Gram-negative bacilli (see WebLinked image)
Cultural Characteristics: grow as fermenting colonies, some beta-hemolysis upon initial isolation; motile, non-pigmented
Antigenic Structure: O, K, H antigens typed serologically as an epidemiologic tool
Family Enterobacteriaceae
- Opportunistic Escherichia coli
- ETEC = enterotoxigenic E. coli
- EIEC = enteroinvasive E. coli
- EPEC = enteropathogenic E. coli
- EHEC = enterohemorrhagic E. coli
- EaggEC = enteroaggregative E. coli
- UPEC = uropathogenic E. coli
85% of urinary tract infections
50% of primary nosocomial pneumonia in some hospitals
Major cause of neonatal meningitis with up to 80% mortality
Gastroenteritis (see above and Summary Table below for specific syndromes and virulence factors associated with specific strains)
Wound infections
Peritonitis: sepsis
Most predominant organism of the large intestine
Ordinarily non-pathogenic but may be opportunistic or true pathogens (see above and Summary Table below for specific syndromes and virulence factors associated with specific strains)
Fimbriae (formerly pili): important for colonization of host tissues
Some strains have adhesins and exotoxins (enterotoxins) as virulence factors and are true pathogens (see above and Summary Table below for specific syndromes and virulence factors associated with specific strains)
Other invasive factors
Mere isolation of E. coli from specimens is not definitive diagnosis
Diarrhea: fluid and electrolyte replacement; trimethoprim-sulfamethoxazole prophylactically
Other Conditions: treatment varies depending upon site of infection and antibiogram of isolate
Summary of Clinical Syndromes and Virulence Factors of Escherichia coli |
|||||
SITE |
CLINICAL |
ADHESINS
|
EXOTOXINS
|
PATHOGENESIS
|
|
Opportunistic
E. coli |
Various |
See above and Enterobacteriaceae |
??
|
??
|
Urinary tract infections; Primary nosocomial pneumonia; neonatal meningitis; Wound infections; Peritonitis; septicemia |
Enterotoxigenic
E. coli (ETEC) |
Small intestine
|
Traveller's diarrhea |
Type 1 pili; Colonization factor antigens (CFA/I; CFA/II)
|
Heat stable toxins (STa; STb); Heat labile toxins (LT-I;
LT-II)
|
Hypersecretion of fluids and electrolytes stimulated by plasmid-mediated enterotoxins |
|
Large intestine
|
Shigellosis-like disease in developing countries |
??
|
??
|
Plasmid-mediated invasion and destruction of enterocytes |
Enteropathogenic
E. coli (EPEC) |
Small intestine
|
Infant diarrhea |
Bundle-forming pili (Bfp); Intimin
|
??
|
Plasmid-mediated adherence and destruction of enterocytes |
Enterohemorrhagic E. coli (EHEC)
|
Large intestine
|
Hemmorrhagic colitis possible leading to hemolytic uremic syndrome (HUS) |
Intimin
|
Shiga-like toxins (SLT-I; SLT-II)
|
Inhibition of protein synthesis by lysogenic bacteriophage-encoded cytotoxic enterotoxins |
Enteroaggregative E. coli (EaggEC)
|
Small intestine
|
Infant diarrhea in developing countries |
GVVPQ fimbriae
|
Enteroaggregative heat stable toxin
|
Inhibition of fluid absorption by plasmid-mediated aggregative adherence |
Uropathogenic
E. coli (UPEC) |
Urinary tract
|
Urinary tract infections |
P pili; Afimbrial adhesins (AFA-I; AFA-III); Dr adhesin
|
HlyA (hemolysin)
|
Adherence to specific receptors on epithelial cells of the bladder and upper urinary tract with HlyA cell lysis leading to cytokine release and inflammatory responses |
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