Antibacterial activity of symbiotic bacterial isolates of Entomopathogenic Nematodes against Human pathogens

Five isolates of local symbiotic bacteria SEC-1, SEC-7, SEC-8, SEC-9 and SEC-11 with two standard cultures Photorhabdus luminiscens and Xenorhabdus nematophilus isolated from the entomopathogenic nematode cultures Heterorhabditis indica and Steinernema carpocapsae were evaluated for the antimicrobial activity against four human pathogens. The cell free extracts of symbiotic bacterial isolates showed significant inhibition against Escherichia coli and Staphylococcus aureus, but against Klebsiella sp. and Pseudomonas aeroginosa, results were not significant. Among the isolates SEC-1 (96.25mm²) was superior over other isolates for E. coli, SEC-8 (229.63mm²) against S. aureus while SEC-9 (76.41mm²) exhibited a significant antibiotic activity against Pseudomonas aeroginosa, while SEC-1 (33.19mm²), Xenorhabdus (22mm²) and SEC7 (10.21mm²) were on par with each other. Photorhabdus (10.21mm²) was the only isolate which showed inhibitory effect against Klebsiella spp. but the other isolates did not show any antibiosis. The results of the assessed data of the antimicrobial activity of the symbiotic bacteria revealed that the isolates SEC-1, SEC-7, SEC-8, SEC-9, SEC-11 were most effective. These isolates could be explored for potential specific antibacterial compound which could be used in pharmaceutical therapeutic action.