Peptococcus magnus: a significant human pathogen.

Peptococcus magnus was recovered from 10% of anaerobic cultures collected from suspected clinical infections over a 3.5-year period. It was the commonest species of anaerobic gram-positive cocci isolated (30%). To evaluate the clinical significance of this organism, we retrospectively reviewed the charts of 222 patients from whom P. magnus was isolated. Twenty-five patients had no evidence of infection, 151 had mixed infections, and 32 had infections from which only P. magnus was isolated (pure cultures). Mixed infections involved the following sites: bone and joint (32 cases), soft tissue (57 cases), foot ulcers (29 cases), abdominal cavity (16 cases), and miscellaneous (17 cases). The average number of organisms was four (2.5 facultatives and 1.5 anaerobes). Eighteen patients with pure cultures of P. magnus had bone or joint infections, and foreign bodies were present in 15 of these. Other pure cultures of P magnus infections included 12 soft tissue, one vascular graft, and one infected sternotomy with persistent bacteremia. Pure culture infections were usually chronic, and serious sequelae often resulted. Peptococcus magnus is frequently isolated from significant infections and seems particularly pathogenic in infections of bones and joints or in association with the presence of foreign bodies, or both.