Emergence of New Delhi metallo-β-lactamase-1 (NDM-1) producing Enterobacterales from water sources: An impending public health challenge in Adamawa-north senatorial zone, Nigeria

Background: The emergence of New Delhi metallo-beta-lactamase-1 (NDM-1) among Enterobacterales in water sources has raised a major public health concern and constitute critical threat to human health as these organisms exhibits high level of resistance to available potent antibiotics. The aim of this study is to detect the presence of NDM-1 gene among carbapenem resistant Enterobacterales (CRE) isolates from water sources. Methodology: A total of 256 water samples were collected from randomly selected hand-dug wells (128 samples) and river/stream (128 samples) for each of dry and rainy seasons in four out of the five local government areas (LGAs) of Adamawa-north senatorial zone, Nigeria. The water samples were filtered using membrane filtration technique and the filters introduced into appropriate bacteriologic media for bacterial growth. The bacterial isolates recovered were identified by both phenotypic and molecular protocols. Phenotypic carbapenem (imipenem) resistance was determined by disc diffusion test, blaNDM-1 gene was detected by specific polymerase chain reaction (PCR) test, and plasmid DNA was extracted and electrophoresed by standard procedure. Results: Of the 256 water samples analyzed for bacteria growth, 300 bacterial isolates of the order Enterobacterales were recovered. Of these, only 45 (12.6%) isolates were phenotypically resistant to carbapenem (imipenem) antibiotic and blaNDM-1 gene was detected in 30 (66.7%) of these. While blaNDM-1 gene was detected in all the isolates of Klebsiella oxytoca, Klebsiella variicola, Enterobacter aerogenes, Enterobacter hormaechei, Enterobacter asburiae, Citrobacter freundii, and Morganella morganii that were resistant to imipenem, other isolates harbored blaNDM-1 gene in varying proportion. Most of the isolates positive for blaNDM-1 also harbored R-plasmids. Conclusion: Emergence of carbapenem resistance mediated by NDM-1 gene in Enterobacterales isolated from water sources constitutes an emerging public health challenge with potential transmission to humans, thereby complicating the treatment of infections caused by these resistant pathogens in man. As such, the urgent need for antimicrobial surveillance and stewardship is of utmost importance.