Bacteroides fragilis Group

Valeria Fabre, M.D.


  • Small, pleomorphic Gram-negative anaerobic bacillus.
    • Of all species, B. fragilis causes most human Bacteroides infections.
  • Other commonly encountered members of the B. fragilis group [BFG] include Bacteroides, Parabacteroides and Phocaeicola species: speciation has been aided by the employment of MALDI-TOF[3].
    • Bacteroides distasonis, Bacteroides merdae, and Bacteroides goldsteinii have been reclassified to a new genus, Parabacteroides.
      • Tannerellaceae” family has been proposed as a new name.
        • Therefore, the revised taxonomy are Parabacteroides distasonis, P. merdae, and P. goldsteinii
    • Bacteroides ovatus
    • Bacteroides thetaiotaomicron
    • Bacteroides uniformis
    • Bacteroides vulgatus
  • Quickly grown relative to other anaerobes.
  • Bacteroides spp. colonize all human colons, representing ~ 25% of human intestinal microbiota.
  • Organisms are possibly important in the gut for immune modulation.

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Last updated: January 11, 2023