxins secreted by Enteroaggragative E. coli (EAEC)?
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ShET1 (Shigella enterotoxin 1) similar to a toxin common in Shigella
EAST1 shows similarity to ETEC toxin ST
Pet: A serine protease that alters the enterocyte cytoskeleton (not in all strains)
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Which E. coli strains cause watery diarrhea?
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EPEC, ETEC, most Viral, (EAEC)
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Which E. coli strains cause bloody diarrhea?
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EHEC, Shigella spp./EIEC, (EAEC)
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Which E. coli strains cause watery and mucoid diarrhea?
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EPEC
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Which E. coli strains are associated with recent travels?
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ETEC, EAEC, Rotavirus
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What is the appearance of Yersinia spp.?
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Gram negative bacillus
motile at 25C but not 37C
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What does Yersinia culture on?
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Most enteric media except Salmonella-Shigella agar
Produces urease
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Yersinia is very sensitive to levels of what mineral?
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Iron
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How is Yersinia contracted?
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Ingestion of contaminated food or water
Handling infected animals or carcasses
Very rarely blood transfusion
Swine is the primary reservoir
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What is unique about the pathogenesis of Yersinia infections?
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Bacteria invade the M cells of the gut and start replicating
Phagocytic cells ingest Yersinia spreading them to the reticuloendothelial system, and are then killed by the bacteria delaying the immune response
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What are the signs and symptoms of a Yersinia infection?
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Enterocolitis
Mesenteric adenitis and terminal ileitis
Exudative pharyngitis
Tender red nodules on extensor surfaces of limbs
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What symptoms does enterocolitis refer to?
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Fever lasting 1-3 weeks, diarrhea containing mucous and blood, abdominal cramps, anorexia, nausea and vomiting, Rectal bleeding in severe cases
Potentially severe dehydration
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What post-infectious syndrome is common in patients recovering from a Yersinia infection?
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Reactive arthritis
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What is the general function of toxins secreted by Yersinia?
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Most of the virulence factors are regulated in expression by the local environment and are aimed at suppressing the immune system
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How is Yersinia diagnosed?
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Stool culture on enteric media
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What media is used to culture Francisella tularensis?
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Requires special media for growth that is enriched in cysteine
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How is Francisella tularensis contracted?
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Insect bites (no human to human transmission)
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What are the signs and symptoms of Francisella tularensis?
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Fever (up to 104), chills, headache, myalgias, possible delirium
Inflamed blister that fills with pus and opens to form an ulcer, swollen lymph nodes
Severe sore throat
Chest and abdominal pain, fatigue, weight loss, diarrhea
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How is Francisella tularensis diagnosed?
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Serology is negative the first week but still the best means for confirmation
Diagnosis is usually based on clinical suspicion
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How is Francisella tularensis treated?
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Antibiotics (gentamicin or ciprofloxacin)
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How is Brucella melitensis contracted?
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Direct contact with infected animals or their secretions through skin breaks
Ingestion of unpasteurized dairy products derived from infected animals
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Describe the pathogenesis of Brucella melitensis
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Transport to regional lymph nodes and growth in lymphoid cells
Spread from the lymph nodes to the reticuloendothelial system
Bursts of bacteremia
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What are the signs and symptoms of Brucella melitensis?
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Usually 1 of 3 categories:
Febrile illness that resembles typhoid but is less severe
Fever and acute monarthritis, typically of hip or knee, in a young child
Long-lasting fever, misery, and low-back or hip pain in older men
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How is Brucella melitensis diagnosed?
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Culture from blood, bone marrow, or other tissues
Grows very slowly so allow extra time in cases of suspicion
Serum agglutination test may also be used
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Describe the appearance of Brucella melitensis
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Small gram-negative rod
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Describe the appearance of Bacteroides fragilis
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Gram-negative rod
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What media is used to culture Bacteroides fragilis?
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Forms colonies overnight on blood agar
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What are the virulence factors and toxins of Bacteroides fragilis?
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Capsule resists phagocytosis and can independently lead to abscess formation
Secretes a heparinase that promotes clotting
Some strains secrete a 20 kDa metalloprotease toxin (BFT) that causes disease without the need for epithelial breaks
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How is Bacteroides fragilis contracted?
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Can be part of the normal flora and these strains require a break in the anatomic mucosal barriers (unless metalloprotease toxin is present)
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How is Bacteroides fragilis treated?
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If causing acute diarrhea due to ingestion, is self limiting
If due to epithelial break: Abscess drainage and antibiotics
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What is the physical appearance of Helicobacter pylori?
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Gram negative curved rod with multiple sheathed flagella for motility
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How is H. pylori cultured?
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Grows on Skirrow media
Requires a microaerophilic atmosphere and is slow (3-5 days) to grow
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How is H. pylori transmitted?
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Person to person by fecal-oral route
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What is the most common cause of gastritis, gastric ulcer, and duodenal ulcer?
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H. pylori
Considered a class I carcinogen
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What mediates the virulence factor of H. pylori?
answer
VacA is toxic and directly influences inflammation
CagA stimulates cytokine IL-8 and neutrophil-activating protein (NAP)
Net effect is gastritis, thinning of gastric mucosa, ulcers
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How are T and B lymphocytes involved in the creation of gastric ulcers?
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H. pylori infection causes lymphocyte infiltration which causes epithelial tissue damage rather than removal of the pathogen
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What is the purpose of urease secreted by H. pylori?
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Converts urea to ammonia which tends to neutralize the gastric acid
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What are the symptoms of H. pylori induced gastritis?
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Often symptom free
In symptomatic: belching, nausea, anorexia, vomiting, epigastric pain, bleeding
Possible pyloric stenosis
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How is an H. pylori infection diagnosed?
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Endoscopic biopsy and culture
Detection of urease activity via urease breath test with 13C- or 14C-labeled urea
Serology for specific antibody
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How is H. pylori treated?
answer
Combo of antimicrobials and acid reducers
Metronidazole, tetracyclin, clarithromycin*, and amoxycillin*
Proton pump inhibitor
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What is the general pathogenic mechanism of bacterial intestinal diseases?
answer
Attachment by pili or other adhesion
Some bacteria transfer substances into host cell that mediate bacterial attachment
Toxin production
Cell division
Loss of microvilli
question
What is the physical appearance of Vibrio cholera?
answer
Curved gram neg rod commonly found in salt water
Highly motile with single polar flagellum
Cells may be linked end to end forming S shapes and spirals
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How is Vibrio cholera cultured?
answer
Oxidase positive and can grow both in aerobic and anaerobic conditions
Grown on Thiosulfate Citrate Bile Salt Sucrose (TCBS) medium which inhibits gram pos
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What is the major virulence factor for Vibrio cholera?
answer
Cholera toxin
Colonizing factor known as the toxin-coregulated pilus (TCP)
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How is Virbrio cholera detected by serology?
answer
H and O antigens (especially enterobacteriae)
question
What is the mechanism of action of cholera toxin?
answer
Catalyzes the ADP-ribosylation of the GS (stimulatory) regulatory protein, "locking" it in the active state
Causes persistent activation of adenylate cyclase which causes cAMP accumulation for active secretion of Na+, K+, HCO3-, and water out of the cell
question
How does Vibrio cholera cause fluid loss?
answer
Increased adenylate cyclase via cholera toxin
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What is the osmotic make up of diarrheal fluid?
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Can amount to many liters per day, with approximately the same sodium content as plasma but two to five times the potassium and bicarbonate concentrations
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What regulates the virulence factors of Vibrio cholera?
