bacterial gasteroenteritis Flashcards
Describe the epidemiology and pathogenesis of enterohemorrhagic E. coli. Distinguish the various forms of E. coli infections. Differentiate E. coli and Salmonella using culture media. Diagnose Salmonella infections Describe the clinical characteristics and epidemiology of cholera. Identify the mechanism of action of cholera toxin. Compare Campylobacter and E. coli infections. Characterize the microbial cause of ulcers.
predominant aerobe in the gut
e coli
noninflammatory diarrhea
watery, large volume stools with no blood, pus or severe pain
inflammatory diarrhea
lower volume stools with blood,pain, pus and fever
enterotoxins cause
noninflammatory diarrhea
cytotoxins cause
inflammatory diarrhea
definition of coliform
lactose positive
fecal pathogens that are lactose negative
salmonella and shigella
gram negative rod, ferments lactose
e coli
red colonies on macConkey indicate
lactose fermentor
habitat of e coli
GI tract of vertebrates and soil/water contaminated with feces
virulence factors of e coli
Pili Locus for Enterocyte Effacement Type 3 Secretion System LT/ST enterotoxins Shiga Toxin
MOA of LT toxin
ribosylates adenylyl cyclase –> increases cAMP –> causes secretion of water and electrolytes –> diarrhea
MOA of ST toxin
increases cGMP –> increases cAMP –> causes secretion of water and electrolytes –> diarrhea
produces shiga toxin
enterohemorrgagic e coli (EHEC) (O157:H7)
MOA of shiga toxin
inhibits protein synthesism provokes apoptosis –> capillary thrombosis and mucosal inflammation –> hemorrhagic colitis
bad end result of shiga toxin
hemolytic uremic syndrome
primary resivoir of e coli (O157:H7)
cattle gut
most important early virulence factor of EHEC
type III seretion lesion causing attaching and effacing lesions
intense abdominal pain, bloody diarreha, no or slight fever
EHEC
ID of e coli (O157:H7)
lactose positive colonies that do not ferment sorbitol, then test for O157 and H7 antisera
sx of HUS
acute renal failure, hemolyic anemia and thrombocytopenia
What NOT to EVER do in EHEC infection
give antibiotics (releases shiga toxin)
remains extra cellular, attached by lesions and injects toxin by integreated bacteriophage
e coli EHEC
causes watery diarrhea in bottle fed infants in developing countries
Enteropathic E coli (EPEC)
causes “traveler’s diarrhea”
enterotoxigenic e coli (ETEC)
“traveler’s diarrhea” very similar to
cholera