Escherichia coli


Enterobacteriaceae  (Gram Negative Bacilli)  
>Citrobacter species:
     1] Citrobacter koseri
     2] Citrobacter freundii
>Enterobacter species
     1] Enterobacter cloacae,
     2] Enterobacter aerogenes)
>Escherichia coli Led
>Klebsiella species:
     1] Klebsiella ozaenae
     2] Klebsiella pneumoniae
     3] Klebsiella rhinoscleromatis
>Morganella species 
     1] (Morganella morganii)
>Proteus species:
     1] Proteus mirabilis
     2] Proteus vulgaris
>Providencia species:
     1] Providencia_rettgeri
     2] Providencia stuartii
>Salmonella species:
     1] Salmonella enteritidis
     2] Salmonella typhi
     3] Other
>Serratia marcescens
>Shigella species:  
     1] Shigella dysenteriae (serogroup A)
     2] Shigella flexneri
     3] Shigella boydii
     4] Shigella sonnei
     5] Other

Escherichia coli:

  • Gram-negative, facultative anaerobic, non-sporulating, rod-shaped bacterium. Strains that possess flagella are motile.
  •  E. coli and related bacteria constitute about 0.1% of gut flora.  Fecal-oral transmission is the major route through which pathogenic strains of the bacterium cause disease.
  • Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls due to food contamination.
  • The harmless strains are part of the normal flora of the gut, and can benefit their hosts by producing vitamin K2, and by preventing the establishment of pathogenic bacteria within the intestine.
  • Virulent strains of E. coli can cause gastroenteritis, urinary tract infections, and neonatal meningitis. In rarer cases, virulent strains are also responsible for hemolytic-uremic syndrome, peritonitis, mastitis, septicemia and Gram-negative pneumonia.
  • UPEC (uropathogenic E. coli) is one of the main causes of urinary tract infections. It is part of the normal flora in the gut and can be introduced many ways.
  • Certain strains of E. coli are a major cause of foodborne illness.

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Important considerations:  The choice of an agent should be based on local antimicrobial sensitivities, site of infection, cost, and comorbid conditions.   Generally, the most common agents/regimens are listed first. Listed dosages may need to be adjusted for renal dysfunction.  

  1. UTI (uncomplicated):
    • Nitrofurantoin:  50-100mg orally q6h.  Macrobid® 100mg orally bid.  Renal: use is contraindicated for CrCl <60 ml/min.
    • Fosfomycin 3 grams in 3-4 oz of water orally x 1.
    • Ciprofloxacin 250 mg orally q12h
  2. Gastroenteritis:
    • Ciprofloxacin 500 mg orally q12h
    • Rifaximin 200mg orally three times daily x 3 days.
  3. Extended spectrum beta-lactamase (ESBL) producing strains
    • Imipenem 500mg IV every 6 hours [Range: 250-1000 mg q6-8h]
    • Meropenem 0.5 – 1 gram IV q8h
  4. Carbapenemase producing strains – Carbapenem-resistant enterobacteriaceae (CRE)
    • Colistimethate (colistin base): 2.5 – 5mg/kg/day in 2-4 divided doses. Max 5 mg/kg/day   PLUS   [ Meropenem 1 gram IV q8h  OR  Imipenem 500mg IV every 6 hours [Range: 250-1000 mg q6-8h]

Escherichia coli