First Report of blaNDM-1, blaOXA-23, and blaOXA-24 Genes in Carbapenem-Resistant A. baumannii from Clinical and Community Specimens in Imo State, Nigeria

Abstract Acinetobacter baumannii is a Gram-negative bacterium known for causing hospital-acquired infections and showing increasing resistance to multiple antibiotics. This study is the first to explore the epidemiology and molecular characteristics of A. baumannii in Imo State, Nigeria, focusing on resistance genes and regional variations. A total of 948 clinical and community specimens (urine, sputum, wounds) were collected from Owerri, Orlu, and Okigwe zones using a systematic random sampling method. A. baumannii identification was conducted through CHROMagar Acinetobacter plates, and 16S rRNA sequencing. Antimicrobial susceptibility testing followed standard guidelines. Only multidrug-resistant A. baumannii isolates, resistant to three or more antibiotic classes and both imipenem and meropenem, were selected for molecular characterization of carbapenemase-encoding genes (blaNDM−1, blaOXA−23, and blaOXA−24). A. baumannii prevalence was 31.9% in community specimens and 27.7% in clinical specimens, with wound samples showing the highest positivity rates. Based on the MDR criteria, only 17 isolates met the requirements and were selected for molecular characterization of carbapenemase-encoding genes. Owerri exhibited the highest prevalence of blaOXA−23 and blaNDM−1, Okigwe had the lowest resistance burden while blaOXA−24 was detected in both clinical and community specimens, indicating local dissemination of resistant strains. These findings highlight the importance of localized surveillance, targeted infection control measures, and antimicrobial stewardship to curb the spread of multidrug-resistant A. baumannii, particularly beyond healthcare settings.