Screening and Absolute Quantification of a β-lactamase Resistance Gene NDM-1 in Lake Sediment

Abstract The extensive usage of antibiotics in humans and veterinary medicine and their discharge into the aquatic environment hasten the growth, selection, and horizontal transmission of ARGs in a given bacterial community. New Delhi Metallo-β-lactamase-1(NDM-1) is an enzyme that hydrolyzes a wide range of β-lactams antibiotics, including carbapenems. The rapid distribution of NDM-1 harboring bacteria accounts for a significant public health menace worldwide. The presence of the NDM-1 inhibited the potential of β–lactam antibiotics for treating infections caused by bacterial strains carrying such resistances, leaving minimal treatment options available. NDM-1 harboring bacteria have been detected in clinical specimens and environmental compartments where bacterial infections are ubiquitous. In this study, identification and absolute quantification of NDM-1 in sixteen lake sediment samples collected in and around Hyderabad, India, was carried out using a real-time quantitative polymerase chain reaction (qPCR) and results were expressed in gene copy number/ng (nanogram) of template DNA. 13 samples (out of 16) shown a positive signal for NDM-1 during qPCR analysis. Durgamcheru lake, Kandi lake, and Singur dam showed a negative signal for the NDM-1 during qPCR analysis among the tested samples. The remaining sampling locations tested positive with the highest gene copy number/ng of template DNA observed in the Amberpet STP (71.8). Hierarchical clustering analysis was performed to categorize the sampling location into different clusters based on pollution sources and observed results expressed in the form of a dendrogram.