Phylogenomic structure and resistance profiles of clinical Proteus mirabilis from a Thai hospital.

Proteus mirabilis is an opportunistic pathogen associated with urinary tract infections, wound infections, and bacteremia. We analyzed 17 clinical isolates collected from hospitals in Narathiwat Province, southern Thailand, to characterize their antimicrobial resistance (AMR), virulence potential, plasmid replicon content, and genomic relatedness. Most isolates were phenotypically susceptible to all tested antibiotics. Resistance was limited to two strains: KS160 (ceftriaxone, ciprofloxacin, levofloxacin) and KS044 (ciprofloxacin, levofloxacin). Whole-genome analysis, however, identified 50 unique AMR genes, including determinants associated with aminoglycoside, chloramphenicol, trimethoprim, sulfonamide, and quinolone resistance. PlasmidFinder identified IncQ1- and Col3M-replicon-associated contigs. The quinolone resistance gene qnrD1 was detected on highly similar Col3M-associated contigs in two isolates, indicating the occurrence of related putative mobile genetic elements among the clinical isolates. Virulence gene profiling showed a conserved core associated with motility, chemotaxis, LPS/capsule biosynthesis, and stress adaptation. KS155 exhibited the most distinct virulence-gene detection profile, with several motility- and stress response-associated genes not detected above the predefined threshold. Phylogenomic, ANI, and dDDH analyses confirmed that all isolates belonged to P. mirabilis. Although KS155 exhibited the lowest ANI values (96-97%) relative to the other isolates, it represented the greatest genomic divergence among the isolates analyzed. Our findings provide evidence that P. mirabilis circulating in southern Thailand exhibits genetic diversity, maintains a stable core of intrinsic virulence traits, and harbors additional, variably distributed AMR determinants associated with putative mobile genetic elements, emphasizing the importance of continued genomic surveillance in this region.