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Transmembrane protein (ToxR ) that "senses" environmental changes in pH, osmolarity, and temperature which convert it to an active form
question
What are the symptoms of cholera?
answer
Rapid onset, abd pain, rushes of peristalsis, loose, watery stool containing mucus flecks- the “rice-water stool”
Muscle cramp due to electrolyte imbalance
In severe, hypotension, shock and death may occur within hours if untreated
question
How is cholera diagnosed?
answer
Isolation of the organism from stool by culture on common bacteriological medium (e.g. blood agar and MacConkey agar) or on a selective medium (thiosulfate-citrate-bile salt-sucrose agar)
Latex agglutination test
question
How is cholera treated?
answer
Immediate fluid replacement
Antimicrobials: tetracycline or TSX and erythromycin
Usually self-limiting
question
Less common vibrio species??
answer
question
Describe the physical appearance of Campylobacter jejuni (dysentery)
answer
Curved motile gram neg rod
Have polar flagella that are often attached to the ends giving an “S” or a “seagull” appearance
question
How is Campylobacter jejuni cultured?
answer
Microaerohilic (requires low oxygen tension), oxidase positive
Slow growing (2-4 days, sometimes as long as one week) in selective medium (Campy-blood agar or Skirrow agar) at higher temperature (42C)
question
What is the leading bacterial diarrheal illness in the US?
answer
Campylobacteriosis
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How is campylobacter usually contracted?
answer
Domestic animals or consumption of contaminated meat (poultry)
Ingestion of non-pesteurized cow and goat milk as well
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How is campylobacter associated with Guillain-Barre syndrome
answer
Antibody elicited by ganglioside-like structures in the C. jejuni LPS core oligosaccharide cross-reacts w/ molecules in the host nerve myelin
These abs are found in the serum of pts w/Guillain-Barre syndrome
Similar to molecular mimicry in rheumatic fever
question
What are the symptoms of a campylobacter infection (dysentery)?
answer
Fever
Lower abd pain (may be severe enough to mimic acute appendicitis)
Dysenteric stool containing blood and pus
Vomiting (often not present)
Is invasive
Usually self-limiting, recovers within 3-5days
question
How is campylobacter diagnosed?
answer
Stool isolation and culture via Campy-blood agar or Skirrow agar
Plates are to be incubated in microaerophilic condition
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How is campylobacter contraction prevented?
answer
Pesteurization of milk and beverages and chlorination of water is helpful in preventing outbreaks
Proper cooking and handling of poultry products
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How is campylobacter treated?
answer
Macrolides (erythromycin is the drug of choice) and fluoroquinolones
Resistant to beta-lactams
question
What are the relevant species of salmonella that causes diarrhea?
answer
S. enterica and S. typhi
question
What is the physical appearance of salmonella?
answer
Gram-negative enterobacteria, motile
question
How is salmonella cultured?
answer
Ferment glucoses with acid and sometimes gas; most of them produce hydrogen sulfide (H2S) not urease
Grows on most common bacteriological media, resistant to chemicals such as bile and dyes
question
Describe the pathogenesis of S. enterica
answer
Attaches to the enterocytes and M cells in the small and large intestine by pili
Initiates a cytoskeletal change with formation of ruffles (extension of plasma membrane)
Passes through the cells to the lamina propria to produce inflammation
question
How does S. enterica avoid phagocytosis?
answer
Inducing macrophage apoptosis
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What are the symptoms of salmonella infection?
answer
Often described as “food poisoning”
Nausea
Vomiting
Abdominal pain
Loose motion
Fever
question
What is the classic contaminated food consumed in the contraction of salmonella poisoning?
answer
Potato salad
question
What causes typhoid fever?
answer
Salmonella typhi
Transmitted by contaminated drinking water, usually associated with travel
Requires a large infecting dose
question
Describe the pathogenesis of Salmonella typhii
answer
Similar to that of S. enterica
Also kills macrophages by inhibiting phagosome fusion with lysosomes
Capsular Vi antigen inhibits PMN phagocytosis
question
How does the virulence of Salmonella typhii differ from other strains of salmonella?
answer
Prolonged survival within the macrophages due to its ability to inhibit oxidative burst
Infected macrophages are carried in the lymphatic circulation to mesenteric nodes, spleen, liver and bone marrow
question
What are the symptoms of typhoid fever?
answer
Involves multiple organs
Incubation 13 days
Fever, headache, faint rash on abd
Diarrhea
Relative bradycardia is characteristic
question
What are the most important complications of typhoid fever?
answer
Intestinal (terminal ileum or proximal colon) perforation* and cholecsystitis* are the most important complications
Chronic bacteremia and effects of endotoxins may lead to myocarditis, encephalopathy, or IVC
question
How is Salmonella poisoning diagnosed?
answer
Hektoen enteric agar medium
Bile salts and the indicator dyes inhibit the Gram-pos
Fails to ferment lactose
H2S forms black colonies
question
How do common GI pathogens present on Hektoen enteric agar cultures?
answer
Fermenters produce yellow-pink colonies (e. g. E. coli)
H2S producers (salmonella) form colonies with black precipitate
Shigella colonies are green or transparent
question
How is salmonella poisoning treated?
answer
Fluid and electrolyte replacement is the primary therapeutic approach
Chemotherapy includes chloramphenicol (bone marrow depression is an important side effect, dangerous), STX, ampicillin, ceftriaxone, and quinolones
question
Describe the physical appearance of Shigella
answer
Gram-negative straight rods, nonmotile and non-spore-forming
question
How is shigella cultured?
answer
Selective Hektoen enteric agar
Does not produce urease or H2S, most do not ferment
question
How is shigella contracted?
answer
Strictly a human disease with no animal reservoirs
Person to person transmission by fecal-oral route
question
How does shigella differ in its pathogenesis from other intestinal bacteria?
answer
Invades the cells of the large intestine rather than the small intestine
question
Describe the pathogenesis of Shigella
answer
Bacteria transcytose through the M cells in large intestine into the underlying phagocytic cells
Infects the adjacent cells directly
The cell by cell extension radially creates focal ulcers in the mucosa
Intense acute inflammation in the lamina propria cause the characteristic dysenteric stool
question
What is the significance of Shigella toxin?
answer
Not in all strain, increases severity
Has a strong association with the hemolytic uremic syndrome characterized by break up of RBCs in the tiny blood vessels of the body resulting in anemia and kidney failure with occasional nervous system injury
question
What are the characteristics of dysentery syndrome?
answer
Cramps
Painful straining to pass stools (tenesmus)
A frequent, small-volume, bloody mucoid discharge
question
Most cases of shigella are due to S. sonnei, which presents with what symptoms?
answer
Fever
Malaise, anorexia
Myalgia (sometimes)
Diarrhea (may become dysenteric)
question
How is shigella diagnosed?
answer
Culture on selective Hektoen enteric agar
Slide agglutination tests using O group specific antisera (A, B, C, D)
question
How is shigella treated?
answer
Usually self limiting
Antimicrobials help shortening the period of illness and excretion of the organisms
Antispasmodics are contraindicated
question
What are the characteristics of Picornaviruses?
answer
Poliovirus (3 serotypes)
Hepatitis A Virus
Coxsackievirus groups A and B
question
Describe the pathogenesis of picornaviruses
answer
Initial infection is of intestinal epithelia or pharynx, persists throughout disease
Spreads to submucosal lymphoid tissues (Peyer’s patches or tonsils) and regional lymph nodes
Spreads to and replicates in organs of the reticuloendothelial system
question
What diseases processes/complications are seen with Group A Coxsackievirus infections?
answer
Asceptic Meningitis, Encephalitis, muscle weakness and paralysis (Poliomyelitis-like disease), cerebellar ataxia, exanthems and enanthems
question
What disease processes/complications are seen with Group B Coxsackievirus infections?
answer
Asceptic Meningitis, Encephalitis, Pericarditis, Myocarditis, Epidemic Mylagia, Orchitis
question
What disease processes/complications are seen with Echovirus and Enterovirus infections?
answer
Asceptic Meningitis, Encephalitis, muscle weakness and paralysis (Poliomyelitis-like disease), Exanthems and enanthems
question
What are the disease states of poliovirus?
answer
Abortive poliomyelitis, asceptic meningitis, paralytic poliomyelitis
question
How are picornavirus infections prevented?
answer
Both Inactivated virus (IPV) and Live-attenuated virus (OV) vaccines exist for poliovirus
IPV is now the standard for use in the US
question
How are picornaviruses treated?
answer
Most picornavirus infections are mild and resolve on their own
Injection of Ig to the infecting virus is used in severe cases of neonates or those with Ig deficiency
Supportive care for cardiac or CNS
question
How are picornaviruses contracted?
