Antifungal activity of marine‐derived actinomycetes against Talaromyces marneffei

This study aimed to isolate actinomycetes from marine environments and examine their antifungal activity against Talaromyces marneffei both in vitro and in vivo. Nineteen out of 101 actinomycete extracts were active and further determined for their minimum inhibitory concentrations (MIC). Three extracts of AMA50 that isolated from sediment showed strong antifungal activity against T. marneffei yeast (MICs ≤0·03–0·25 µg ml−1) and mould (MICs 0·5–16 µg ml−1) forms. The hexane extract from the cells of AMA50 (AMA50CH) exhibited the best activity against both the forms (MIC ≤ 1 µg ml−1). Three extracts from AMA50 killed the melanized yeast cells at 0·5 µg ml−1. The AMA50CH was further tested for protective effects in Caenorhabditis elegans model. At concentrations of 1–8 µg ml−1, the AMA50CH prolonged survival of T. marneffei‐infected C. elegans with a 60–70% survival rate. The composition of AMA50CH was determined by gas chromatography‐mass spectrometry. The major components were n‐hexadecanoic acid, tetradecanoic acid and pentadecanoic acid. Sequencing analysis revealed that isolate AMA50 belonged to the genus Streptomyces. The AMA50CH from Streptomyces sp. AMA50 was the most effective extract against T. marneffei. Talaromyces marneffei is one of the most important thermally dimorphic pathogenic fungi. These results indicated the potency of marine‐derived actinomycete extracts against T. marneffei both in vitro and in vivo.