lect 17: E. coli

e. coli, shigella, salmonella

pathogens in the family enterobacteriaceae

indole positive, lactose fermenter

important biochemical test results that help distinguish E. coli from other GNR

soil, vegetables, water, undercooked meat

environments where facultative anaerobic GN bacteria are found

intestinal pathogenic e. coli (IPEC)

E. coli causes diarrhea with onset more than 16hrs after ingestion

extra intestinal pathogenic E. coli (ExPEC)

E. coli causes UTIs, bacteremia, peritonitis, pneumonia, and meningitis, virulence determinant capsule allows translocation outside of GI tract

virulence determinants

intestinal pathogenic e. coli (IPEC), acquisition enables pathogenesis

uropathogenic e. coli (UPEC)

most common extra intestinal site of infection, second most common cause of hospitalization behind pneumonia, most common underlying infection leading to bacteremia, 10 clones responsible for UTIs

type 1 and P pili

allows uropathogenic e. coli (UPEC) adherence to epithelial cells

cytotoxic necrotizing factor CNF

uropathogenic e. coli (UPEC), toxin disrupts intracellular signaling and cytoskeleton

enterotoxogenic E. coli (ETEC)

E. coli is single most important cause of travelers diarrhea, disease is mediated by LT and ST toxins

travelers diarrhea

diseased mediated by enterotoxogenic E. coli (ETEC) toxins

heat labile toxin (LT)

enterotoxogenic E. coli (ETEC) AB subunit toxin, increases cAMP in gastrointestinal epithelium leading to Cl and water secretion and inhibition of NaCl uptake leading to watery diarrhea

heat stable peptide toxin (ST)

enterotoxogenic E. coli (ETEC) toxin stimulates guanylate cyclase leading to increased cGMP leading to Cl and water secretion and inhibition of NaCl uptake

cGMP

ETEC heat stable peptide toxin (ST) stimulates guanylate cyclase increasing … production

cAMP

ETEC heat labile toxin (LT) increases… production in gastrointestinal epithelium

10^8

enterotoxogenic E. coli (ETEC) infectious dose

enterohemorrhagic/shigatoxin producing E. coli (EHEC/STEC)

E. coli strains with shiga toxin causes bloody diarrhea due to localized damage to GI epithelium

shiga toxin

enterohemorrhagic/shigatoxin producing E. coli (EHEC/STEC) AB subunit toxin is released from bacteria and delivered into host

localized damage to GI epithelium

allows enterohemorrhagic/shigatoxin producing E. coli (EHEC/STEC) to systemically deliver stx (shiga toxin)

gb3 expression

host factor bound by shiga toxin B subunit, expression is greater in children leading to children getting infected by EHEC/STEC more frequently than adults

hemolytic uremic syndrome (HUS

triad of thrombocytopenia, anemia, renal insufficiency caused by shiga toxin from enterohemorrhagic/shigatoxin producing E. coli (EHEC/STEC)

enterohemorrhagic e coli (EHEC)

present in 99% of cattle who are not susceptible to shiga toxin, diarrheal outbreaks associated with contaminated produce, raw dairy products, and undercooked beef

100

enterohemorrhagic e coli (EHEC) infectious dose

contaminated produce, raw dairy products, undercooked beef

enterohemorrhagic e coli (EHEC) diarrheal outbreaks are associated with…

proper cooking temperature, proper refrigeration, hand washing

best way to prevent enterohemorrhagic e. coli (EHEC) infection from contaminated produce/raw or undercooked beef products

gram stain

main method of diagnosing e coli infection

enteric pathogens multiplex nucleic acid test

diagnostic test detects multiple GI pathogens including all phenotypes (EPEC, ETEC, EHEC, STEC, etc)

rehydration, bismuth subsalicylate

treatment for watery diarrhea infections

rehydration

treatment for bloody diarrhea

loperamide

should avoid this for treating bloody diarrhea, worsens severity and increases risk of systemic complications

antibiotics

should avoid this for treating bloody diarrhea, causes release of shiga toxin (stx)

antibiotics, loperamide, non steroidal anti inflammatory drugs

treatments/drugs you should avoid for treating bloody diarrhea