Official website of the Johns Hopkins Antibiotic (ABX), HIV, Diabetes, and Psychiatry Guides, powered by Unbound Medicine. Johns Hopkins Guide App for iOS, iPhone, iPad, and Android included. Explore these free sample topics:
-- The first section of this topic is shown below --
- Gram-negative (GN) rod, E. coli member of Enterobacteriaceae: human strains may be: (1) commensal bowel flora, (2) intestinal pathogenic (enteric/diarrheogenic), (3) extraintestinal pathogenic.
- Predominant GN in composition of normal human colonic flora.
- E. coli easy to grow from sterile specimens.
- Stool cx: only if chronic diarrhea (need reference lab to ID) or suspect O157:H7 (cx all bloody diarrhea) use sorbitol-MacConkey agar or perform Shiga toxin EIA.
- ~ 90% strains ferment lactose; some diarrheogenic E. coli strains, including many of the EIEC strains, typically lactose negative. Indole test 99% (+).
- Major resistance concerns:
- Plasmid-mediated AmpC β-lactamases (e.g., CMY)
- Extended-spectrum β-lactamases (e.g., CTX-M)
- Now worldwide concern in community-acquired UTIs and also bloodstream infections
- In some Asian countries rates of ESBL E. coli have been reported as high as 55-79%.
- Rates are lower in North America but rising.
- Carbapenemases (e.g., New Delhi metallo-β-lactamase, Klebsiella pneumonaie carbapenemase and OXA-48)