Occurrence of antibiotic resistance genes and potentially pathogenic bacteria in the Yangtze River tributary (Nanjing section) and their correlation with environmental factors

Abstract

Abstract Freshwater environments are vulnerable to emerging contaminants such as Antibiotic resistance genes (ARGs), and their occurrence is gaining more attention. However, the occurrence of ARGs along with potential pathogens is less explored. The current study aimed to evaluate the abundance of ARGs and explore bacterial communities for the presence of potential bacterial pathogens in water samples collected from a tributary to the Yangtze River in Nanjing. Twelve physico-chemical parameters were analyzed, followed by quantifying 10 ARGs targeting sulfonamide (sul1, sul2), tetracycline (tetG, tetM, tetQ), erythromycin (ermB), vancomycin (vanA, vanR), and streptomycin (strA, strB) using real-time PCR and bacterial diversity characterization using high-throughput 16 S rRNA sequencing. The results indicated poor water quality and high-level eutrophication in most sampling locations. sul1, sul2, and strB were dominant in the study area with average concentrations of 6.8, 7.1, and 6.5 Log10 gene copies/100 ml, respectively. Proteobacteria, Cyanobacteria, Bacteroidetes, and Actinobacteria were the main phyla detected in the study area, and genus-level analysis revealed the presence of eight potential pathogenic and ten fecal-associated bacterial genera at several locations in the study area. The distance-based Redundancy analysis indicated that total phosphorus, electrical conductivity, dissolved oxygen, total dissolved solids, ammonium-N (NH4 +-N), and chlorophyll a had significantly influenced the bacterial community composition in the monitored locations. Correlation analysis demonstrated that water temperature, pH, NH4 +-N, and total organic carbon were positively correlated with sul2, tetG, and vanR genes, indicating that these environmental parameters significantly affected the ARGs distribution pattern. Overall, our results provide valuable information regarding the occurrence of ARGs and potential bacterial pathogens in the study area; however, their co-existence highlights increased human health risks.