Safety attributes of Pseudomonas sp. P26, an environmental microorganism with potential application in contaminated environments

Abstract

Currently, the selection of non-pathogenic microorganisms that lack clinically relevant antimicrobial resistance iscrucial to bioaugmentation strategies. Pseudomonas sp. P26 (P26) is an environmental bacterium of interest dueto its ability to remove aromatic compounds from petroleum, but its safety characteristics are still unknown. Thestudy aimed to: a) determine P26 sensitivity to antimicrobials, b) investigate the presence of quinolone andβ-lactam resistance genes, c) determine the presence of virulence factors, and d) evaluate the effect of P26 on theviability of Galleria mellonella (an invertebrate animal model). P26 antimicrobial sensitivity was determined invitro using the Kirby-Bauer agar diffusion method and the VITEK 2 automated system (BioMerieux®). PolymeraseChain Reaction was employed for the investigation of genes associated with quinolone resistance, extendedspectrum β-lactamases, and carbapenemases. Hemolysin and protease production was determined in humanblood agar and skimmed-milk agar, respectively. In the in vivo assay, different doses of P26 were injected intoGalleria mellonella larvae and their survival was monitored daily. Control larvae injected with Pseudomonas putidaKT2440 (a strain considered as safe) and Pseudomonas aeruginosa PA14 (a pathogenic strain) were included.Pseudomonas sp. P26 was susceptible to most evaluated antimicrobials, except for trimethoprimsulfamethoxazole. No epidemiologically relevant genes associated with quinolone and β-lactam resistancewere identified. Hemolysin and protease production was only evidenced in the virulent strain (PA14).Furthermore, the results obtained in the in vivo experiment demonstrated that inocula less than 108 CFU/mL ofP26 and P. putida KT2440 did not significantly affect larval survival, whereas larvae injected with the lowest doseof the pathogenic strain P. aeruginosa PA14 experienced instant mortality. The results suggest that Pseudomonassp. P26 is a safe strain for its application in environmental bioremediation processes. Additional studies will beconducted to ensure the safety of this bacterium against other organisms.