GI- Microbiology – Flashcards
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Unlock answers| How can infection cause anemia? |
| bacterial infections suppress erythropoietin production and the proliferation of erythroid progenitors; and also chronic infections impair iron utilization |
| Lab results for Iron in anemia of chronic disease |
| low sFe, reduced TIBC, and abundant stored Iron in tissue macrophages |
| Cause of pure red cell aplasia |
| B19 virus |
Infections that lead to aplastic anemia (4 viruses) |
| hepatitis virus, CMV, EMV, and HSV |
Infections that lead to hemolytic anemia (2 parasites) |
Bebesia leads to cell lysis Leishmania causes production of oxidative metabolic products that lyse RBCs |
| Bacterial toxins that might cause toxin production |
- alpha toxin in Clostridium perfringens - Capsular polysaccharide (PRP) of hameophilus influenza type B binds red cell surface and anti-PRP antibodies lyse the cell |
| Parasitic infection which causes microcytic anemia |
| iron deficiency anemia, associated with Hook Worm |
| Infections that lead to megaloblastic anemia |
| B12 deficiency accompanying D. Latum infection |
B19 presentation in various hosts (child, adult, chronic hemolytic anemia, immunocompromised patient, fetus) |
fifth's disease polyarthropathy transient aplastic crisis (TAC) PRCA Pure red cell aplasia congenital anemia, hydrops fetalis |
B19 virus and anemia (target; cell, presentation) |
erythroid progenitor cells;and erythroblasts, blood group antigen P erythema infectiosum, arthalgia, arthritis |
| What is transient aplastic crisis, what is the presentation;and what infection is it associated with? |
TAC is the abrupt cessation of erythropoiesis reticulocytopenia, absent erthyroid precursors in the bone marrow and precipitous worsening of anemia B19 associated TAC is found in patients with underlying hemolytic disorders or in patients with high RBC turnover |
| If a pregnant woman in her second trimester is exposed to parvovirus B19, what thest should be done first? |
| obtain IgG and IgM serology ASAP |
What would each of the possible serology results of pregnant woman in her second trimester indicate/ - positive IgG result and negative IgM - positive IgG and IgM - negative IgG and positive IgM - negative IgG and negative IgM |
- indicates past infection (no risk to fetus) - indicates infection with in the last 1-120 days (possible risk to fetus) - indicates acute infection (higher risk to fetus) - indicates the mother is not immune and that no evidence of acute infection is noted.; Repeat the test in three weeks. |
Treatments for the following anemias: - pure red cell aplasia - aplastic crisis - HIV |
- intravenous immunoglobulin (IVIG) - packed RBCs - HAART |
| Two target cells of Malaria parasites leading to anemia |
P.vivax binds Duffy blood group antigen P. falciparum binds to sialic acid residues on glycophorin A |
Babesia microti (transmission, population, acute and chronic presentation) |
tick-transmitted protozoan immunocompromised inclusions- tends to form ring froms in tetrads acute- malaise, headache, chills, sweating, periodic fatigue chronic- hemolytic anemia, renal failure |
| Symptoms of Hook Worm infrection |
often asymptomatic iron (microcytic) deficiency anemia respiratory symptoms, itch, edema |
D. Latum (associated anemia, other symptoms, diagnosis) |
B12 deficiency leading to megaloblastic anemia salt craving, intermittent abdominal discomfort detection of large operculated eggs in stool or recovery of proglottids |
Bartonella bacilliformis (Gram stain, different disease presentations) |
gram-negative rods that penetrate RBCs carrion disease- acute febrile illness oroya fever- severe anemia verruga peruana- blood-filled nodules |
| 5 common features of H. pylori and C. jejuni |
- spiral or curved shape - gram negative rods - low G-C bqase ratio - inability to ferment or to oxidize carbohydrates - microaerophilic |
H. pylori (urease, H2S production, nitrate reduction, growth at 42 C, shape, size) |
positive negative negative negative spiral with 3 unipolar flagella 1 x 4 um |
C. jejuni (urease, H2S production, nitrate reduction, growth at 42 C, shape, size) |
negative positive positive positive bipolar flagella not very wide |
| Describe the symptoms associated with a C. jejuni infection |
up to 10 stools/day bloody diarrhea RUQ pain- often only symptom |
| Describe the symptoms of a C. fetus infection |
endocarditis, septic thrombophlebitis arthritis spetic abortion, meningoencephalitis, spontaneous peritonitis |
| hyatid cysts in the liver |
| Echinococcus granulosus |
| biliary obstruction |
| Ascaris lumbricoides |
| Treatment of Campylobacter Infections |
fluid and electrolyte replacemnet empirical antibiotics for patients with high fever or bloody or frequent diarrhea erthromycin clears in 72 hours |
| Virulent factor of H. pylori |