answer
Fecal-oral route
question
Describe the pathogenesis of rotaviruses
answer
24-48 hour incubation period
Initial infection is of the mature villis tip cells of the small intestine
Tip cell death leads to cell replacement by cells that cannot absorb nutrients as efficiently leading to osmotic diarrhea
question
What is the leading cause of severe dehydrating diarrhea in those under 3 years?
answer
Rotavirus
question
What are the general symptoms of rotavirus?
answer
Vomiting (typically the first symptom)
Abdominal cramps
Watery diarrhea
May frequently occur along with a respiratory tract infection
Lasts 2-8 days, a form of traveler's diarrhea
question
How is rotavirus immunity mediated?
answer
VP4 and VP7 (outer shell) are targets for neutralizing antibodies and humoral immunity plays a large role in viral clearance
question
How is rotavirus infection prevented?
answer
A live-attenuated vaccine is available. The 3 shot course must be completed by 32 months of age due to concerns over a potentially fatal complication
question
How is rotavirus diagnosed?
answer
Shed in large amounts in the stool (only during an active infection), and a variety of molecular and enzymatic tests can confirm infection
question
How is rotavirus treated?
answer
Usually self limiting, can be treated with oral fluids
question
How are Norwalk agent and Noroviruses contracted?
answer
Fecal-oral route, associated with
Foodborne outbreaks associated with unsanitary restaurant workers
Waterborne outbreaks of viral gastroenteritis
Uncooked shellfish
question
How do Norwalk agent and Norovirus infections progress?
answer
Intestinal villi and microvilli become blunted and shortened
Malabsorption of carbohydrates and fats leads to osmotic diarrhea without involvement of adenylate cyclase
Gastric motor function is delayed and may be the cause of nausea symptoms
Lasts 12 to 60 hours
question
What are the symptoms of a Norwalk agent or Norovirus infection?
answer
Nausea, vomiting, cramps, and watery diarrhea
Vomiting is more common in children, and diarrhea in adults
Headache, fever, chills, and myalgias
question
How is immunity to Norwalk agents and Norovirus mediated?
answer
Short term immunity to infection by the same strain (2-3 months)
Lasting immunity is not achieved to any strain
question
How are Norwalk agent and Norovirus infections treated?
answer
Treatment is usually not necessary as the disease is of short term, self-limiting, and is not severe
question
What symptoms appear in Picornavirus infections but no in Norovirus infections?
answer
Rashes, lesions, photophobia, tachycardia
question
Calicivirus infections are more common among what demographic?
answer
Older children and adults and have nausea as a primary symptom
question
What are the Helminths?
answer
Nematodes (roundworms)
Cestodes (tapeworms)
Trematodes (flukes)
question
How does the reproduction of helminths correlate with disease severity?
answer
Adult worms do not multiply in human hosts
Symptoms are usually linked with “worm burden” (number of adults present)
question
What are the nematodes?
answer
Trichuris trichiura (Whipworm)
Enterobius vermicularis (Pinworm)
Ascaris lumbricoides (Roundworm)
Necator americanus and Ancylostoma duodenale (Hookworm)
Strongyloides stercoralis (Threadworm)
question
How is Trichuris trichiura (Whipworm) contracted?
answer
Ingestion of fecal contaminated soil or foods
question
What are the symptoms of Trichuris trichiura (Whipworm)?
answer
Light infections are asymptomatic
Heavy infections can have
Epigastric pain, vomiting, distention, flatulence, anorexia and weight loss may occur, severe cases have Trichuris dysentary syndrome, blood and mucous in stools
question
How is Trichuris trichiura (Whipworm) diagnosed?
answer
Eggs in stool
question
What kind of complications are seen with Trichuris trichiura (Whipworm)?
answer
Parasites typically induce an IgE response and hypereosinophilia
Mast cell activation may lead to the increase in allergic responses and symptoms coincide with GI complaints
Prolapse of rectum
question
How is Enterobius vermicularis (Pinworm) contracted/spread?
answer
Fecal-oral route of infection
Person to person transmission is high, especially in children and institutionalized individuals
Female lays eggs in perianal region causes intense itching, leading to scratching, leading to hand and nail contamination, etc.
question
How do Enterobius vermicularis (Pinworm) infections progress?
answer
Self-infection occurs by scratching perianal area without hand washing
Larvae hatch in the small intestine after ingestion of infective eggs
Adults grow in the colon
Pregnant females migrate nocturnally outside the anus and oviposit while crawling on the skin of the perianal area
question
What are the symptoms of Enterobius vermicularis (Pinworm)?
answer
Intense nocturnal perianal itching
Insomnia
Can migrate to urogenital tract in females causing a vaginitis and lead to secondary bacterial UTI
Scratching may lead to secondary bacterial skin infections
question
How is Enterobius vermicularis (Pinworm) diagnosed?
answer
Tape test from perianal region reveals eggs
question
How is Ascaris lumbricoides (Roundworm) contracted?
answer
Fecal-oral contamination
question
How does a Ascaris lumbricoides (Roundworm) infection progress?
answer
Adult worms live in the lumen of the small intestine, passes eggs in small intestines
Larva penetrates the intestinal mucosa, carried via the portal vein, then systemic circulation to the lungs
The larvae mature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree to the throat, and are swallowed
Egg ingestion to new egg passage takes approximately 9 weeks
question
What are the symptoms of Ascaris lumbricoides (Roundworm) infection?
answer
Usually asymptomatic
Fever, jaundice, chachexia and mental retardation due to malnutrition, pulmonary symptoms, abdominal tenderness due to obstruction or bowel perforation, Loeffler's syndrome, Larva migrans
question
What is Loeffler's Syndrome?
answer
Originally reported as a benign, acute eosinophilic pneumonia of unknown cause characterized by migrating pulmonary infiltrates and minimal clinical manifestations
question
What is larva migrans
answer
Dog and cat ascarid larvae (Toxocara spp.) hatched from eggs that are accidentally swallowed
Larvae migrate and encyst as second-stage larvae, terminating development
Produces tracts with hemorrhagic necrosis and eosinophilic and lymphocytic infiltration
Can migrate to the liver causing enlargement and studded nodules
question
How is Ascaris lumbricoides (Roundworm) diagnosed?
answer
Eggs in stool (negative in early infection)
question
How is Necator americanus and Ancylostoma duodenale (Hookworm) contracted?
answer
Direct contact (walking barefoot) or ingestion of soil contaminated with human fecal matter
question
How does a Necator americanus or Ancylostoma duodenale (Hookworm) infection progress?
answer
On contact with the human host, the larvae penetrate the skin and are carried through the veins to the heart and then to the lungs. They penetrate into the pulmonary alveoli, ascend the bronchial tree to the pharynx, and are swallowed
Larvae reach the small intestine, where they reside and mature into adults. Adult worms live in the lumen of the small intestine, where they feed on erythrocytes of the host.
question
What are the symptoms of Necator americanus and Ancylostoma duodenale (Hookworm)?
answer
Infecting larvae induce pruritic maculopapular dermatitis at site of entry ("ground itch")
Transient pneumonitis
Epigastric pain, inflammatory diarrhea with eosinophilia
Primary Syndrome: Iron deficiency anemia
Occult blood in stool
Larva migrans
question
How is Necator americanus and Ancylostoma duodenale (Hookworm) diagnosed?
answer
Eggs in fresh stool, larvae in old stool
question
How is Strongyloides stercoralis (Threadworm) contracted?
answer
Direct contact of contaminated soil (walking barefoot) or ingestion of contaminated soil
question
How does a Strongyloides stercoralis (Threadworm) infection progress?
answer
? Colonization of bowel and maturation
? Can spread through lymphatics to blood stream and other organs leading to abscesses, granulomas, or sepsis
Can cause reinfection by maturing in bowel and re-entering through skin in perianal region
question
What are the symptoms of a Strongyloides stercoralis (Threadworm) infection?
answer
"Ground itch", cough and Loeffler’s syndrome, chronic watery diarrhea with mucous, may contain blood, urticaria, Larva currens
question
What is Larva currens?
