Peptococcus magnus: A Significant Human Pathogen

Abstract

P. magnus was recovered from 10% of anaerobic cultures collected from suspected clinical infections over 3.5 yr. It was the commonest species of anaerobic gram-positive cocci isolated (30%). The clinical significance of this organism was evaluated by reviewing the charts of 222 patients from whom P. magnus was isolated; 25 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 4 (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, 1 vascular graft and 1 infected sternotomy with persistent bacteremia. Pure culture infections were usually chronic and serious sequelae often resulted. P. magnus is frequently isolated from significant infections and seems particularly pathogenic in infections of bones and joints and/or in association with the presence of foreign bodies.