BSCI 424 — PATHOGENIC MICROBIOLOGY — Fall 2000


Escherichia coli Summary

Morphology & Physiology:

  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

Taxonomy:

  Family Enterobacteriaceae

  Escherichia coli

  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

Clinical Syndromes:

  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

Epidemiology:

  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)

Pathogenesis & Immunity:

  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

Laboratory Identification:

  Mere isolation of E. coli from specimens is not definitive diagnosis

Treatment, Prevention & Control:

  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
AFFECTED

CLINICAL
SYNDROME

ADHESINS
EXOTOXINS
PATHOGENESIS
Opportunistic
E. coli

Various
sites

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
Enteroinvasive
E. coli (EIEC)
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

   Go to Pathogen List

 

 

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Designed & Maintained by David M. Rollins
Copyright © 2000, D.M. Rollins and S.W. Joseph
Revised: August 2000
URL: http://life.umd.edu/classroom/bsci424