answer
• Occurs on the trunk or near the anus and is a linear eruption in which the larvae migrate under the skin causing an itchy, non-indurated wheal with a red flare that moves rapidly and disappears in a few hours
question
What are the cestodes (tapeworm)? What are their features?
answer
Taenia solium (pig tapeworm)
Taenia saginata (beef tapeworm)
Have proglottids and Cystercerci (tissue cysts)
question
How are Cestodes (tapeworms) and Taenias contracted? How does the infection progress?
answer
Ingestion of cystercerci in meat
Ingestion of eggs
Invasion of tissues and cystercerci formation, most commonly in brain
question
What are the symptoms of a Cestode (tapeworms) or Taenias infection?
answer
Likely to be asymptomatic
Epigastric discomfort
Nausea
Sensation of hunger
Diarrhea
Cysticercosis if eggs are ingested
question
How are Cestode (tapeworms) or Taenias diagnosed?
answer
Detection of eggs or proglottids in stool
Cystercerci: plain films reveal calcified “puffed rice” lesions
question
How are Trematodes (Fluke) contracted?
answer
Biliary infections: Ingestion of poorly cooked, pickled, or smoked fish
Liver infections: Ingestion of metacercariae encysted on aquatic plants (watercress)
question
How does a trematode (fluke) infection progress in the biliary tract?
answer
Excyst in small intestines, migrate through ampulla of Vater into biliary ducts
Worms lead to adenomatous hyperplasia, inflammation, and duct obstruction
question
How does a trematode (fluke) infection progress in the liver?
answer
Excyst in duodenum, pass through intestine into peritoneum, invade liver through Glisson’s capsule
Granulomatous reactions, duct obstruction, etc. may occur
question
How does a biliary trematode (fluke) infection manifest?
answer
Acute infections noted by fever, eosinophilia, and hepatomegaly
Heavy worm burden may lead to constitutional complaints and symptoms associated with cholelithiasis and pancreatitis
question
How does a liver trematode (fluke) infection manifest?
answer
Fever, hepatomegaly and/or abdominal pain
Nausea, cough, diarrhea, and urticaria are also common
Periods of jaundice
question
How is a biliary trematode (fluke) infection diagnosed?
answer
Ova can be identified in stools, dilation of ducts by imaging
question
How is a liver trematode (fluke) infection diagnosed?
answer
Fever, hepatomegaly or liver pain, proper clinical setting
Serology, as ova may not be detected in stool
question
What are the general characteristics of Staphylococcus aureus?
answer
Ferments mannitol, coagulase-positive, catalase-positive
Gram-positive, cocci in clusters
Non-motile, non-sporeformer
Facultative anaerobe
question
What causes Staph aureus food poisoning?
answer
Results from bacterial toxin in food, not an infection by the bacteria itself
question
What foods are commonly contaminated by Staph aureus?
answer
Usually by improper handling of meats
Ham, salted pork (can grow in high salt content
Custard-filled pastries
Potato salad
Ice cream
question
What are the toxins secreted by Staph aureus?
answer
Enterotoxin A and B
Can lead to severe metabolic alkalosis
question
What types of media are capable of culturing Staph aureus
answer
?-hemolytic sheep’s blood agar

Selective media:
Mannitol salt agar
Phenylethylalcohol agar (PEA
question
What are the general characteristics of Clostridium perfringens
answer
Gram-positive, spore-formers
Can be found in the intestinal flora of humans and in the soil
question
How is Clostridium perfringens food poisoning contracted?
answer
Ingestion of contaminated food via dirt or feces
Often occur in institutions or after large gatherings, can incubate at moderate temps
Most commonly in meat cooked in bulk and then left in warming trays
question
What increases the likelihood of food poisoning by Clostridium perfringens?
answer
The longer the meat is allowed to sit, more likely of getting sick
question
What types of media are capable of culturing Clostridium perfringens?
answer
EYA (egg yolk agar) with anti-toxin A in ? of the plate: precipitation forms around colonies to indicate lecithinase activity

Double-zone of hemolysis on blood agar
question
How does Clostridium perfringens cause food poisoning?
answer
Heat-labile enterotoxin
question
What are the effects of clostridium enterotoxin?
answer
Maximum effect in the ileum
Minimum effect in the duodenum
Inhibits glucose transport
Damages intestinal epithelium
Causes protein loss into the intestinal lumen
question
What causes Enteritis necroticans?
answer
Clostridium perfringens, type C
question
How is enteritis necroticans contracted?
answer
Occurs after large consumption of improperly cooked pork during native feasts
question
What are the symptoms of Enteritis necroticans?
answer
Severe necrotizing disease of the small intestine
Intense abdominal pain, distension, bloody diarrhea, vomiting & shock
High mortality due to intestinal perforation
question
How does Clostridium botulinum cause food poisoning?
answer
Ingestion of secreted botulin toxin
question
What are the effects of botulin toxin?
answer
Small amounts can produce paralysis and death
Attaches to neuromuscular junction of affected nerves
Prevents release of acetylcholine
Approximately 1 microgram of toxin is lethal
question
What is the most common route of botulin toxin food poisoning?
answer
Home-canned vegetables
question
What is the progression of botulin intoxication?
answer
Cranial nerve paralysis
Respiratory muscle weakness which can be fatal
Preceding or following onset of paralysis
question
How is botulin toxin food poisoning diagnosed?
answer
Presence of organism and/or toxin in vomitus, gastric fluid, or stool
question
How is botulin toxin food poisoning treated?
answer
A-B-E antitoxin
Can slow progression of disease but will not neutralize toxin already bound to neuromuscular junctions
question
What are the possible pathologies caused by Bacillus cereus food poisoning?
answer
Gastroenteritis
Ocular infections
Intravenous catheter-related sepsis
Diarrhea syndrome
Vomiting syndrome
question
What are the general characteristics of Bacillus cereus?
answer
Spore-former
?-hemolytic on sheep blood agar
Facultative anaerobe
Motile, gram-positive rod
question
How does Bacillus cereus food poisoning cause diarrhea syndrome?
answer
Enterotoxin produced, adenylate cyclase is activated in intestinal cells
Similar to action of cholera toxin
question
What foods are associated with Bacillus cereus induced diarrhea syndrome?
answer
Spaghetti sauces
Dried potatoes, dried milk
Foods are maintained at temperatures between 30-50 degC
question
What foods are associated with Bacillus cereus induced vomiting syndrome?
answer
Fried rice via a heat stable toxin that does not activate adenylate cyclase
Large amounts can lead to liver failure
question
What are the toxins secreted by Bacillus cereus?
answer
Heat-stable, proteolysis-resistant enterotoxin: Emetic form
Heat-labile enterotoxin: Diarrheal form
question
How is Bacillus cereus food poisoning diagnosed?
answer
Samples of contaminated food must be cultured
Identification in stool specimens of symptomatic patients is strong evidence
Grows rapidly on sheep blood aga
question
Cryptosporidium spp. infections are associated with what mode of contraction?
answer
Contaminated water
question
What are the general characteristics of Cryptosporidium spp.?
answer
A coccidian, subphylum, Sporozoa (protozoan)
Lives on or just below the epithelial cells of the small intestine
question
What is significant about the life cycle of Cryptosporidium spp.?
answer
Asexual reproduction allows for continued autoinfection, oocysts are infective when passed
Patients may remain infective after diarrhea ceases
question
What are the symptoms of a Cryptosporidium infection?
answer
Frequent, watery diarrhea
Nausea, vomiting
Abdominal cramps
Low-grade fever
question
How does Cryptosporidium cause diarrhea?
answer
Alters osmotic pressure in the gut resulting in in influx of fluid, much like cholera
Epithelial cells are damaged by
Invasion of parasite
T-cell mediated inflammation causing villus atrophy
question
How is Cryptosporidium infections diagnosed?
answer
Modified Ziehl-Nielsen acid-fast stain
Microscopic observations of small, acid-fast oocysts in smears of fecal specimens
question
How is Cryptosporidium treated?
answer
Self limiting in most
If immunocompromised, give Paromomycin
question
What are the general characteristics of Giardia lamblia?
