Bacteriophage facilitated transmission of multidrug efflux pump regulatory genes in Pseudomonas aeruginosa.

The emergence of multidrug-resistant Pseudomonas aeruginosa strains, primarily driven by efflux pumps that expel antibiotics, poses a serious global health threat. Phages, particularly members of the class Caudoviricetes (94.7 %), play a significant role in the horizontal transfer of genetic material among bacterial hosts, potentially contributing to the acquisition and spread of antibiotic resistance genes. In this study, analysis of 6712 P. aeruginosa genomes from the JGI-IMG/VR virus database revealed that all P. aeruginosa RefSeq genome assemblies (GCF accessions) contained efflux pump genes (MexAB-oprM, MexCD-oprJ, and MexEF-oprN) as well as their associated regulatory genes (mexT, mexR, and nfxB). Notably, these genes can be transmitted through phage-mediated horizontal gene transfer, as evidenced by their detection in viral sequences. Among phages harboring these genes, 43.9 % were identified as lysogenic. These phages were predominantly associated with aquatic (33.2 %), human (19.0 %), and terrestrial (16.4 %) environments worldwide, highlighting the potential risks of environmental contamination. Experimental validation using PA1 and PAO1 strains confirmed the role of phages in facilitating horizontal gene transfer. These findings highlight the urgent need to implement surveillance and mitigation measures targeting phage-associated antibiotic resistance dissemination, with direct implications for both public health and environmental safety.