Carbapenem-resistant and other multidrug-resistant organisms in a South Indian tertiary care centre: A laboratory-based study.

Background and objectives Carbapenem-resistant gram-negative pathogens are associated with limited treatment options and poor clinical outcomes. This study assessed the prevalence, distribution, antimicrobial susceptibility, and clinical outcomes of multidrug-resistant organisms from intensive care units and related wards in a South Indian tertiary care hospital over three years. Methods A retrospective laboratory-based study was conducted between October 2022 to May 2025, analysed culture-positive specimens from the selected locations using hospital information system data. Multidrug-resistant organisms were defined according to international criteria. Organisms included carbapenem-resistant Enterobacterales, carbapenem-resistant Acinetobacter baumannii, carbapenem-resistant Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus spp., and trimethoprim-sulfamethoxazole resistant Stenotrophomonas maltophilia. Demographics, specimen distribution, antimicrobial susceptibility, and outcomes were analysed using descriptive and inferential statistics. Results Of 8,704 specimens processed, 3,450 (39.6%) were culture-positive and 750 (34.2%) were multidrug-resistant. Carbapenem-resistant Enterobacterales accounted for (n=490,65.3%) of multidrug-resistant organisms, followed by carbapenem-resistant Acinetobacter baumannii (n=85,11.3%), carbapenem-resistant Pseudomonas aeruginosa (n=85,11.3%), methicillin-resistant Staphylococcus aureus (n=40,5.3%), vancomycin-resistant Enterococcus spp. (n=34,4.5%), and trimethoprim-sulfamethoxazole-resistant S. maltophilia (n=16,2.1%). Klebsiella pneumoniae predominated among carbapenem-resistant Enterobacterales isolates. Multidrug-resistant organisms were significantly more common in intensive care units (539/750,71.9%) and among patients aged >60 y (399/750,53.2%) (P<0.05). Enterobacterales showed high resistance to cephalosporins and fluoroquinolones, while A. baumannii demonstrated limited meropenem susceptibility (18/110,16.3%). Overall mortality among patients with multidrug-resistant infections was (191/750,25.5%), with 94% (180/191) of deaths clinically attributed to infection. Interpretation and conclusions Carbapenem-resistant Klebsiella pneumoniae and Acinetobacter baumannii are the predominant multidrug-resistant organisms, especially in intensive care units. These highlights the urgent need for strengthened antimicrobial stewardship, infection-control practices and ongoing antimicrobial resistance surveillance.