answer
Flagellate
Most commonly identified intestinal parasitic pathogen
Cysts are resistant forms, survive in cold water for several months
question
How is Giardia lamblia most commonly acquired?
answer
Contaminated water and person contact in institutions or daycare centers
question
Describe the lifecycle of Giardia lamblia
answer
Trophozoites reproduce by longitudinal, binary fission in the lumen of the proximal small bowel
Encystation occurs as parasites travel to the colon
Cysts are passed out through nondiarrheal feces
question
What are the symptoms of acute Giardiasis?
answer
Diarrhea, abdominal pain, bloating, nausea, vomiting
question
How is Giardia lamblia diagnosed?
answer
Microscopic identification of cysts or trophozoites in feces
question
How is Giardia lamblia treated?
answer
Metronidazole, tinidazole
question
How is Entamoeba histolytica (a pathogenic amoeba) infection most commonly contracted?
answer
Oral/fecal route, contaminated water, food
Cysts are found in formed stools
Can survive for day-weeks in external environment, trophozoites die in the acidic stomach
question
What are the characteristics of invasive, intestinal amebiasis via Entamoeba histolytica?
answer
Dysentery, colitis
question
What are the characteristics of extra-intestinal amebiasis via Entamoeba histolytica?
answer
Liver abscess
Peritonitis
Pleuropulmonary abscess
Cutaneous and genital amebic lesions
question
What is the mechanism of GI infection by Entamoeba histolytica?
answer
Mediated by an adherence lectin in instestin
Disruption of intestinal barrier by secretion of proteolytic enzymes and invasion of intestinal epithelial cells
question
What are the characteristic appearance of Entamoeba histolytica GI lesions?
answer
Flask-shaped ulcers
question
E. histolytica is resistant to what immune mechanisms?
answer
Phagocytosis
Complement-mediated cell lysis
question
What are the consequences of a heavy infection of Entamoeba histolytica?
answer
Causes vacuoles to coalesce
Sloughing off of the lining causes bloody, mucus-filled stools
question
How does Entamoeba histolytica cause liver abscesses?
answer
May completely erode the intestinal mucosa
Enters the circulation
Organ most commonly colonized is the liver, causes abscess formation
question
How does Entamoeba histolytica cause lung abscesses?
answer
Penetration of the diaphragm from hepatic abscesses or from hematogenous spread
question
How is Entamoeba histolytica diagnosed?
answer
Microscopic evidence of trophozoites in stool specimens via wet mounts or trichrome-stained smears
Sigmoid biopsies
ELISA provides evidence of current infection but is not diagnostic
question
What are the general characteristics of Cyclospora cayetanensis?
answer
Spore-forming coccidia
Unicellular, coccidian parasite
Oocysts are passed in stools, not infective, distinguishes this organism from Cryptosporidium
Sporulation occurs in the environment at temp. between 22-32 degC
question
How is Cyclospora cayetanensis most often transmitted?
answer
Fresh produce and water via contamination with sporozoites released asexually into the stool
question
How is Cylcospora cayetanensis infection prevented?
answer
Can be killed by washing or cooking
Occurs primarily in the tropics and subtropics
question
How is a Cylcospora cayetanensis infection diagnosed?
answer
Evidence of oocysts in stool specimens by microscopy
Stool specimens should be refrigerated or preserved in 10% formalin
Requires 3 or more specimens collected at 2-3 day intervals due to intermittent release of oocysts
Modified acid-fast stain
question
What are the symptoms of a Cylcospora cayetanensis infection?
answer
Watery diarrhea which can be severe
Anorexia, nausea, vomiting, abd pain
Low-grade fever, fatigue
Flu-like symptoms
Can persist for several weeks
question
How are Cylcospora cayetanensis infections treated?
answer
Usually self-limiting in both immunocompetent and immunocompromised individuals, give fluids
Trimethoprim-sulfamethoxazole can reduce symptoms
question
What is Blepharitis?
answer
Noncontagious inflammation of the lower portion of the eyelids and eyelashes caused by
Poor eyelid hygiene
Excess oil
Staphylococcus aureus
Allergic reaction
question
What is Dacryocystitis?
answer
Inflammation of the lacrimal sac caused by partial or complete obstruction within the sac or nasolacrimal duct
Bacteria are trapped initiating acute or chronic infection
Older patients are predisposed
question
What is Conjunctivitis?
answer
Inflammation of the conjunctiva, the outermost layer of the eye covering the sclera
Progressive keratitis can lead to ulceration, scarring, and blindness
question
What are the three causes of conjunctivitis?
answer
Bacterial (most common) viral, or allergies
question
What are the characteristics of viral conjunctivitis?
answer
Usually due to an upper respiratory infection
Watery discharge
Red eye
Irritation
Can spread to other eye
question
What symptoms of bacterial conjunctivitis help differentiate it from viral conjunctivitis?
answer
Stringy discharge
Other symptoms:
Swelling of the conjunctiva
Redness, tearing
Irritation (gritty feeling)
Can spread to other eye
question
What is the most common cause of bacterial conjunctivitis?
answer
Adults: Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae
Infants: Neisseria gonorrhoeae, Streptococcus pneumonia, Haemophilus influenzae
question
How do you treat bacterial conjunctivitis?
answer
Antibiotic ointments or eyedrops
Neomycin, polymyxin, bacitracin
Gentamicin, tobramycin against gram-neg microorganisms
question
What is Ophthalmia neonatorum?
answer
Severe conjunctivitis of newborns, can acquire the infection at birth, typically due to STD pathogens
Neisseria gonorrhoeae, Chlamydia trachomatis, Herpes simplex virus
question
What is Endophthalmitis? What causes it?
answer
Rare, intraocular infection of the aqueous or vitreous humor caused by normal flora of the eyelids:
Staphylococcus epidermidis
Rarely by pseudomonas (poor prognosis)
question
What is Uveitis?
answer
Inflammation or swelling of the eye structures responsible for the eye’s blood supply
question
What are the symptoms of Iritis (anterior uveitis)?
answer
Redness, pain, photophobia due to painful movement of inflamed iris
Blurred vision in severe inflammation
question
What are the symptoms of Intermediate uveitis (cyclitis)?
answer
Blurring, presence of floaters (black dots or wispy lines which move across the field of vision)
question
What are the symptoms of posterior uveitis
answer
Blurring, gradual or sudden reduction in vision
Usually painless
question
What is periorbital cellulitis? what are potential complications?
answer
Acute infection of the tissues surrounding the eye
Can lead to orbital cellulitis and protrusion of the eyeball, meningitis if severe
question
What causes periorbital cellulitis?
answer
Absence of an effective drainage system, predisposes the parasinuses to invasion
Bacteria, fungi, or parasites can gain access via trauma, surrounding infection, or upper respiratory infection
question
Haemophilus influenza is grown on what type of media?
answer
Chocolate agar
Requires the 2 erythrocyte growth factors X (hemin)
and V (nicotinamide adenine dinucleotide) for growth
question
What is the appearance of Haemophilus influenza?
answer
Gram-negative, bacillus (rod)
Non-motile, non-spore forming
Fastidious, facultative anaerobe
question
What mediates pathogenesis for Haemophilus influenza?
answer
Attachment to respiratory epithelial cells is accomplished using pili
Endotoxin in the cell wall is toxic to ciliated respiratory cells
question
What is the most virulent strain of H. influenza which is responsible for infections such as bacteremia, meningitis, cellulitis, septic arthritis, and pneumoniae?
answer
Haemophilus influenzae type b (HiB)
question
Which H. influenza strain causes mucosal infections such as otitis media, conjunctivitis, bronchitis, and pneumoniae?
answer
Nonencapsulated (or non-typeable) strains
80% of individuals are colonized with the non-typeable strains
COPD and cystic fibrosis pts particularly susceptible
question
What are the general characteristics of Streptococcus pneumonia
answer
Gram-positive, cocci
Usually seen in pairs**(diplo) but not always
Non-spore formers, non-motile
question
Strep pneumonia is cultured on what media?
answer
Blood agar medium results in alpha-hemolysis (partial hemolysis)
Can grow very quickly under optimal conditions
question
What determines the virulence of Strep pneumonia?
