Six-Year Longitudinal Surveillance of Multidrug-Resistant Klebsiella oxytoca in a Tertiary Care Hospital in Central India: Resistance Trends, Nosocomial Clusters, and Carbapenemase Gene Characterisation.

BACKGROUND: Klebsiella oxytoca is an underrecognised nosocomial pathogen with growing multidrug resistance (MDR). Longitudinal surveillance data from Indian tertiary care hospitals remain scarce. We characterised six-year resistance trends, nosocomial transmission dynamics, and carbapenemase gene profiles of K. oxytoca at a large teaching hospital in central India. METHODS: A prospective longitudinal observational study was conducted at Gandhi Medical College and Associated Hamidia Hospital, Bhopal (January 2020-December 2025). Non-duplicate inpatient K. oxytoca isolates (n=1,203) were included. Antimicrobial susceptibility used Kirby-Bauer disk diffusion; MDR and extensively drug-resistant (XDR) phenotypes were classified per Magiorakos et al. Nosocomial clusters were identified by WHONET-SaTScan (Space-Time Permutation model). Antibiotic consumption was quantified as defined daily doses per 100 patient-days. Carbapenem resistance in 67 cluster-associated isolates was characterised by singleplex PCR for blaNDM, blaOXA-48, and blaKPC. RESULTS: K. oxytoca comprised 2.8% of inpatient specimens (incidence density 0.38/1,000 bed-days). MDR and XDR rates were 85.1% and 76.0% respectively. Carbapenem resistance rose from 46.0-50.0% (2020) to 73.0-73.5% (2025); ICU isolates had higher MDR rates than ward isolates (89.6% vs. 83.3%; p=0.008). Colistin susceptibility was preserved in 99.6% of isolates. Six significant spatiotemporal clusters were identified; the largest (observed-to-expected ratio 7.4) involved medical ICUs in 2024. blaNDM was detected in 89.6% of carbapenem-resistant cluster isolates, with blaNDM/blaOXA-48 co-carriage in 41.8%. CONCLUSIONS: This study documents progressive escalation of carbapenem resistance and nosocomial transmission of K. oxytoca in a large Indian teaching hospital, driven by NDM-type carbapenemases and dual-gene co-carriage. These findings support strengthening of molecular surveillance, infection prevention, and antimicrobial stewardship at Indian tertiary care centres.