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Bacteroides melaninogenicus / Prevotella species


Anaerobic Gram-Negative Bacilli
>Bacteroides fragilis (most important clinically)
    [Other Bacteroides species  – less common clinically:  (B. acidifaciens, B. gracilis,
         B. oris, B. ovatus,  B. pyogenes , B. stercoris, B. vulgatus)]
>Bacteroides melaninogenicus (reclassified and split into Prevotella melaninogenica
     and Prevotella intermedia.)led
>Fusobacterium necrophorum
>Porphyromonas gingivalis

Bacteroides melaninogenicus

  • Bacteroides melaninogenicus was later changed to Prevotela melaninogenica.
  • anaerobic gram negative rod, named for its black colonies, and black pigment.
  • Normal flora of the upper respiratory tract.
  • It is an important human pathogen in various anaerobic infections, often mixed with other aerobic and anaerobic bacteria.

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Prevotella species

  • normal human oral and vaginal flora and are the predominant anaerobic, Gram-negative bacilli recovered from anaerobic infections of the respiratory tract (include aspiration pneumonia, lung abscesses, and chronic otitis media and sinusitis).
  • Prevotella species have been recovered also from abscesses and burns around the oral cavity, human bites, paronychia, urinary tract infection, brain abscesses, osteomyelitis and bacteremia associated with upper respiratory tract infections.
  • Play a major role in the pathogenesis of periodontal disease and periodontal abscesses. The prevalence of Prevotela melaninogenics is high in the dental plaque of persons with Down syndrome.

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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.

  1. Metronidazole 500mg IV/PO every 6 hours
  2. Augmentin 875/125 mg orally twice daily
  3. Piperacillin-tazobactam (Zosyn ®)  3.375 to 4.5  grams IV q6h
  4. Imipenem 500mg IV every 6 hours [Range: 250-1000 mg q6-8h]
  5. Meropenem 0.5 – 1 gram IV q8h 
  6. Doripenem 500 mg IV q8h
  7. Chloramphenicol 50-100 mg/kg/day IV in divided doses every 6 hours (Maximum daily dose is 4 grams e.g. 1 gram q6h)

Bacteroides melaninogenicus