Molecular characterization of metallo-beta-lactamase producers among carbapenem-resistant Pseudomonas aeruginosa from clinical samples in a tertiary care hospital, Lucknow, India.

Pseudomonas aeruginosa is a significant opportunistic pathogen in healthcare-associated infections. Its intrinsic resistance and ability to acquire resistance genes pose therapeutic challenges, particularly with the emergence of multidrug-resistant (MDR), extensively drug-resistant (XDR), and pan-drug-resistant (PDR) strains. This study aimed to assess the prevalence, antimicrobial susceptibility, and metallo-β-lactamase (MBL) resistance genes (blaNDM, blaOXA48) in P. aeruginosa isolates from clinical samples over 14 months. A total of 4410 clinical samples were processed, yielding 241 non-duplicate P. aeruginosa isolates. Antimicrobial susceptibility testing (AST) identified MDR, XDR, and PDR isolates. Carbapenemase production was detected using the eCIM test, and blaNDM and blaOXA48 genes were identified via PCR. Among the 241 isolates, 128 (53.1%) were from female patients and 113 (46.9%) from males. The most common sample sources were pus 111 (46.1%), sputum 36 (14.9%), and urine 35 (14.5%). The highest prevalence was observed in the Medicine department (45, 18.7%) and TB & Chest (42, 17.4%). Inpatients contributed 126 (52.3%) isolates, while 115 (47.7%) were from outpatients. AST showed the highest sensitivity to piperacillin/tazobactam (70.2%), piperacillin (67.2%), and tobramycin (67.6%), while imipenem (47.7%) and ceftazidime (33.6%) exhibited the lowest sensitivity. MDR was identified in 88 (36.5%) isolates, XDR in 29 (12.0%), and PDR in 9 (3.7%). MDR isolates were most common in pus (33, 13.6%), while XDR and PDR were frequently found in bronchoalveolar lavage (6, 2.4%) and urine (3, 1.2%), respectively. Among 20 eCIM-positive isolates, all carried the blaNDM gene, and 17 (85.0%) harbored blaOXA48. Males accounted for 70.0% of blaNDM and 70.6% of blaOXA48 cases. The highest prevalence of blaNDM (35.0%) was in the 41-60 age group, while blaOXA48 was equally distributed between the 20-40 and 41-60 age groups (35.3% each). Sputum (25.0% blaNDM, 23.5% blaOXA48) and urine (20.0% each) were the most common specimen sources. This study demonstrates the presence of antimicrobial resistance in P. aeruginosa isolates, including MDR, XDR, and PDR strains. The detection of carbapenemase-producing isolates carrying blaNDM and blaOXA-48 genes emphasizes the importance of effective infection control measures, antimicrobial stewardship, and ongoing surveillance to monitor and manage resistance trends.