Bacterial Causes of Diarrhea – Flashcards

- may not have any diarrhea or vomiting

- dysentary may be present

- fecal leukocytes present

- blood in stool

- fever

1. Salmonella sp.
2. Shigella sp.
3. Campylobacter sp.
4. Yersinia enterocolitica
5. Vibrio parahaemolyticus
6. Francisella tularensis
7. EIEC
8. EHEC

Gram -, rods, motile, facultative anaerobes, non-lactose fermenting

Habitat:

- typhi = human

- enteritidis and choleraesuis = intestines of animals

Fecal-oral route

animals to humans (Turtles)

animal food products to humans

-sensitive to killing by gastric acid

-attach to gastric epithelial cells in sm. intestine and colon -> bacterial type III secretory system injects bacterial proteins into host cells -> internalization -> replication in vacuoles -> cell lysis -> enter mesenteric lymph nodes and blood stream -> fever, ab pain, diarrhea

used by Salmonella sp.

-bacterial needle that injects effector proteins into host cell

-inflammatory diarrhea due to invasion of intestinal epithelial cells

-controlled by vagocytic defenses

-risk in immunocompromised for disseminated disease

-cause enteric fever (typhoid fever)

-fever, nonproductive cough, bloody diarrhea, ab pain, rose spots on skin

-invasive intracellular pathogen

-reaches blood stream (better than other Salmonella sp.)

-little diarrhea

-enteric fever

-involvement of other organs

- most common form of salmonellosis

- symptoms occur 6 - 48 hrs after injestions

• nausea, ab cramps, vomiting, nonbloody diarrhea
• fever, headache, myalgias

Symptoms last 2 days - 1 wk

- higher risk in pediatric, geriatric and immunocompromised

- clinical presentation like all Gram (-) sepsis

S. typhi = typhoid fever

others = paratyphoid fever

-bacteria pass through the gastric epithelial cells and are engulfed by macrophages

-Symptoms:

• 10 - 14 days after ingestions
• fever, headache, myalgias, malaise, anorexia for 1 wk followed by diarrhea

Non-lactose fermenter = colorless on MacConkey agar

motile

H2S+

enteritidis - isolated from stool

typhi - isolated from stool OR blood

fewer rectal leukocytes than shigellosis

General:

Gram -, bacilli, non-motile, non-lactose fermenter

resistant to stomach acids = only 10 - 20 bacilli needed to cause disease

Habitat:

human and primate intestines

invades and survives in cytoplasm

Transmission:

fecal-oral, P2P

-produces shiga toxin (exotoxin, cytotoxic to epithelial cell)

-attach and penetrate GI epithelial cells and M cells (use Type III)

-multiply intracellularly, spread to contiguous cells (use hemolysin to escape cell)

-use host cell actin for transport

-isolation from stool

-nonlactose fementer

Distinctive features from Salmonella:

-non-motile

-H2S negative

-incubation period 36 - 72 hrs

-fever, cramping ab pain (both non specific)

-dysentary 2 days later

-watery diarrhea

-usually self limited

-prevent P2P spread

-fluid and electrolyte replacement for severe cases

-antidiarrheal compunds contraindicated (b/c they inhibit peristalsis = can't get rid of toxin)

General:

gram -, curved or comma shaped, microaerophilic, motile rods

can suvive intracellularly in monocytes and intestinal epithelial cells -; tissue necrosis and cell death

can travel to blood stream

;

habitat: intestinal tract of animals

;

transmission:

-fecal-oral route

-transmitted ny contraminated food; more common in summer

leading cause of bacterial diarrheal illness in US

;

most common cause in udnerdeveloped countries

;

3-5 days after ingestion; diseasse only if penetrates the mucouse layer and invades GI epithelial cells

-flagella

-adherence factors

-heat labile toxin = watery diarrhea

-ingestion by host cells = inflammatory colitis

-can also produce shiga toxin

-inflammatory and bloody diarrhea

anywhere from 7 days to chronic infection

;

periumbilical cramping, intense abdominal pain that mimics appendicitis, malaise, myalgias, headache, vomiting

;

watery diarrhea = most common

;

inflammatory bowel disease

Detection:

-WBC in feces

-isolation in stool: requires growth on Campy or Skirrow media

;

general:

aerobic, gram (-), bacilli

;

habitat: domestic and farm animals

;

transmission: fecal-oral route

invades mucosa of terminal ileum -; painful enlargement of mesenteric lymp nodes

- mistaken for appendicitis

- causes inflammatory and bloody diarrhea

;

transmitted by contaminated meat products, mostly during winter (can grow at 4 degrees C)

virulence:

-heat stable enterotoxin -; inflammatory and bloody diarrhea

;

clinical:

-febrile illness with abdominal pain

-can mimic appendicitis

-lasts 2 - 3 weeks

-common in infants, occasional septicemia

gram (-), motile, bacilli

;

found in fresh, salt and chlorinated water habitats

;

very resistant to temperatures and chemicals

;

Aerolysin cytotoxic toxin (ACT)

;

opportunistic pathogen in immune compromised

virulence:

-produces cholera toxin - activates adenylate cyclase to increase cAMP -; voluminous, watery diarrhea

;

transmission:

-contaminated water or food (shellfish or crabs)

-colonizes small bowel

-acute illness due to enterotoxin production

;;; -severe form: rapid loss of liquid and electrolytes; hypovolemic shock, metabolic acidosis and death

