Occurrence of Antibiotic-Resistant Bacteria and Their Genes in Bagmati River, Nepal

Polluted river water systems can contribute to the acquisition and propagation of antibiotic resistance in the ecosystem. This study focused on describing the occurrence of antibiotic-resistant bacteria and genes in a river system in relation to the concentration of organic pollutants. Water samples were collected in triplicate from 13 different sampling points of the Bagmati River and analyzed for physicochemical characteristics and antibiotic-resistant bacteria. The presence of antibiotic resistance genes (ARGs) in the isolated organisms was studied using conventional polymerase chain reaction (PCR). It was observed that ARGs and antibiotic-resistance bacteria (ARB) showed a statistically significant positive connection with organic contaminants. The mean ratio of doxycycline, oxytetracycline, and sulphamethoxazole-resistant bacterial population to the total bacterial population was found to be 0.44 ± 0.068, 0.42 ± 0.067, and 0.46 ± 0.087, respectively. Here, 40 bacterial isolates were identified, of which 70% were Escherichia coli , 16% were Klebsiella spp., 5% were Staphylococcus aureus , 3% were Salmonella Typhi, 3% were Pseudomonas aeruginosa , and 3% were Alcaligenes faecalis . Antimicrobial susceptibility testing showed 80% of the bacterial isolates were multi-drug resistant. Frequent detection of selected genes ( tetA and sul1 ) through conventional PCR in the isolates (90.6%) indicated that the river water was heavily contaminated with antibiotic resistance genes. Among the isolates harboring the genes, most of them were found to be phenotypically resistant to the respective antibiotics. The presence of therapeutically pertinent ARGs in the river system shows the necessity of keeping track of environmental antibiotic resistance and corrective measures to overcome challenges.