Genotypic and Phenotypic Landscape of Carbapenem-Resistant Pseudomonas aeruginosa Isolated From Respiratory and Non-Respiratory Samples in a Tertiary Hospital

Abstract Background The World Health Organization lists carbapenem-resistant Pseudomonas aeruginosa (CRPA) as a critical priority, yet links among resistance, virulence, and clonal spread remain unclear. We aimed to characterise the genotypic and phenotypic landscape of clinical CRPA and test whether specimen source or type III secretion effectors exoT/exoY predict antibiotic resistance. Methods Fifty-eight consecutive CRPA isolates from respiratory and non-respiratory specimens were analysed. Susceptibility to 10 agents was determined with an automated system. Seven carbapenemase genes, six virulence/quorum-sensing genes, and the efflux marker mexY were screened by PCR. Macrorestriction patterns were typed by SpeI PFGE. Associations were assessed using two-tailed Fisher’s exact tests with Benjamini–Hochberg false-discovery-rate correction (α = 0.05). Results Resistance was highest to piperacillin/tazobactam (91%), ceftazidime (81%) and cefepime (81%); 34% of isolates were pan-drug-resistant. Only three strains (5%) carried blaVIM; no additional carbapenemase genes were detected. Virulence markers were frequent (exoY 66%, exoT 57%, algD 45%; lasR 91%, rhlR 95%). After FDR adjustment, neither exoT, exoY nor specimen origin correlated with β-lactam, aminoglycoside, or fluoroquinolone resistance (lowest q = 0.093); gene prevalence did not differ between respiratory and non-respiratory isolates (lowest q = 0.65). PFGE revealed 41 pulsotypes without a dominant clone, suggesting sporadic horizontal gene transfer rather than clonal expansion. Conclusions This CRPA cohort is genetically diverse, multidrug-resistant, and anatomically non-segregated. exoT/exoY status does not shape resistance phenotypes. Infection-control strategies should prioritise containment of mobile genetic elements and genome-based surveillance rather than focusing on specific clones or body sites.