answer
Capsule interferes phagocytosis by blocking C3b opsonization
question
What is the Quellung reaction?
answer
Serotyping used to identify a particular capsule type of strep pneumo
Antibody reacts with a particular capsule type, causes capsular swelling
question
What allows Staph aureus to avoid phagocytosis?
answer
Protein A, a cellular component in the cell wall
question
What are the virulence factors of Staph aureus?
answer
Cytolytic toxins (alpha and beta hemolysin, staphylococcal leukocidin)
Enzymes (coagulase, hyaluronidase, lipase)
Protein A
question
How do you differentiate Staph epidermidis from Staph aureus?
answer
Staph epidermidis is coagulase-negative whereas Staph aureus is positive
question
What type of infections are caused by Staph epidermidis?
answer
Hospital acquired UTIs
Osteomyelitis at prosthetic joints
Native valve endocarditis due to catheters
Bacteremia
Almost ALL cases of infection are hospital acquired
question
What mediates the antibiotic resistance of Staph epidermidis?
answer
Plasmid-mediated, can also transfer to Staph aureus
question
What are the general characteristics of Chlamydia trachomatis?
answer
Obligate intracellular parasites
Most common STD in the world, causes blindness and infertility
question
What is trachoma?
answer
Chlamydia infection of the eye transmitted through eye secretions and eye-seeking flies
Inflammatory reactions results in scarring on the conjunctiva
Eyelid to turns inward where the eyelashes can rub the cornea
question
What is unique about the life cycle of Chlamydia trachomatis?
answer
Alternates between a non-replicating, infectious elementary body and a replicating, noninfectious reticulate body
question
How is Chlamydia trachomatis diagnosed?
answer
Immunofluorescence
question
What is MOTT?
answer
mycobacteria other than tubercle bacilli
Associated with contact lenses, trauma, and wound contamination with soil
Causes Keratitis and Corneal ulcers
question
What are the most common MOTT pathogens?
answer
Mycobacterium chelonae
Mycobacterium fortuitum
question
What are the general characteristics of Eikenella corrodens?
answer
Microaerophilic, gram-negative rods
Normal flora of human, mucosal surfaces
Culture requires CO2 environment and hemin in the medium, lab must be notified in advance
Usually a part of a mixed infection with Streptococcus sp.
Gets its name from the fact that it forms pits on the surface of agar medium
question
How is Francisella tularensis contracted?
answer
Primarily a pathogen of squirrels and rabbits. Humans are infected by the bite of an infected deer fly or tick
or eating undercooked infected meat or handling infected rabbit carcasses
question
What are the symptoms of tularemia (Francisella tularensis infection)
answer
Highly infectious
Skin ulcers
Swollen, painful lymph nodes
Inflamed eyes, sore throat, mouth sores
question
How is Francisella tularensis cultured?
answer
Grown on chocolate agar
question
What causes "cat scratch fever"?
answer
Bartonella henselae: Gram-negative bacillus
question
What are the characteristics of cat scratch fever (Bartonella henselae infection)?
answer
Parinaud’s Oculoglandular Syndrome, manifests as conjunctivitis, neuroretinitis
Vitritis, posterior uveitis
Discrete foci of retinitis manifested as white retinal or choroidal lesions
question
What are the characteristics of HSV blepharitis?
answer
Vesicles appear on lid margins and around the eyes
Vesicles can break open forming lesions which can become superinfected by skin flora
question
What is ocular herpes and what are its characteristics?
answer
HSV infection of the conjunctiva
Swelling of the eyelids
If cornea is involved (Herpes Simplex Keratitis)
Destructive ulceration and perforation of the cornea possible
question
What is Herpes Simplex Keratitis?
answer
Dendritic keratitis
Secondary herpetic infections
Virus branches out in a dendritic pattern**
Virus deadens the nerves – no pain
question
What are the characteristics of varicella-zoster blepharitis?
answer
Vesicles may appear on the lid margins
Wartlike lesions can form (molluscum contagiosum) from the pox virus
Can cause keratitis, scleritis, infections of the lacrimal apparatus, endophthalmitis
question
What ocular infections are caused by adenovirus?
answer
Conjunctivitis and epidemic keratoconjunctivitis
question
What are the characteristics of CMV retinitis?
answer
Floaters, flashes, and blind spots
Pizza pie retinopathy (CMV infiltrates the vascular endothelium)
More common among immunocompromised or neonates from infected mothers
question
What are the characteristics of Aspergillus sp?
answer
Most commonly encountered genus of fungi in the clinical laboratory
Erects conidiophores from a “foot cell” with a vegetative hyphae
question
What are the characteristics of Acremonium sp.?
answer
Filamentous fungi isolated from plant debris and soil
Rare cases of keratitis and endophthalmitis
Known to cause opportunisitic infections in immunocompromised
Possess fine, narrow, septate hyphae
question
What are the characteristics of Penicillium sp.?
answer
Filamentous fungi
Found in soil, decaying vegetation, air
May cause infections in immunocompromised hosts
Has a bottle brush look
Can cause Keratitis and Endophthalmitis
question
What are the characteristics of Rhizopus sp?
answer
Causative agent for a group of fungal infections classified as zygomycosis, frequently fatal
Causes rhinocerebral infections
Also known as the black bread mold
question
What predisposes someone to a rhinocerebral infection?
answer
Diabetic ketoacidosis
Immunosuppression
question
Nosocomial rhinocerebral infections are usually contracted through what means
answer
Contaminated adhesive tape
Contaminated, wooden tongue depressors
question
What is responsible for approximately 90% of rhinocerebral infections classified as zygomyosis?
answer
Mucormycosis
question
What causes endophthalmitis due to candida infections?
answer
Exogenously following surgery or trauma (rare)
Endogenoushly due to embolic seeding in the retina (most common cause)
question
What pathogens can cause corneal ulcers due to improper contact lens use?
answer
Pseudomonas, Bacillus cereus, Acanthamoeba
question
Keratitis due to Acanthamoeba is associated with what kind of behavior?
answer
Wearing of nondisposable lenses
Use of homemade sodium chloride solutions
Wearing of contacts while swimming
question
Toxoplasma gondii is most often contracted via what vectors?
answer
Exposure to contaminated water containing tissue cysts
Exposure to oocysts shed by infected cats
Eating meat contaminated with oocysts
Congenital transmission
question
Congenital infections by Toxoplasma gondii targets what organs?
answer
Retina (chorioretinitis)
Brain
question
What are the different morphological forms of Toxoplasma gondii?
answer
Oocysts in intestines of members of the cat family (primary host)
Tachyzoite – the invasive form responsible for acute disease
Sporulated and unsporulated oocysts
question
How is Toxoplasma gondii diagnosed?
answer
Indirect immunofluorescent assay (IFA)
Ring enhancing lesions on imaging is indicative
question
How is Loa loa (eyeworm) transmitted?
answer
Chrysops fly
Confined to the rain forest and swamp forest areas of West Africa
question
How is Onchocerca volvulus transmitted?
answer
Spread by the vector, Simulium (the black fly)
question
What is caused by infection by Onchocerca volvulus?
answer
River Blindness
Microfilaria can migrate into peripheral blood and the eyes during heavy infections, infects the cornea, optic nerve, choroid
Dead microfilaria induce an inflammatory response in the eyes
question
What causes Myiasis?
answer
Infection of tissues or organs of animals or man by fly larvae
Oestrus ovis (sheep botfly)
Can cause severe conjunctivitis
question
What are the most common manifestations of a hematological infection?
answer
Anemia
Pancytopenia
Lymphocytosis
Neutrophilia
Eosinophilia
question
What is Pancytopenia?
answer
A decrease in all blood cell lineages due to toxic effects causing bone marrow necrosis, inflammatory mediators, and hemophagocytic syndrome
question
What causes Pancytopenia?
answer
Congestive splenomegaly due to infections such as:
Salmonellosis, infectious mono
Tularemia, hepatitis
Syphilis
Toxoplasmosis
Schistosomiasis, malaria
question
What is Tularemia?
