E. Coli Flashcards
what are the main serogroups of Enterohemorrhagic E. coli (EHEC, STEC)?
O157:H7 O111 O26 O157:H- O104:H4
what are the sources of EHEC & STEC infection?
food (undercooked/unpasteurized)
petting zoos
person to person
very low infectious dose
Describe Enterrohemorrhagic (EHEC & STEC) clinical syndrome.
abdominal pain bloody diarrhea can lead to hemolytic uremic syndrome acute renal failure (usu. children <10) generally extracellular
Describe Enterrohemorrhagic (EHEC & STEC) pathogenesis - what tools does the bacteria have to cause disease?
pili-mediated attachment T3SS Intimin recruit host cell actin causing altered morphology shiga-like toxin capsule
What are the aspects of Enterrohemorrhagic (EHEC & STEC) virulence - what does it do in the body to cause disease?
- actin disruption results in altered morphology and impacts signal transduction pathways forming A/E lesions
- lesions lead to loss of microvilli (effacement)
- Shiga like toxin disrupts eukaryotic protein synthesis and causes hemolytic uremic syndrome
- hemolysin
what is Tir? what does it allow E. coli to do?
a T3SS secreted bacterial protein that is delivered to surface of epithelial cells to allow for E. coli attachment
what is Intimin? (E. coli)
Tir binding protein on surface of E. coli
what is Shiga-like toxin? how is it toxic?
gene found on phage
disrupts eukaryotic protein synthesis via RNA cleavage activity
causes hemolytic uremic syndrome
what is Hemolysin? (E. coli) where is it encoded?
pore forming protein that inserts into host cell membrane
encoded by a plasmid
what are the Diarrheagenic strains of E. coli?(5)
Enteropathogenic (EPEC) Enterotoxigenic (ETEC) Enteroaggregative (EAEC) Enteroinvasive (EIEC) Diffuse adhering (DAEC)
How is Enteropathogenic E. coli (EPEC) transmitted?
Overt human pathogen transmitted by person-to-person contact
How it Enterotoxigenic E. coli (ETEC) transmitted?
From food and water
what type of e. coli produces a heat-labile toxin? how does this toxin act? what is the clinical consequence?
Enterotoxigenic E. coli (ETEC)
- targets adenylate cyclase leading to increased cAMP levels that result in excess chloride ion secretion and blocked sodium ion uptake
- leads to net loss of fluid and electrolytes in gut and watery diarrhea
what type of e. coli produces a heat-stable toxin? how does this toxin act? what is the clinical consequence?
- Enterotoxigenic E. coli (ETEC)
- alters cGMP levels leading to fluid and electrolyte loss through watery diarrhea
what types of disease does Enteroaggregative E. coli (EAEC) cause?
- Diarrheagenic
- Childhood diarrhea/Chronic diarrhea
- persistent diarrhea that can lead to weight loss
- No A/E lesions
how is Enteroinvasive E. coli (EIEC) transmitted?
From contaminated food
what diseases does diffuse adhering E. coli (DAEC)? in what types of patients and where? what is know about it?
Diarrhea in older children in developing countries
poorly characterized
how would you diagnose E. coli?
- what would you see in a lactose test?
- sorbitol test?
- immunoassay?
- PCR?
- Lac+
- O157:H7 cannot grow on sorbitol while commensal E. coli are sorbitol-positive
- Immunoassay for shiga-like toxin
- do strain typing with PCR or DNA probe analysis
how can you prevent E. coli spread and infection?
- Hygiene
- Hay fed cattle are less likely to harbor E. coli than grain fed cattle due to higher stomach pH
how are STEC & EHEC (Shiga toxin and Enterohemorrhagic) diagnosed?
- PCR/immunoassay for shiga toxin
- Nucleic acid detection of virulence genes
- EHEC-sorbitol fermentation
how is ETEC (Enterotoxigenic) diagnosed?
- Nucleic acid detection of virulence genes
how is EPEC (Enteropathogenic) diagnosed?
- Nucleic acid detection of virulence genes or tissue culture assay for aggregative adherence
how is EAEC (Enteroaggregative) diagnosed?
Nucleic acid detection of virulence genes or tissue culture assay for aggregative adherence
how is EIEC (Enteroinvasive) diagnosed?
Nucleic acid detection of virulence genes
