Epidemiological and molecular characterisation of carbapenemase-producing Pseudomonas aeruginosa from a tertiary care hospital, India.

This study investigates the epidemiological and molecular characteristics of carbapenemase-producing Pseudomonas aeruginosa among 382 clinical isolates. Carbapenemase production was significantly associated with male gender (χ = 4.97; p = 0.025; Cramer's V = 0.114) and with higher prevalence in casualty (χ = 6.89; p = 0.009; Cramer's V = 0.134). A notably greater proportion of carbapenemase-producing isolates were recovered from pus specimens (χ = 5.50; p = 0.019; Cramer's V = 0.120), suggesting specific tissue tropism. Antibacterial susceptibility profiling revealed high resistance to β-lactams (e.g. cefepime (40.2%), ceftazidime (42.4%)) and fluoroquinolones (ciprofloxacin (36.5%), levofloxacin (38.9%)), while colistin (84.4%) and amikacin (83.1%) retained high efficacy. Among carbapenem-resistant strains (n = 258), multidrug resistance (MDR) was most prevalent (55.4%), followed by extensively drug-resistant (XDR, 35.7%) and pan-drug-resistant (PDR, 8.9%) phenotypes. Molecular analysis of 164 resistant isolates identified bla as the dominant gene (32.9%), followed by bla (17.1%) and bla (9.1%). Co-expression patterns were frequent, with dual and triple gene combinations suggesting horizontal gene transfer and clonal dissemination. Gene distribution showed male predominance and high prevalence in ICU, Surgery, and TB & Chest departments, indicating critical hotspots for MDR containment. Specimen-wise, bla was prominent in pus, wound swabs, and blood, while bla and bla were enriched in sputum, pleural fluid, and BAL. The triple gene combination was most prevalent in BAL and urine samples. These findings highlight a high burden of carbapenem resistance, driven by bla and its combinations, with significant clinical and infection control implications. Robust antibacterial stewardship and targeted surveillance in high-risk departments are imperative to curb the spread of these highly resistant pathogens.