Antifungal potential of entomopathogenic bacteria, Photorhabdus, and Xenorhabdus (Morganellaceae) against pathogenic fungi

Entomopathogenic bacteria (EPB) are natural pathogens of insects being utilized as biological control agents for insect pests worldwide. In addition to their pathogenicity against insects, they are known to inhibit the growth of several microbes. In this study, EPB of the genus, Photorhabdus and Xenorhabdus, were investigated for their pathogenicity against Fusarium solani (CCK3A1), Fusarium keratoplasticum (ATCC 36031), Candida albicans (ATCC 2091), and Aspergillus fumigatus (ATCC 204305). The antagonistic effect of cell suspension was analyzed by calculating percent inhibition from the co-cultured plate of bacteria and fungus within 192 hours of incubation at 25°C where the highest percent inhibition was observed with X. vietnamensis (RF) against A. fumigatus (ATCC 204305). Moreover, the activity of ethyl acetate extract of bacterial metabolites against pathogenic fungi was analyzed using the disk diffusion method where Photorhabdus hindustanensis (TS) isolates exhibited the highest inhibition against A. fumigatus (ATCC 204305). The components of ethyl acetate extract were analyzed using gas chromatography-mass spectrometry in which Pyrrolo [1,2-a] pyrazine-1,4-dione hexahydro-3-(phenylmethyl), benzeneacetic acid, and n-Hexadecanoic acid were found to be the most abundant compounds. This study provides information regarding the potential of Photorhabdus and Xenorhabdus, including their secondary metabolites against several pathogenic fungi. It further provides insights to overcome the current global drug resistance crisis among several pathogenic fungi, as well as new reference data for the future development and application of antifungal agents.