-acid sensitive = requires a lot to cause disease

- A-B type toxin

- A increases adenylate cyclase activity -; increase in cAMP

-abrupt, watery diarrhea (rice water)

-vomiting following diarrhea

-cyanotic, sunken eyes, high voice, unobtainable BP, etc. all because of severe dehydration

-rice water stools

-stool culture on thiosulfate-citrate-bile salt-sucrose agar (TCBS); colonies are yellow, other Vibrio are green

-hemolytic strains are most virulent

-enterotoxin production -; moderate bowel inflammation; mild to moderately severe diarrhea

-halophilic (salt-loving); grows in marine environments

-found in raw or undercooked shellfish

-colonizes small intestine

Transmission:

-ingestion of inadequately cooked seafood or sushi

;

clinical: watery diarrhea, ab cramps, nausea, vomiting, bloody diarrhea (sometimes)

;

diagnosis: green on TCBS agar

-Non-invasive = do not see fecal WBC's

-colonize sm. intestine

-common cause of traveler's diarrhea

-produce cholera-like (heat-labile) toxin and a heat-stable toxin -; both lead to watery diarrhea (secretion of Cl- -; osmotic diarrhea)

-abrupt onset watery diarrhea, lasts less than 24 hrs after initiation of fluid replacement

-non-invasive = do not see WBC in stool

-no known toxin

-adheres to epithelial cells in Sm. intestine and disrupts microvilli (effacement)

-type III secretory system

;; -makes its own receptor

;;;;;;; - when it binds to cell it forms pedestals

-watery diarrhea with mild inflammation, infants ;6 m.o.

-non-invasive = do not see WBC in stool

3 stages:

1. adhere to mucosa
2. enhanced mucus production encases bacteria enabling biofilm formation
3. elaboration of cytotoxin, damages intestinal cells

-may colonize sm. and lg. intestine

-cause of a more persistent diarrhea

Diagnosis:

-isolation on MacConkey's Agar (like Vibro)(lactose fementer)

Tx: fluid and electrolytes, antibiotics

-similar pathogenesis as for Shigella infections

-results in watery diarrhea and dysentery

-sporadic outbreaks in infants and children

-mostly infects lg. bowel

-kidney damage due to Shiga toxin

Clinical manifestations:

-Hemolytic colitis: severe crampy ab pain, watery diarrhea followed by bloody diarrhea, no fever

-Hemolytic Uremic Syndrome: triad of acute renal failure, thrombocytopenia and microangiopathic hemolytic anemia

Dx:

-carbohydrate sorbitol must be included in the medium

-inability to ferment sucrose

-ELISA detection of Shiga Toxins 1 and 2 in stool

Tx: Avoid antibiotics

-usually mild diarrhea but systemic symptoms are prominent

-pathogen can break into cytoplasm and divide

-major risk is maternal infection during pregnancy

-serious in immunocompromised

• MOST common in uncomplicated outpatient UTI's
• Gram (-), motile, bile tolerant, lactose fermenting
• Lab ID: pink on MacConkey Agar
• transmission: part of normal flora

• adherence to urethroepithelial cells via fimbriae (pyelonephritis strains are the most adherent)
• endotoxin
• some strains have capsule adhesion

UPEC

• adhere to urethroepithelial cells
• increased serum resistance
• increased hemolysin production

• 5-15% of cystitis cases in young, sexually active women
• gram (+), cocci in clusters
• transmission: normal flora of skin and GU mucosa
• prevention: urination after intercourse

• white colonies on blood agar
• catalase (+)
• coagulase (-)
• mannitol non-fermenter
• Novobiacin resistant (distinguishes from other coagulase (-) staph)

• nosocomial UTI pathogen
• white colonies on blood agar
• Catalase (+)
• Coagulase (-)
• mannitol non-fermenter
• novobiacin sensitive

• Pathogenesis: slime production and biofilm formation; colonizes catheters and prostheses
• Tx/Px: MDR strains exist so use catheter care

• common in pts with recurrent infections, instrumented or have anatomic defects
• normal flora of UG tract
• MDR (vanco)
• fomerly classified in Streptococcus

• produces ureases which cause pyelonephritis
• Highly motile (swarmer) - able to ascend the ureter against the flow of urin
• Gram (-), rod

Virulence Factors:

• urease
• endotoxin

Lab ID:

• non-lactose fermenting
• urease (+)
• indole (-)

• common in pts with recurrent infections, instrumented or have anatomic defects
• Gram (-) rod, motile
• lactose fermenter
• MDR

• common in pts with recurrent infections, instrumented or have anatomic defects
• nosocomial pathogen
• inherently resist to many antibiotics
• Gram (-), rods, motile, aerobe
• ubiquitous distribution in soil and water

• oxidase (+) (distinguishes from E. coli)
• pigment production
• fimbriae for adherence
• endotoxin
• biofilm formation (attaches to catheters)

• nosocomial UTIs
• Gram (-), non-motile, lactose fermenter
• Transmission: normal flora, able to survive in moist environments (hands)
• virulence: capsule, endotoxin, fimbriae

• gram (-), bacillus, facultative anaerobe
• normal GI flora in small numbers
• environmental bacteria
• opportunistic pathogen (nosocomial)
• characteristic red pigment
• lactose - , indole - , urease - , motile, H2S -

• common in hospitalized pts who are on broad-spectrum antibiotics and have a bladder catheter
• diabetic pts
• immunosuppressed pts