• See Also
  1. Bacteroidaceae
  2. Gram Negative Bacteria
  • Pathophysiology
  1. Bacteroides fragilis are obligate anaerobic Gram Negative Rods in the Bacteroidaceae family
  2. Bacteroides fragilis has a capsule
  3. Bacteroides fragilis secretes an Enterotoxin (BFT)
    1. However, does not contain Lipid A or Endotoxin (unlike most other Gram Negative Bacteria)
  4. Bacteroides fragilis is a normal colonizer of the Gastrointestinal Tract (25% of intestinal flora)
    1. Low virulence unless intestinal wall is perforated
    2. May also be associated with Inflammatory Bowel Disease flares
  • Associated Conditions
  1. Bacteroides fragilis rarely colonizes the mouth (uncommon cause of Aspiration Pneumonia)
  2. Intraabdominal anaerobic Bacterial Infections and abscesses
    1. Bacteroides fragilis is found in most intraabdominal anaerobic infections
    2. Among the most commonly isolated Bacteria in anaerobic bacteremia
    3. Occurs with Bowel perforation, Mesenteric Ischemia, Pelvic Inflammatory Disease, Septic Abortion
  3. Wound Infections
    1. Diabetic Foot Infections or chronic Pressure Ulcers
    2. Necrotizing Fasciitis
  • Management
  1. Source control with abscess drainage
  2. Antibiotics with highest efficacy against Bacteroides fragilis (lower resistance rates)
    1. Piperacillin Tazobactam (zosyn)
    2. Meropenem
    3. Metronidazole
  3. Antibiotics with high Bacteroides fragilis resistance rates (low susceptibility)
    1. Cefoxitin
    2. Moxifloxacin
    3. Clindamycin
  • Prognosis
  1. Bacteroides fragilis bacteremia is associated with mortality as high as 30%
  • Resources
  1. lsaghir (2023) Bacteroides fragilis, StatPearls, Treasure Island, Fl
    1. https://www.ncbi.nlm.nih.gov/books/NBK553032/
  • References
  1. Patrick (2022) Microbiology 168(4) +PMID: 35404220 [PubMed]