Microbiology & infectious diseases
Gram negative bacteria
E. coli
Author: Christopher S. Hale, M.D.
Last author update: 1 September 2013
Last staff update: 5 October 2020
Copyright: 2002-2025, PathologyOutlines.com, Inc.
PubMed Search: Escherichia coli [title]
Table of Contents
Definition / general | Terminology | Etiology | Laboratory | Treatment | Gross description | Molecular / cytogenetics description | Differential diagnosis | Additional referencesCite this page: Hale C. E. coli. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/microbiologyescherichiacoli.html. Accessed January 21st, 2025.
Definition / general
- Gram stain: negative
- Morphology: bacilli
- Facultative anaerobe
- Normal component of bowel microflora
- Glucose fermenting, oxidase negative, nitrate reducer
- Motile
Terminology
- Named after Theodor Escherich (Clin Infect Dis 2007;45:1025)
- Serotyping based on O antigen (somatic) and H antigen (flagellar)
Etiology
- Urinary tract infections
- Bacteremia
- Meningitis
- O157 : H7 strain associated with Hemolytic Uremic Syndrome (TTP / HUS) from contaminated beef
- Diarrhea-producing strains:
- Shiga Toxin producing E. coli (STEC)
- Enterohemorrhagic E. coli (EHEC)
- Enterotoxin producing E. coli (EPEC)
- Enteroinvasive E. coli (EIEC)
- Enteropathogenic E. coli (EPEC)
- Enteroaggregative E. coli (EAEC)
Laboratory
- Culture conditions:
- 37, MacConkey agar (selective for gram negative bacteria)
- Gram negative
- IMViC (Indole, Methyl Red, Voges-Proskauer, Citrate) pattern: (+), (+), (-), (-)
- Non - O157 strains ferment lactose on MacConkey agar, O157 serotypes lose ability to ferment sorbitol
- No selective culture medium exists for non - O157 strains; test for Shiga toxin using EIA (enzyme immunoassay) or use chromogenic agar
- Acid/Acid, gas - producer pattern on Triple Sugar Iron (TSI) slant test
Treatment
- Urinary tract infections traditionally treated with:
- Fluoroquinolones
- Cephalosporins
- Trimethoprimsulfamethoxazole
- Resistance to fluoroquinolones and cephalosporins emerging in extraintestinal E. coli (Expert Rev Anti Infect Ther 2012;10:1165)
- Bacteremia often treated with empirical combination antibiotic regimen directed against gram negative bacteria (i.e., B - lactam plus aminoglycoside or fluoroquinolone) (Antimicrob Agents Chemother 2010;54:1742)
- Plasmid - mediated AmpC B - lactamases (e.g., CMY), extended - spectrum B - lactamases (e.g., CTX - M), and carbapenemases seen increasingly (Front Microbiol 2012;3:9)
Gross description
- White
Molecular / cytogenetics description
- Multiplex PCR for detection of pathogenic E. coli becoming available (Front Cell Infect Microbiol 2012;2:8)
Differential diagnosis
- Other members of Enterobacteriaceae (Salmonella, Shigella, etc.)
