Comprehensive Phenotypic and Molecular Analysis of β-Lactamase Enzymes and Genetic Diversity in <i>Proteus mirabilis</i> Clinical UTI Isolates

Abstract

Background: Proteus mirabilis is a major opportunistic pathogen and a leading cause of urinary tract infections (UTIs). The emergence of multidrug resistance, particularly β-lactamase-mediated mechanisms, including extended-spectrum β-lactamases (ESBLs), AmpC β-lactamases, and carbapenemases, complicates treatment efficacy worldwide. Objectives: This study aimed to determine the genotypic prevalence of β-lactamase genes as the primary outcome and to assess their statistical association with phenotypic resistance profiles. Secondary objectives included evaluating multidrug resistance (MDR) prevalence and clonal diversity. Methods: Sixty P. mirabilis isolates were confirmed by PCR of the urea gene. Antimicrobial susceptibility testing was performed according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Phenotypic screening for ESBL, AmpC, and carbapenemase production was conducted. Multiplex PCR targeted blaTEM, blaSHV, blaAmpC, blaFOX, and blaKPC. As an exploratory analysis, Enterobacterial Repetitive Intergenic Consensus-PCR (ERIC-PCR) was used to assess genetic relatedness. Statistical associations were evaluated to identify key molecular drivers of resistance. Results: The primary outcome showed a high prevalence of blaTEM (98.3%), followed by blaSHV (23.3%), blaFOX (8.3%), and blaKPC (5%). Significant associations were observed between blaKPC and carbapenem resistance (P < 0.001). Phenotypic ESBL, AmpC, and carbapenemase production (secondary outcomes) were detected in 68.3%, 51.6%, and 10% of isolates, respectively. Overall, 55% of isolates were MDR. ERIC-PCR identified 15 clusters, indicating high genetic diversity. Conclusions: Our findings confirm that specific β-lactamase genotypes are strongly associated with clinical resistance patterns. The high prevalence of MDR strains harboring diverse resistance genes underscores the need for molecular surveillance and optimized stewardship to control resistance dissemination.