Sulfonamide and tetracycline resistance genes in nanjing lakes: effect of water quality and heavy metals

Due to high population density, anthropogenic activities and waste disposal have negatively affected artificial lakes in residential areas. These artificial lakes lack the capacity for auto-depuration to remove pollutants and contaminants; thus, they have the potential to act as reservoirs for antibiotic resistance genes (ARGs). In this study, we examined three urban artificial freshwater lakes in Nanjing to determine the abundance of sulfonamide and tetracycline resistance genes. Concerning water quality, the three lakes were found to be highly eutrophic, owing to their high levels of Total Nitrogen (TN), Phosphorous (TP), and Chlorophyll a (Chla). The average abundance of sulfonamide resistance genes detected in the three urban lakes was 42.446 log(10) gene copies/100 ml, which was lower than the average abundance of tetracycline resistance genes (68.207 log(10) gene copies/100 ml). Analysis by ANOVA revealed that all ARGs, except sul3, showed significant differences, probably due to varied anthropogenic influences in lakes. Pearson correlation and principal component analyses were performed to explore the correlation between ARGs, water quality markers, and heavy metals to understand the co-selection and drivers of ARGs propagation. tetM showed no correlation with any water quality markers, whereas Chla showed a positive correlation with all ARGs except tetM. tetM was the only gene observed to be unaffected by TN, TP, and Chla. The tet genes also showed strong associations with each other except tetM, especially tetA, tetQ, and tetG. The co-selection results between heavy metals and ARGs were insignificant (p > 0.05), with tetM being the most sensitive to the effects of heavy metals and As having the strongest effect on sul3 and tet genes. The results from this study provide basic but archival information on the effect of eutrophication and heavy metals such as Arsenic, showing the potential influence on the dissemination of certain sulfonamide and tetracycline ARGs in freshwater environments.