Coexistence of Multidrug Resistance and Hypervirulence-Associated Genes in Clinical Carbapenem-Resistant <i>Pseudomonas aeruginosa</i>

The recent worldwide emergence of hypervirulent, multidrug-resistant <i>Pseudomonas aeruginosa</i> represents a critical public health threat. The molecular typing, multidrug resistance (MDR) rates, and hypervirulence-associated genes in carbapenem-resistant <i>P. aeruginosa</i> (CRPA) isolates can vary across geographic locations and patients, highlighting their clinical significance. In this study we investigated the epidemiology and relationship between MDR and the presence of hypervirulence-associated genes in CRPA isolates. Accordingly, we performed antimicrobial susceptibility tests, multilocus sequence typing (MLST), and PCR-based detection of carbapenemase and virulence-associated genes. Notably, 34.9% (139/398) of the isolates were carbapenem-resistant, with 79.1% of these exhibiting MDR. Of the 30 sequence types (STs) identified by MLST, ST773 was the most prevalent (28.8%), followed by ST235 (23.0%). New Delhi metallo-β-lactamase (NDM)-1 or imipenemase-6 occurred in 45.3% of the CRPA strains. Common virulence genes included <i>exoT</i> (100.0% of isolates), <i>exoY</i> (95.7%), <i>exoU</i> (66.2%), and <i>exoS</i> (34.5%). <i>exoU</i> was associated with antibiotic resistance (<i>p</i><0.05), except for carbapenems in CRPA isolates. The <i>exoU</i>/<i>exoT</i>/<i>exoY</i> Type III secretion system (T3SS) genotype was the most prevalent among the carbapenemase-producing CRPA strains. Among the 139 CRPA isolates, we identified a pandrug-resistant, NDM-1-producing ST235 strain co-expressing <i>exoS</i> and <i>exoU</i>. This study highlights the important association between <i>exoU</i> and MDR, indicating a potential relationship between T3SS genotypes and antibiotic resistance. Additionally, the identification of a hypervirulent, pandrug-resistant <i>P. aeruginosa</i> ST235 isolate harboring <i>bla</i>_IMP-6 underscores the critical need for enhanced surveillance against high-risk strains.