answer
AKA glandular fever, rabbit fever, tick fever, and deer fly fever
Caused by infection by Francisela tularensis acquired from the bite of an infected tick (Ixodes, Dermacentor)
question
What are the general characteristics of Francisela tularensis?
answer
Gram-negative, non-motile rod
Strict aerobe, fastidious
Intracellular parasite
Acquired from the bite of an infected tick (Ixodes, Dermacentor)
question
What is the most common clinical manifestation of Tularemia?
answer
Ulceroglandular tularemia
Skin lesion (from a tick bite) is a painful papule which ulcerates having a necrotic center
Leads to lymphadenopathy and bacteremia
question
How is Tularemia diagnosed?
answer
Direct immunofluorescent staining
question
What causes Toxoplasmosis?
answer
Toxoplasma gondii, an intracellular blood and tissue parasite
Definitive host is the cat
Infective oocysts are shed in cat feces
Human infection is due to ingestion of improperly cooked meat or oocysts from cat feces
question
What is the infective form of Toxoplasma gondii?
answer
Trophozoites
Responsible for initial infection and tissue damage
question
What are some of the more rare causes of Toxoplasmosis?
answer
Transplacental infections
Transfusion infection via contaminated blood
question
T. gondii has a predilection for infecting which organs?
answer
Heart and lymphoid organs especially
Lung, CNS, and eyes as well
question
An infant suffering from a congenital case of Toxoplasmosis experiences what symptoms?
answer
Anemia
Jaundice, epilepsy, encephalitis, other neurological disorders
question
What are the symptoms of Hemophagocytic Syndrome (aka hemophagocytic lymphohistiocytosis (HLH))
answer
Fever, splenomegaly*
Jaundice
Presence of activated macrophages phagocytizing erythrocytes, leukocytes, platelets, and other blood cell precursors
Phagocytosis is detectable in the bone marrow
question
What is reactive hemophagocytic syndrome?
answer
Hemophagocytic syndromes secondary to an underlying infection
question
Sporadic and familial cases of HLH are caused by what?
answer
Acute infections
question
Hemophagocytic Syndrome can interfere with the diagnosis of what treatable infectious disease?
answer
Visceral leishmaniasis
question
What initial diagnostic tests should be performed if Hemophagocytic syndrome is suspected?
answer
Blood and urine cultures
Chest radiography to screen for tuberculous infections
Serological assays for viral infections
Throat and rectal swabs for viral culture
Fungal antigen testing
Determine if an underlying T-cell lymphoma is present
question
Hemophagocytic syndrome is associated with HIV patients with what kind of underlying infections?
answer
Pneumococcal disease
Pneumocystosis
Histoplasmosis
question
What kind of infections associated with animal infections or travel need to be considered in cases of hemophagocytic syndrome?
answer
Leshmaniasis
Brucellosis
Rickettsioses
Malaria
question
What are the most common symptoms of hemophagocytic syndrome?
answer
Fever*, splenomegaly*
question
What are the most common lab abnormalities associated with hemophagocytic syndrome?
answer
**Anemia, thrombocytopenia, neutropenia, hypertriglyceridemia, hypofriboginemia
question
How can the overactivation of macrophages cause hemophagocytic syndrome (HLH)?
answer
High levels of activating cytokines due to viral or nonviral causes
Associated with EBV infection and the presence of episomal EBV genome in T cell lymphocytes
question
What is Brucellosis?
answer
Infection caused by Brucella sp.
question
What are the general characteristics of Brucella sp.?
answer
Small, nonmotile, gram-negative rods
Requires complex growth media
Strict aerobe
Slow growth (at least 1 week)
An intracellular parasite of the reticuloendothelial system
question
What are the two types of colony morphology of Brucella? What is it based off of?
answer
Based on the O antigen of LPS
Smooth (translucent, homogeneous, more virulent)
Rough (opaque, granular, or sticky)
O chain of the smooth strain LPS is a marker for virulence
question
Describe the pathogenesis of Brucella
answer
An intracellular parasite of the reticuloendothelial system
Microorganisms are phagocytosed by macrophages and monocytes
Acidic environment of the phagolysosome induces virulence genes
Phagocytosed bacteria are carried to the spleen, liver, bone marrow, lymph nodes, and kidneys, forms granulomas
question
How is Brucellosis contracted?
answer
Consuming contaminated, unpasteurized milk and other dairy products
question
What is Leishmaniasis? What causes Leishmaniasis?
answer
Infection by Leishmania sp.
Vector-borne disease transmitted by sandflies
question
What causes the symptoms of a Leishmania infection?
answer
Amastigote forms found in reticulo-endothelial cells of the viscera
Spleen, lymph nodes, liver, intestines
question
What is distinctive about the incubation period of Leishmaniasis?
answer
Incubation can be as short as 10 days or as long as a year
question
What are the symptoms of Leishmaniasis?
answer
Anemia, protrusion of abdomen due to splenomegally, and bleeding mucus membranes are most important*
Low grade fever, malaise, wasting, facial edema, diarrhea, breathing difficulties
question
What causes Rickettsioses?
answer
Rickettsia sp.
Transmitted by tick vectors
question
What are the general characteristics of Rickettsia?
answer
Obligate intracellular, aerobic, gram-negative rods
question
How is Rickettsia diagnosed?
answer
Giemsa stain is preferred
question
Describe the pathogenesis of Rickettsia?
answer
Enters eukaryotic cells by stimulating phagocytosis
Degrades the phagosome membrane using a phospholipase to enter the cytoplasm, necessary for survival
question
What is the characteristic site of pathologic lesions of Rocky Mountain Spotted Fever?
answer
Small blood vessels
Vessels may be blocked by thrombi causing vasculitis in the heart*, spleen*, skin, liver, kidneys, lungs, or CNS
question
Severe cases of Rocky Mountain Spotted Fever are in danger of what complication?
answer
Disseminated Intravascular Coagulopathy (DIC)
question
What is Rocky Mountain Spotted Fever
answer
Rickettsioses due to Rickettsia rickettsii transmitted through the tick
question
What is Epidemic typhus?
answer
Rickettsioses caused by Rickettsia prowazekii transmitted by exposure to human body louse feces (Pediculus humanus)
question
What are the symptoms of epidemic typhus?
answer
Splenomegaly*, hypotension*, vascular collapse* if severe
High fever, headache, maculopapular rash
question
What is Scrub typhus?
answer
Rickettsioses caused by Rickettsia tsutsugamushi
Transmitted to humans by chigger (mite larva) bites
Occurs in Asiatic-Pacific areas
question
What are the clinical symptoms of scrub typhus?
answer
*Splenomegaly, *interstitial myocarditis
Fever, headache, macular rash
Delirium, stupor, muscle twitching
question
What causes increased levels of hepcidin with release of cytokines in cases of anemia due to chronic infection?
answer
Iron is trapped in the reticuloendothelial system
Erythropoietin levels decrease
Cytokines suppress hematopoiesis in the bone marrow
question
What is the function of Hepcidin?
answer
Key regulator in iron metabolism
Regulates absorption of iron from foods and iron transport across the placenta
Regulates the release of iron from macrophages and the recycling of aged RBCs
question
How does inflammation affect the actions of Hepcidin and cause anemia?
answer
Production is 100x higher than normal
Results in increased sequestration of iron in macrophages
question
What are the best known parasitic infections that cause hemolytic anemia?
answer
Malaria (Plasmodium falciparum)
Bartonellosis (Bartonella bacilliformis)
Babesiosis (Babesia microti)
question
What causes malaria?
answer
Sporozoites of Plasmodium falciparum in the salivary glands of mosquitoes that have ingested blood infected with malarial gametocytes
question
Describe the pathogenesis of Plasmodium falciparum (malaria)
answer
Sporozoites travel to the liver where they invade and replicate
Merozoites leave the liver through the circulatory system and invade red blood cells
Merozoites continue to replicate, lyse RBCs, and invade other RBCs
question
Plasmodium falciparum (most severe form of Malaria) feeds on what?
answer
Hemoglobin and other proteins
Ultimately causes destruction of the spleen
Merozoites adhere to glycophorin molecules on the red blood cell surface
question
Which organisms cause relapsing malaria?
