Abstract

Hospitals and wastewater treatment plants (WWTPs) are high-risk point sources of antibiotic-resistance genes (ARGs) and antibiotic-resistant bacteria. This study investigates the occurrence of clinically relevant ARGs (sul1, tet(B), blaCTX-M, blaNDM-1, qnrS) and a class one integron (intI1) gene in urban rivers, hospitals, and municipal wastewater in the Kathmandu Valley, Nepal. Twenty-five water samples were collected from three rivers, six hospitals, and a wastewater treatment plant to determine the concentrations of ARGs and intI1 using quantitative polymerase chain reactions. From the results, all tested ARGs were detected in the river water; also, concentrations of ARGs in WWTP and hospital effluents varied from 6.2 to 12.5 log10 copies/L, highlighting the role of a WWTP and hospitals in the dissemination of ARGs. Except for blaNDM-1, significant positive correlations were found between intI1 and other individual ARGs (r = 0.71–0.96, p < 0.05), indicating the probable implications of intI1 in the transfer of ARGs. Furthermore, this study supports the statement that the blaNDM-1 gene is most likely to be spread in the environment through untreated hospital wastewater. Due to the interaction of surface water and groundwater, future research should focus on ARGs and factors associated with the increase/decrease in their concentration levels in drinking water sources of the Kathmandu Valley.

Highlights

  • Antibiotic resistance is one of the biggest threats to global health today and is primarily driven by the overuse of antibiotics

  • Valley throughout the year, showing rivers in the valley are polluted with antibiotic-resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) [10]

  • The relative abundance, as shown in Figure 2, was similar in all urban rivers. sul1 showed the highest relative abundance (p < 0.05), whereas the lowest was observed for blaNDM-1

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Summary

Introduction

Antibiotic resistance is one of the biggest threats to global health today and is primarily driven by the overuse of antibiotics. Between 2000 and 2015, antibiotic consumption increased by 65% and is further expected to increase by 200% in 2030 unless significant policy changes are made. The increase in antibiotic consumption was majorly driven by increased usage in low and middle-income countries [1]. The biodegradability test of antibiotics conducted in wastewater has shown that antibiotics were not degraded in wastewater, resulting in the selection pressure of bacteria [4]. Extensive use of antibiotics for treatment results in the emission of large quantities of antibiotic residues and antibiotic-resistant bacteria (ARB) from hospitals [5]

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