| O-side chain resembles the blood group antigens so serve to protect the bacteria from immune clearance |
| selequae of h. pylori |
| gastric ulcers, MALT (mucus associated tissue lymphoma) |
| treatment for H. pylori |
PPI clarithromycin beta-lactams |
| bacteria found in scondary periotinitis caused by appendicitis perforation |
| Prevotella melaninogenica |
| Most important cause of endemic severe diarrheal illness |
| Rotavirus group A |
Rotavirus (S/Sx, D, T) |
over a week duration ELISA/Latex agglutination in stool samples severe if ass. w/ dehydration and electrolyte imbalance vaccines are available |
| Explain the role of the NSP4 protein in rotavirus in causing diarrhea |
intracellular release of Ca leading to diarrhea disrupts tight junction allowing for paracellular flow of H2O and electrolytes sitmulates the ENS |
| Name three virulence factors of adenovirus |
inhibition of MHC I expression E proteins- block apoptosis by binding Rb and p53 VA-RNAS block interferon anti-viral response |
| General characteristics of Enterobacteriaceae |
Gram-negative rods motile and facultative anaerobes LPS is the major cell wall antigen |
| Distinguish between typhoid and non-typhoid serovars of Salmonella |
typhoid serovars: human-to-human, fecal-oral non-typhoid: animal or contaminated food handling |
| Summarize virulence factors employed by Salmonella to establish infection |
attachment to epithelial cells by fimbriae; invade through M cells and enterocytes replication occurs in the endocytic vacuole; disseminated infection can occur enterotoxin produced |
| Define; MacConkey Media |
bile salts and crystal violet inhibit gram-positive fermentation of lactose produces pink |
| Describe EMB Media |
Eosin blue and methylene blue inhibit the growth of gram positives blue or green with lactose fermentation |
| Discuss the mechanism by which Shigella invades intestinal epithelial cells |
invades M cells of the colon by type III secretion invades neighbor cells by comet-like actin tail IL-1 release and PMN migration causes further loss in cell integrity ; |
| Define the mechanism of action of Shiga toxin |
AB subunit is cleaved by the protease furin the A subunit inhibits protein translation by cleaving 28S rRNA this causes cellular damage to intestinal epithelium |
ETEC (site of action, disease, pathogenesis ; virulence factors) |
small intestine Traveler's diarrhea enterotoxins stimulate hypersecretions of fluids and electrolytes, colonization factor antigens |
EHEC (site of action, disease, pathogenesis & virulence factors) |
large intestine hemolytic-uremic syndrome shiga toxin disrupts protein synthesis. A/E lesions on microvilli results in decreased absorption. Bfp, intimin adhesion |
EIEC (site of action, disease, pathogenesis & virulence factors) |
diarrhea which progresses to dysentery with bloody stools invasion mediated by invasive plasmid antigen |
| Explain how SMAC media aids in the diagnosis of E.Coli. |
| E. coli O157:H7 (EHEC) is the only E.coli strain that does not ferment sorbitol |
| What is the cause of Hemolytic Uremic Syndrome? |
| Shiga toxin form EHEC damages kidneys which release erythropoietin |
Yersininae enterocolitica (general characterisitics, source, CF, Labs) |
gram - rod, intracellular, cold tolerant contaminated meat gastroenteritis involving distal ileum, colon, and mesenteric lymph nodes, possible sequelae of autoimmune disorder lactose negative, urease negative, motility at cold temperatures |
After three days of vacationing in the city of Lima, Peru, a newly married couple fall ill with what appears to be the same condition. Both experience vomiting, watery diarrhea, nausea, and abdominal cramps. An analysis of their stool results in the isolation of gram-negative rods which produce colonies on MacConkey that are pink Which of the following is the most likely causative microorganism? |
| E. coli (is a lactose fermenter) |
| A 28-year-old woman complains of painful swelling of the right knee and and tender skin eruptions on both shins. For the past two weeks she has also had watery diarrhea that developed after she consumed some raw pork. She also complains of low-grade fever and mild abdominal pain. Both red and white blood cells were observed in her stool sample. A stool sample revealed a gram-negative rod that was only motile at temperatures below 30°C. Clear colonies on MacConkey agar |
| Yersiniae enterocolitica ( motility below 30 C) |
| A 16-year-old boy is brought to the emergency room by his parents, as he has been experiencing bloody diarrhea for 1 week. He also complains of not urinating often and blood in his urine when he does. His laboratory studies demonstrate an increased BUN and creatinine and the presence of gram-negative rods which produce beige colonies on SMAC and colonies on EMB as shown below (green). The condition is associated with infection by which of the following E. coli types? |
