Prevalence and Molecular Epidemiology of Carbapenem-Resistant Organisms in Intensive Care Units of Selected Tertiary Hospitals in South East Nigeria

Carbapenem-resistant organisms (CROs) represent the highest-priority antimicrobial resistance threat in clinical settings globally, yet their prevalence and molecular characteristics in South East Nigerian ICU environments remain uncharacterised. This study determines the prevalence and molecular epidemiology of carbapenem-resistant organisms in ICUs of three tertiary hospitals in Imo, Enugu, and Ebonyi States, South East Nigeria. Surveillance cultures were collected from ICU patients' blood, urine, and respiratory specimens alongside environmental samples from ventilators, sinks, and bedrails over six months. Carbapenem-resistant phenotypes were confirmed by modified carbapenem inactivation method and metallo-beta-lactamase Etest. Carbapenemase genes (blaKPC, blaNDM, blaOXA-48, blaVIM) were detected by multiplex PCR. CRO prevalence was 21 percent of all gram-negative isolates across the three ICUs. NDM-1-producing Klebsiella pneumoniae was the predominant CRO, accounting for 58 percent of confirmed carbapenemase producers. OXA-48-like producers were identified in 22 percent of CROs. Environmental samples yielded identical CROs to clinical isolates in two hospitals, confirming hospital-wide transmission. Whole genome sequencing of eight representative isolates confirmed clonal expansion of NDM-1 K. pneumoniae within and between facilities. The study constitutes the first CRO molecular epidemiology study from South East Nigerian ICUs and informs urgent infection control and treatment policy. Keywords: carbapenem resistance, NDM-1, ICU, South East Nigeria, Klebsiella pneumoniae