Mobiluncus species and other anaerobic bacteria in non-puerperal breast abscesses

Samples of 109 breast masses were cultured aerobically and anaerobically for Mobiluncus spp. using selective and non-selective media. Two of the 103 evaluable samples were sterile and 57 (55%) yielded facultative bacteria only. The remaining 44 (43%) contained anaerobic growth alone or mixed infections. Seven (16%) of the 44 samples with anaerobes, six from women and one from a man, yielded Mobiluncus spp. Six were identified as Mobiluncus curtisii and one as Mobiluncus mulieris. There were two types of breast abscesses: one with Staphylococcus aureus predominating and one with anaerobes predominating. Most of the anaerobes belonged to the normal vaginal flora, but some were members of the normal oral flora. These results support the hypothesis that breast infections with these anaerobes result from sexual activities.