Antibacterial activity of Xenorhabdus and Photorhabdus isolated from entomopathogenic nematodes against antibiotic-resistant bacteria

Abstract

Xenorhabdus and Photorhabdus, symbiotically associated with entomopathogenic nematodes (EPNs), produce a range of antimicrobial compounds. The objective of this study is to identify Xenorhabdus and Photorhabdus and their EPNs hosts, which were isolated from soil samples from Saraburi province, and study their antibacterial activity against 15 strains of drug-resistant bacteria. Fourteen isolates (6.1%), consisting of six Xenorhabdus isolates and eight Photorhabdus isolates, were obtained from 230 soil samples. Based on the BLASTN search incorporating the phylogenetic analysis of a partial recA gene, all six isolates of Xenorhabdus were found to be identical and closely related to X. stockiae. Five isolates of Photorhabdus were found to be identical and closely related to P. luminescens subsp. akhurstii. Two isolates of Photorhabdus were found to be identical and closely related to P. luminescens subsp. hainanensis. The remaining isolate of Photorhabdus was found to be identical to P. asymbiotica subsp. australis. The bacterial extracts from P. luminescens subsp. akhurstii showed strong inhibition the growth of S. aureus strain PB36 (MSRA) by disk diffusion, minimal inhibitory concentration, and minimal bactericidal concentration assay. The combination between each extract from Xenorhabdus/Photorhabdus and oxacillin or vancomycin against S. aureus strain PB36 (MRSA) exhibited no interaction on checkerboard assay. Moreover, killing curve assay of P. luminescens subsp. akhurstii extracts against S. aureus strain PB36 exhibited a steady reduction of 10 5 CFU/ml to 10 3 CFU/ml within 30 min. This study demonstrates that Xenorhabdus and Photorhabdus, showed antibacterial activity. This finding may be useful for further research on antibiotic production.

A study on Xenorhabdus and Photorhabdus isolates from Northeastern Thailand: Identification, antibacterial activity, and association with entomopathogenic nematode hosts

“…This suggests that global prevalence of EPNs is variable. Distribution of Steinernema and Heterorhabditis has been reported from several ecological niches in USA, Australia, Europe, and Asia, including Thailand [ 8 , 15 – 18 , 24 , 40 , 41 ]. Biotic and abiotic characteristics influence the distribution of the EPNs; however, in our study, soil temperature, moisture, and pH of the soil samples with and without EPNs were not significantly different.…”

“…akhurstii (bSBR11.1_TH) extract from Saraburi province could inhibit up to 10 antibiotic-resistant bacterial strains, and all Photorhabdus isolates showed the potential to inhibit the growth of S . aureus strain PB36 (MRSA) [ 41 ]. P .…”

Photorhabdus spp.: An Overview of the Beneficial Aspects of Mutualistic Bacteria of Insecticidal Nematodes

“…Thus, these toxins show bacterial strain-specific variations concerning toxicity to their insect hosts [ 9 , 80 ]. Different features regarding the detailed structure, mode of action, and putative function of the Tcs as ‘polymorphic’ toxins in the process of infection, have been discussed [ 81 , 82 ], but the modes of action of some recently detected metabolic compounds of Photorhabdus bacteria still need to be grasped, to enable their perfect use in the management of agricultural pathogens and insect pests [ 8 , 9 ]. Photorhabdus bacteria can also suppress important endoparasitic nematode species within plant roots, via their toxins and antibiotic compounds [ 5 ].…”

“…These bacteria can reduce the chemical inputs used for plant protection, and stabilize ecological changes [ 4 ]. Conceivably, entomopathogenic bacterial species of the genus Photorhabdus (Enterobacteriales: Morganellaceae) may be a favorable alternative for expanding the biocontrol of many plant pests and pathogens, via their secretion of various arrays comprising effective bioactive metabolites [ 2 , 5 , 6 , 7 , 8 , 9 ]. This concept is based on a huge number of Photorhabdus genes that encode for producing relevant compounds, e.g., enzymes, toxins, antibiotics, and bacteriocins.…”

“…They are found in the form of pathogenicity islands on the bacterial chromosomes representing different groups, e.g., the group of toxins is assorted to four prime groups. Additionally, discoveries of novel species of Photorhabdus , with presumed additional genes encoding for beneficial traits, are being discovered, and novel genes in the Photorhabdus species that are already described are ongoing, and can further be exploited [ 1 , 8 , 9 , 10 , 11 ]. The goal of this paper is to provide an overview on the pros and cons of Photorhabdus spp.…”