Release of Antibiotic-Resistance Genes from Hospitals and a Wastewater Treatment Plant in the Kathmandu Valley, Nepal

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.

Prevalence of antibiotic resistance genes in drinking and environmental water sources of the Kathmandu Valley, Nepal

“…In Nepal, 74% of the hospitals do not have wastewater treatment facilities ( Joshi et al, 2017 ). Direct discharge of untreated municipal and hospital wastewaters and improperly treated wastewater to rivers in highly populated areas were the possible reasons for this observation ( Acharya and Wilson, 2019 ; Thakali et al, 2020 , 2021 ). A low level of ARG contamination at KTM289, the upstream site of the Bagmati River, and KTM374, the upstream site of the Godavari River, with low population density corroborate this.…”

“…Genes conferring resistance to commonly used antibiotics in this region were selected for the analysis (Thakali et al, 2020(Thakali et al, , 2021. ddPCR was employed in quantifying the ARGs from the drinking water sources and environmental samples speculating that ARG concentrations in drinking water sources may be low, and quantitative PCR (qPCR) may provide below the detection limit results.…”

“…A recent review on the ARB in the human health sector of Nepal has reported high percentages of resistant strains to antibiotics, including cotrimoxazole, ciprofloxacin, ciprofloxacin, tetracyclin, erythromycin, and nalidixic acid ( Acharya and Wilson, 2019 ). sul1, tet (B), bla CTX–M , bla NDM –1 , and qnrS genes were detected in hospital effluents, wastewater treatment plant effluents, and river water, emphasizing the impact of untreated and improperly treated wastewater in contaminating aquatic environments ( Thakali et al, 2021 ). bla TEM , ermF, mecA , and tet (A) genes were detected from the middle and downstream samples of the Bagmati River flowing through the Kathmandu Valley, confirming the anthropogenic contribution ( Thakali et al, 2020 ).…”

“…Therefore, in this study, we evaluated the ARG concentrations in drinking water sources (surface water and groundwater) and environmental waters in the Kathmandu Valley using the droplet digital polymerase chain reaction (ddPCR) method. sul1, tet (A), tet (M), bla KPC , bla OXA , mecA, qnrA, qnrS , and intI1 genes were selected based on previous studies reporting their presence in other aquatic samples ( Thakali et al, 2020 , 2021 ). A number of hospitals and animal health-related studies have reported the high prevalence of bacterial strains resistant to cotrimoxazole, vancomycin, and aminoglycosides ( Nepal et al, 2012 ; Acharya and Wilson, 2019 ; Central Veterinary Laboratory, 2021 ; Pandey et al, 2021 ).…”

Resistant Genes and Multidrug-Resistant Bacteria in Wastewater: A Study of Their Transfer to the Water Reservoir in the Czech Republic

“…It is considered a rare ARG (only 0.0001% of the total ARGs) [41]. Recently, however, it has become increasingly common in wastewater [20,44,45], indicating a high degree of risk of carbapenem resistance.…”