Prevalence and dynamics of quinolone and macrolide resistance in hospital wastewater: insights from Kathmandu Valley, Nepal.

BACKGROUND

Hospital wastewater (HWW) serves as a critical reservoir for antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs), especially those conferring resistance to quinolones, fluoroquinolones and macrolides. This study investigated the prevalence and seasonal dynamics of ARB and ARGs in HWW from the Kathmandu Valley, Nepal.

METHODS

We collected and analysed 16 untreated HWW samples from eight hospitals during the summer and winter seasons (2022-2023). Physicochemical parameters, prevalence of ARB, selected ARGs (qnrS, aac(6')-Ib-cr, erm(B)) and class 1 integron (intI1) were assessed. Results were compared by hospital type and season.

RESULTS

Significant seasonal differences were observed in temperature (P = 0.00024) and total suspended solids (P = 0.042). Klebsiella pneumoniae (31.67%) and Escherichia coli (28.33%) were the most frequently isolated ARB. K. pneumoniae exhibited very high resistance to ciprofloxacin (97.74%) and levofloxacin (89.47%). Among the targeted genes, the aac(6')-Ib-cr gene was the most prevalent (55.67%), followed by intI1 (50%), qnrS (25%) and erm(B) (11.67%). The erm(B) gene was significantly more prevalent in medium-sized hospitals (P = 0.001). No significant seasonal variation was observed for ARGs or the mobile genetic elements (P > 0.05). Although not statistically significant, strong correlations were observed between qnrS prevalence and pH (ρ = 0.912) and ammonia (ρ = 0.812), suggesting potential environmental influences on the dissemination of resistance.

CONCLUSION

The HWW is a significant antimicrobial resistance reservoir, emphasizing improved wastewater treatment and antibiotic stewardship to mitigate resistance dissemination.