Chiang Mai Journal of Science

     A total of sixteen antimicrobial-producing fungal isolates were isolated from forest soil collected from Suranaree University of Technology (SUT), Thailand. These fungal isolates exhibited antimicrobial activity against test pathogenic Gram-positive bacteria (methicillin-resistant Staphylococcus aureus (MRSA), S. aureus, S. epidermidis, Bacillus subtilis, and B. cereus), Gram-negative bacteria (Escherichia coli, Enterobacter aerogenes, Salmonella typhimurium, and Proteus mirabilis), and yeasts (Candida albicans, C. tropicalis, and Saccharomyces cerevisiae). The fungal isolates that exhibited the highest antimicrobial activity against MRSA, S. aureus, S. epidermidis, B. subtilis, B. cereus, E. coli, En. aerogenes, Sal. typhimurium, P. mirabilis, C. albicans and C. tropicalis are PKF125, PKF60, PKF125, PKF6, PKF127, PKF104, PKF152, PKF152, PKF152, PKF105 and PKF105, respectively. The highest antifungal activity toward Sac. cerevisiae was observed from PKF77 and PKF105. An initial molecular classification of fungal strains was conducted by sequencing the internal transcribed spacer (ITS) region. The ITS region of fungal isolates were analyzed by BLAST search and phylogenetic analysis. The BLAST search revealed that 16 fungal isolates were members of the genus Aspergillus (9 isolates), Penicillium (3 isolates), Clonostachys (2 isolates) and Talaromyces (2 isolates). The obtained fungal isolates in the genus Aspergillus were separated into three sections including Flavipedes (PKF116, PKF145, and PKF105), Nigri (PKF161), and Flavi (PKF59, PKF38, PKF6, PKF60, and PKF61). On the otherhand, isolates PKF121, PKF125,and PKF127 were placed in Penicillium section Citrina. Isolate PKF152 and PKF124 were assigned toTalaromyces section Talaromyces and Islandici, respectively. Isolate PKF77 and PKF104 were deemed as Clonostachys rogersoniana. The current study suggests that unexplored forest soil represents a rich reservoir for the search of new antimicrobial compounds. Fungal isolates in this study exhibited the ability to inhibit MRSA, providing insights into pharmaceutical targeting against drug-resistant microorganisms