Peptostreptococcus spp. (and Finegoldia magna)


  • Anaerobic Gram-positive cocci: part of the normal flora of the mouth, GI and GU tracts, and skin.
  • A heterogeneous group of "anaerobic streptococci" is now classified into five groups, and changes in the taxonomy can be confusing.
    • Peptoniphilus lacrimalis, P. ivorii, Anaerococcus octavius, Peptostreptococcus anaerobius and Micromonas micros.
    • Others were reclassified. For example, Finegoldia magna is the former Peptosteptococcus magnus.
  • Small cocci may be seen on Gram stain in short chains and pairs.
    • GPC may appear identical to aerobic streptococci (chains) or staphylococci (clusters) [Fig].
    • Non-spore forming
  • Peptostreptococcus (which includes the former Peptococcus) accounts for nearly all anaerobic GPC except Finegoldia magna.
  • Most common and important: Finegoldia magna, P. asaccharolyticus.
    • Less common: P. micros, P. anaerobius.
  • Note: Microaerophilic streptococci, such as Streptococcus intermedius Group, are pathogenic and often important in mixed infections.
    • They are not Peptidostreptococci and are not sensitive to metronidazole.

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Last updated: June 9, 2024