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 (χ2 = 4.97; p = 0.025; Cramer's V = 0.114) and with higher prevalence in casualty (χ2 = 6.89; p = 0.009; Cramer's V = 0.134). A notably greater proportion of carbapenemase-producing isolates were recovered from pus specimens (χ2 = 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 blaNDM-1 as the dominant gene (32.9%), followed by blaOXA-48 (17.1%) and blaVIM (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, blaNDM-1 was prominent in pus, wound swabs, and blood, while blaOXA-48 and blaVIM 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 blaNDM-1 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.