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Growth Inhibition of an Opportunistic Yeast Pathogen Trichosporon asahii by Staphylococcus epidermidis
Reiko Ikeda1, Yuki Ogasawara2, Kazuhiko Takatori3
1Department of Microbial Science and Host Defense, Meiji Pharmaceutical University.
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.
Insights
Live Staphylococcus epidermidis bacteria inhibit the growth of the fungal pathogen Trichosporon asahii. This inhibition is due to lactic acid, a metabolite produced by S. epidermidis, highlighting microbial interactions in infections.
Area of Science:
- Microbiology
- Mycology
- Bacterial-Fungal Interactions
Background:
- Co-culture experiments revealed that Staphylococcus epidermidis inhibits the growth of the fungal pathogen Trichosporon asahii.
- This suggests that S. epidermidis produces soluble substances that are active against T. asahii.
Purpose of the Study:
- To identify the specific molecule produced by S. epidermidis responsible for inhibiting T. asahii growth.
- To understand the role of bacterial metabolites in host-pathogen interactions and opportunistic fungal infections.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy (¹H and ¹³C) was used for structural elucidation.
- High-resolution mass spectrometry (HR-negative-FAB-MS) aided in molecule identification.
- Growth inhibition assays were performed using commercially available L-lactic acid and D-lactic acid.
Main Results:
- The active molecule inhibiting T. asahii was isolated and identified as lactic acid.
- Both L-lactic acid and D-lactic acid demonstrated significant inhibition of T. asahii growth.
- This confirms lactic acid as the key metabolite mediating the observed bacterial antagonism.
Conclusions:
- Bacterial metabolites play a crucial role in the complex interactions between bacteria and pathogenic fungi.
- The use of antibacterial agents may disrupt beneficial microbial communities, potentially leading to opportunistic infections like trichosporonosis.
- Understanding these microbial dynamics is vital for managing opportunistic fungal infections.
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