ABSTRACT
In the co-culture of Staphylococcus epidermidis and Trichosporon asahii, a fungal pathogen, it was observed that live S. epidermidis inhibited the growth of T. asahii. Soluble active anti-T. asahii substances were speculated to be produced by S. epidermidis in culture medium. Using 1H- and 13C-NMR spectra and electron ionization-high resolution mass spectrometry (HR-negative-FAB-MS), we separated the active molecule and identified it as lactic acid. Commercially available L-lactic acid and D-lactic acid inhibited the growth of T. asahii. These results show that metabolites from bacterial populations are involved in the interactions of pathogenic fungi. The use of antibacterial agents to treat primary diseases could lead to the disruption of normal microbial communities and could cause opportunistic infections such as trichosporonosis.