| EHEC (beige on SMAC) |
| A 36-year-old man comes to the emergency room because of the development of sudden nausea, vomiting, and diarrhea with blood and mucus, as well as crampy abdominal pain. He had just returned yesterday from a business trip to South America and has been experiencing these symptoms for two days. Leukocytes were found in his stools as well as a gram-negative non-motile rod. Growth on MacConkey media after 48 hours shows clear colonies. Which of the following is the most likely causative microorganism? |
| Shigella dysenteriae (non-motile, non-lactose fermenter) |
| A 3-year-old man presents with sudden-onset, crampy abdominal pain and diarrhea. The diarrhea is watery and contains mucus. The patient also complains of low-grade fever with chills, malaise, nausea, and vomiting. Careful history reveals that he had ingested partially cooked eggs at a poultry farm 24 hours before his symptoms began. Based on this limited information, which of the following microorganism would you most likely suspect? |
| Salmonella enterica (sudden, mucus, poultry) |
| A 3-month-old female infant was brought to the emergency department of a general hospital with a 5-day history of decreased activity, decreased oral intake, upper airway congestion, and general irritability. There was no history of fever or vomiting. During the previous 2 weeks, she had been constipated, and twice her mother had given a tablespoon of honey for treatment. The physical examination revealed dry oral mucosa, a sluggish pupillary response, and significant hypotonia. A gram stain of the fecal sample revealed a gram positive spore forming rod. Which of the following is the most likely diagnosis? |
| C. Botulism (flaccid paralysis) |
| A 67-year-old man presented with fever, abdominal cramping, and frequent diarrhea for four days. Three weeks before the current episode, he had undergone a hip replacement and was rehabilitating in an orthopedic unit. During the hospitalization, he developed a nosocomial pneumonia and was treated empirically with clindamycin. He gradually improved and was discharged a week before his current presentation, with maintenance oral antibiotics. Which of the following is the most likely diagnosis? |
| Shigella sonnei (nosocomial infection) |
C. difficile (CF, and A and B toxins) |
pseudomembranous colitis A- enterotoxin--> recruits PMNs B- causes cytoskeletal damage |
C. perfringens (LF and A and B toxins) |
lechtinase enzyme destoys cells causes precipitate growth on egg yolk agar A enterotoxin disrupts ion transport B enterotoxin forms pores--> bloody diarrhea |
C. botulism (CF, source) |
1-3 days of weakness, blurred vision, and constipation flaccid paralysis canned foods |
| Specifics about two forms of Bacillus Cereus |
emetic and diarrheal form diarrheal form lasts longer, from meat and is heat labile |
Giardia lambia (transmission, symptoms, E, D) |
fecal-oral diarrhea, increased fat and mucus in stool worldwide, primarily human-to-human transmission cysts (stain with Trichrome stain)and smiley-face trophozoite (stain with Kohn and Giemsa stain) forms are detected in feces |
| What stain is diagnostic for Cryptosporium? |
| acid-fast stain, it won't stain with trichrome |
| What is the treatment for cryptosporidium infection? |
| hydration, no drugs; are effective against crypto |
Cryptosporidium (Et, Sx, E, D); |
fecal-oral frothy BMs, anorexia, self-limiting, immunocompromised pateints cannot self cure oocysts, acid fast stain |
Balantidium coli (E, Sx, E, D) |
fecal-oral intermittent diarrhea with blood and pus, ulceration worldwide, swine #1 animal reservoir microscopic exam, bean-shaped macronucleus |
| How does the O/P of E. histolytica read? |
| trichrome stain shows ingested red blood cells |
E. histolytica (Et, Sx, E, D) |
fecal-oral dysentery, RUQ worldwide, human-to-human microscpic exam, motile trophozites PCR differentiate histolytica from dispar |
| O/P of Ascaris lumbricoides |
| large, mamillated coat and tapered end in fertilized egg |
| O/P of stengyloides stercoralis |
| muscular neck, distinguished from hookworm by mouth at one end and notched tail on the other |
| O/P of schistosoma mansoni |
| large spine projecting out of one side |
| Life cycle of ascaris lubricoides |
ingested eggs travel to the lunges larvae break free in 3 weeks larvae pass and can be swallowed back into the small intestine |
| O/P of trichus trichiura |
| white worm , barrel shaped eggs with mucoid plugs at both ends |
Trichuris trichiura (Et, Sx, E, D) |
fecal-oral diarrhea, rectal prolapse in children Worldwide concentrated microscopic specimen |
Schistosoma mansoni (Et, Sx, E, D) |
skin penetration by cercariae from snails dermatitis, enlarged liver and lymph nodes, eosinophilia and dysentery South America and Africa schistosome eggs in stool and urine |
