Genomic survey uncovers the emergence of a multidrug-resistant dominant lineage in Proteus mirabilis populations

Abstract Proteus mirabilis , a Gram-negative bacterium renowned for its distinctive swarming motility, is a major causative agent of catheter-associated urinary tract infections (CAUTIs) and nosocomial complications. While advances in sequencing technologies have generated extensive genomic data, critical gaps persist in understanding the global population structure and evolutionary drivers of antimicrobial resistance in this pathogen. To address this knowledge gap, we performed a phylogenomic analysis of 1,142 P. mirabilis genomes spanning 34 countries and 16 ecological niches. Our investigation identified a dominant multidrug-resistant lineage (Cluster-1) carrying significantly elevated antimicrobial resistance gene burdens, including high-prevalence carbapenemase genes bla KPC-2 and bla IMP-27 . Bayesian evolutionary dating traced the most recent common ancestor of Cluster-1 to approximately 1910, with subsequent expansion linked to acquisition of the autotransporter gene agn43 within the PmGRI1 genomic island. Notably, Cluster-1 diversified into two clinically significant subclades: a China-associated branch carrying bla KPC-2 and a USA-associated branch harboring bla IMP-27 . Functional characterization revealed that agn43 deletion caused significant attenuation in biofilm formation, heat stress tolerance, and swarming motility. Our findings delineate the emergence of a globally disseminated P. mirabilis clone, highlighting the synergistic role of antimicrobial resistance and agn43 -mediated adaptive traits in its epidemiological success.