answer
Plasmodium vivax and Plasmodium ovale
After treatment, treatment-resistant parasites reside dormant in the liver
Eventually they invade RBCs and begin a typical erythrocytic cycle
question
Which organism causes long-lasting malarial infections that are most often asymptomatic?
answer
Plasmodium malariae
question
RBCs parasitized by Plasmodium vivax display small purplish red granules (with Wright’s stain) called what?
answer
Schuffner’s dots
question
How is malaria diagnosed?
answer
Giemsa or Wright stains are gold standard
question
What are other forms of malarial diagnosis?
answer
Malarial RDTs (rapid diagnostic test)
question
What is Babesiosis?
answer
Zoonosis caused by animal-specific protozoan parasites
Parasites invade RBCs and induce a febrile disease
Hemolytic anemia, hemoglobinuria, shock, death
question
What Babesia species are responsible for majority of human infections?
answer
Babesia microti
Babesia divergens
question
What are the most common hosts for Babesia?
answer
White-footed mouse
Deer tick
Humans are accidental hosts, no human to human transfer
question
How is Babesiosis diagnosed?
answer
Direct blood smears show tetrad formation in RBCs
Indirect fluorescent antibody test
question
What is Oroya fever (acute)?
answer
Infection by Bartonella bacilliformis (Bartonellosis)
Motile by polar flagellum
Adheres to and invades RBCs
question
What causes Bartonellosis (Oroya fever)?
answer
Transmitted by the nocturnal sandfly
Limited to a small area in the Andes Mountains
question
How does intraerythrocytic Bartonella bacilliformis avoid the immune response?
answer
Lacks MHC molecules on the surface of mature erythrocytes
Presentation of Bartonella antigens to the immune system is not possible
question
How is Bartonellosis diagnosed?
answer
Serologic testing
Microscopic examination of Giemsa-stained blood smears
question
What alpha toxin is secreted by Clostridium perfringens?
answer
Lecithinase
question
*What are the actions of the alpha-toxin lecithinase secreted by Clostridium perfringens?
answer
Reacts with red blood cell membrane lipoproteins to produce lysolecithin
Disrupts cell membranes of host cells including Erythrocytes and Leukocytes
Mediates massive hemolysis, increased vascular permeability, and bleeding
Causes myocardial dysfunction
question
What is the action of Theta-toxin (?-toxin) secreted by Clostridium perfringens?
answer
Is a heat-labile & oxygen-labile hemolysin
Alters capillary permeability
Toxic to heart muscle
Pore-forming (cytolytic)
question
What is responsible for initial cell destruction in respiratory tract by Clostridium perfringens?
answer
Hydrogen peroxide
Damages erythrocyte membranes*
question
How does Mycoplasma pneumoniae cause cold autoimmune hemolytic anemia?
answer
Auto-IgM antibodies are directed against the I antigen on red blood cells
Cause agglutination of RBCs* transiently in the fingers, ears, nose
question
Mycoplasma pneumoniae is inherently immune to what types of antibiotics?
answer
Beta-lactams due to lacking a cell wall
question
What are the general characteristics of Mycoplasma pneumoniae?
answer
Slow rate of growth
Obligate aerobe
Receptor on Mycoplasma pneumoniae is integral in attachment to eukaryotic host cell membranes in the respiratory tract and RBCs
question
What are the possible complications of measles vaccination?
answer
Thrombocytopenia*
question
What are the characteristics of a Rubella infection?
answer
Respiratory transmission
Viruses replicates in the nasopharynx & lymph nodes
Viremia* with spread to other tissues
question
What are the hemorrhagic manifestations* of a Rubella infection?
answer
Rare, primarily children
Low platelet count, vascular damage
Thromobocytopenic purpura
GI, cerebral, intrarenal hemorrhaging can occur
question
What are the IgG antibodies that react with RBCs in the cold (below body temperature)
answer
Donath-Landsteiner antibodies cause a rare form of cold-autoimmune hemolytic anemia referred to as Paroxysmal cold hemoglobinuria
Can be idiopathic or associated with Syphilis, Varicella, Mumps, Measles, etc.
question
What kind of infection can cause Ag/Ab complexes bind to RBC surface and induce hemolysis?
answer
Hemophilus influenzae type b meningitis
question
What is Polyagglutination?
answer
A rare form of hemolysis caused by metabolites from infectious agents forcing RBCs to exposed normally hidden surface antigens
Example: enteric bacteria can produce neuraminidase
question
What kinds of infections can cause a disruption of the gastrointestinal or genitourinary mucosa leading to anemia by blood loss?
answer
Helicobacter pylori
Helminthic infections such as nematodes and trematodes
question
What is the most cause for blood loss anemia in developed countries?
answer
H. pylori
question
How do Ancylostoma duodenale & Necator americanus (hookworms) cause blood loss?
answer
Due to feeding worms
Microcytic, hypochromic anemia develops
question
Describe the pathogenesis of Schistosomiasis?
answer
Cercaria penetrate the skin and enter the venous system
Travel to heart, lungs, and portal circulation
question
What are the symptoms of Acute schistosomiasis (Katayama’s fever)
answer
*Diarrhea (bloody), *Hepatosplenomegaly, *eosinophilia, Cystitis, ureteritis with hematuria* (can lead to bladder cancer)
Fever, cough, abd pain, occasional CNS lesions, pulmonary hypertension
question
How is Fasciolopsis buski (intestinal fluke) contracted?
answer
Ingestion of encysted larva in aquatic vegetation like water chestnuts
Found only in China, Vietnam, Thailand, parts of Indonesia, Malaysia, India
question
Attachment of the flukes (Fasciolopsis buski) to the small intestines causes what?
answer
Hemorrhage*
Marked eosinophilia*
Inflammation and ulceration
question
What parasite causes Megaloblastic Anemia?
answer
Diphyllobothrium latum (Cestode)
(Fish tapeworm)
Common in areas where raw or pickled fish are eaten
question
What is characteristic of carriers of Cestodes (fish tapeworm) suffering from megaloblastic anemia?
answer
Low serum levels of vitamin B12
question
What are the characteristics of Trypanosoma?
answer
Flagellated, insect-transmitted protozoa that infects RBCs and tissues
question
What causes Chagas’ Disease?
answer
Trypanosoma cruzi transmitted by feces of Triatomine (reduviid) bugs, the "kissing bug"
question
What are the acute symptoms of Chaga's disease?
answer
Romana’s sign: Eye on one side swells (at location where triatomine bug fecal matter gets rubbed in)
Occur in about 1% of cases
question
What are prolonged symptoms of Chaga's disease?
answer
Enlarged liver or spleen*
Fever, fatigue, swollen lymph glands
Brain damage and death in younger
question
What causes African Sleeping Sickness?
answer
Trypanosoma brucei gambiense (slow progressing)
Trypanosoma brucei rhodesiense (rapidly progressing)
Kinetoplastids (mitochondrial DNA)
question
What is characteristic of the acute blood stage of infection for African Sleeping Sickness?
answer
Fever, headaches
question
What causes relapses of African Sleeping Sickness?
answer
Antigenic variation of trypanosomal surface
Life cycle exhibits different morphologies
question
What are the symptoms of African Sleeping Sickness?
answer
Apathy, fatigue, confusion, motor changes (tics, slurred speech)
Changes in sleep patterns
Extreme fatigue during day, extreme agitation during night
question
What are potential complications of African Sleeping Sickness?
answer
Trypanosomes cross the blood-brain barrier resulting in meningoencephalitis
Untreated can progress to coma or death
question
What is Filariasis?
answer
Caused by infections with nematodes (roundworms)
Infective larvae are transmitted by arthropods
question
How do nematodes (roundworms) cause filariasis?
answer
Female worms produce microfilariae
Microfilariae enter and circulate in the bloodstream
question
What are the clinical manifestations of lymphatic filariasis?
answer
Eosinophilia is prominent*
Many are asymptomatic though some develop lymphatic dysfunction
question
How is filariasis diagnosed?
answer
Identify presence of microfilariae in blood
Blood collection must be timed with periodicity of organism
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