Genomic Characterization of a Class 2/1 Hybrid Integron-Driven Multidrug-Resistant Proteus mirabilis SH-8 of Swine Origin

Objective: P. mirabilis is a Gram-negative rod-shaped bacterium. In this study, the SH-8 strain of P. mirabilis was isolated from swine-derived samples, and its antibiotic resistance genes (ARGs) and transmission mechanisms were systematically characterized. Methods: The minimum inhibitory concentrations (MICs) of strain SH-8 were determined by the broth microdilution method, with genomic features analyzed through whole-genome sequencing (WGS). Results: P. mirabilis SH-8 exhibited resistance to multiple antimicrobial agents. Its genome consists of a single chromosome (3,993,987 bp; GC content 38.8%) and one plasmid. WGS identified 21 distinct ARGs in this strain, along with a class 2/1 hybrid integron. Furthermore, a heatmap analysis of resistance genes from 29 P. mirabilis isolates of diverse origins revealed a striking similarity between the resistance gene profile of SH-8 and those of other strains. Conclusions: The MDR exhibited by P. mirabilis SH-8 is primarily attributed to integron-mediated resistance gene clusters within its genome, which may pose challenges for treating opportunistic infections caused by this bacterium.