Proteus species


Enterobacteriaceae  (Gram Negative Bacilli)  
>Citrobacter species:
     1] Citrobacter koseri
     2] Citrobacter freundii
>Enterobacter species
     1] Enterobacter cloacae,
     2] Enterobacter aerogenes)
>Escherichia coli
>Klebsiella species:
     1] Klebsiella ozaenae
     2] Klebsiella pneumoniae
     3] Klebsiella rhinoscleromatis
>Morganella species 
     1] (Morganella morganii)
>Proteus species: led
     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


  • Gram-negative, oxidase-negative,  catalase- and nitrate-positive, and urease positive.
  • Widely distributed in nature as saprophytes, being found in decomposing animal matter, in sewage, in manure soil, and in human and animal feces.
  • They are opportunistic pathogens, commonly responsible for urinary and septic infections, often nosocomial. Three species – P. vulgaris, P. mirabilis, and P. penneri –  are opportunistic human pathogens.
  • On the species level, indole is considered reliable, as it is positive for Proteus vulgaris but negative for Proteus mirabilis.
  • Most strains produce a powerful urease enzyme, which rapidly hydrolyzes urea to ammonia and carbon monoxide.


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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.  

Proteus mirabilis:

  1. Ceftin (cefuroxime oral) 250-500mg orally twice daily
  2. Augmentin 875/125 mg orally twice daily
  3. Ciprofloxacin 500-750 mg orally q12h or 400mg IV q12h
  4. Levofloxacin 500mg – 750 mg IV/PO once daily
  5. Ceftriaxone 1-2 grams IV q24h 

Proteus vulgaris:

  1. Ciprofloxacin 500-750 mg orally q12h or 400mg IV q12h
  2. Levofloxacin 500mg – 750 mg IV/PO once daily
  3. Ceftriaxone 1-2 grams IV q24h 
  4. Cefepime 1-2 grams IV every 8-12 hours
  5. Imipenem 500mg IV every 6 hours [Range: 250-1000 mg q6-8h]


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