Enterics Flashcards
E. coli
facultative G- rod pink on MacConkey's agar strong lactose fermenter green-black on eosin-methylene blue agar indole + antibios used in the young, chronically ill, and pt with extra-intestinal infections
E. coli Virulence
adhesion factors, fimbria, pili LT toxin --> ADPR xsferase; inc cAMP ST --> inc cGMP cytotoxins (EHEC) capsule Type III secretion system endotoxin
ETEC
Vir: LT or ST
traveler’s diarrhea
childhood diarrhea
water, nonbloody, non inflammatory diarrhea
EPEC
Vir: adherence to enterocytes
infantile and childhood diarrhea in developing countries
water, nonbloody diarrhea with minimal WBCs
EHEC (O157:H7)
Vir: verotoxin shiga-like toxin
hemorrhagic colitis
hemolytic uremic syndrome
bloody, noninflammatory diarrhea
EIEC
Vir: invasion of enterocytes
purulent, bloody diarrhea with prominent WBCs
Vibrio cholera
G- comma-shaped rods oxidase + motile Dx via isolation and culture from stool sample
V. cholera virulence
Cholera toxin –> ADPR-xsferase (A-B subunits)
adhesion factors and mucinase
V. cholera patho
rice water stools
infection starts in ileum and spreads
massive dehydration and electrolyte imbalance if left untreated
Vibrio parahemolyticus
halophilic marine org
diarrheal disease in Japan and cruise ships
raw or undercooked seafood
diarrhea can be bloody; usually self limiting
Vibrio vulnificus
halophilic marine org
Gulf Coast shellfish
causes severe cellulitis; esp in shellfish handlers
rapidly fatal septicemia in immunocomp
chronic liver dz predisposes to severe inf
C. diff
G+ spore-forming rod obligate anaerobe found in soil and also NF of colon antibiotic-assoc diarrhea psuedomembraneous colitis
C. diff virulence
glucosylxsferases the inactivate members of Ras superfamily of small GTPase
Toxin A: enerotoxin; fluid sec and hemorrhagic necrosis
Toxin B: cytotoxin; cell rounding
detect Toxin B in stool for Dx
Shigella spp
bacillary dysentery G- rod lactose non-fermenter H2S- non-motile
Shigella virulence
Shiga toxin --> heat labile inhib port synthesis sim to EHEC verotoxin invasion plasmid antigens endotoxin Type III sec system
Shigella patho
inf starts in SB and moves to LB
invasion and penetration of epith cells
prod microabscesses and shallow, crater-like ulcers
inflammatory diarrhea –> mucoid and bloody with tenesmus
Salmonella virulence
facultative intracellular invasins Vi antigen --> antiphago Endotoxin --> O polysacch chains Type III Sec system
Salmonella typhi
typhoid fever penetrates to serosa layer feel sick on first week rose spots second week (maybe) bloody diarrhea third week may develop carrier state in sec and stool can metast to bone, joint, liver, and meninges Tx with antibio
Salmonella enteritidis and typhimurium
enterocolitis contam poultry and such invade intestinal mucosa N/V/Diarrhea (nonbloody) 8-48hrs after ingestion self limiting isolate organ from stool
Salmonella cholerasius
bacteremia with focal lesions
follows oral infection
may result in osteomyelitis, pneumonia, meningitis
Sickle cell pt most at risk
Salmonella spp
G- rod lactose non-fermenter H2S postitive motile Dx via stool samples for enterocolitis Dx via blood 1st and 2nd wks for typhoid Widal test
Campylobacter jejuni
G- rods oxidase + microaerophilic can grow at 42deg short, curved MAJOR cause of diarrhea --> enterocolitis
C. jejuni patho
watery, foul smelling diarrhea
bloody stools may follow
self limiting after 5-8d
Complication: Guillian-Barre Syndrome
Yersinia enterocolitica and pseudotuberculosis
G- rod facultative anaerobe xsmit via con tam food or water or direct inoculation start inf in ileum enterotoxin sim to ST of e. coli seen in children a lot self-limiting
