Antibacterial activity of entomopathogenic fungi isolated from Apis dorsata (Giant Honeybee) and Vespa affinis (Lesser Banded Hornet) in Sri Lanka

Abstract

The global rise in bacterial drug resistance highlights the urgent need for novel antibiotics. Entomopathogenic fungi (EPF) represent an underexplored yet promising source of antimicrobial secondary metabolites. This study reports, for the first time, the isolation of EPF from Apis dorsata and Vespa affinis in Sri Lanka and the evaluation of their crude extracts for antibacterial activity. EPF were isolated from surface-sterilized insect cadavers, cultured on PDA, and extracted with ethyl acetate. Molecular methods were used for fungal identification. Antibacterial activity of crude extracts was assessed by agar disc diffusion and bioautography against Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Pseudomonas aeruginosa, using methanol and gentamycin as negative and positive controls. Nine fungal isolates from A. dorsata and eight from V. affinis were obtained. The crude extract of Talaromyces aculeatus (BB1) from A. dorsata showed strong activity against E. coli (13 mm inhibition zone at 400 μg/disc; P > 0.05 vs. gentamycin) and additional activity against S. aureus in bioautography. Aspergillus nomius (VA7) inhibited B. cereus, while Aspergillus niger (BB10) was active against S. aureus. These findings reveal that EPF from A. dorsata and V. affinis are promising sources of novel antibacterial agents, with, particularly T. aculeatus.