Pollution characteristics of antibiotics and antibiotic resistance of coliform bacteria in the Yitong River, China

In this study, the concentrations of nine typical antibiotics, including sulfadiazine (SD), sulfamerazine (SMR), sulfamethazine (SM2), sulfamethoxazole (SMZ), ofloxacin (OFX), ciprofloxacin (CIP), trimethoprim (TMP), oxytetracycline (OTC), and tetracycline hydrochloride (TC), were detected in the Yitong River by solid-phase extraction high-performance liquid chromatography. The concentrations of the antibiotics were analyzed. Additionally, an improved immobilized substrate enzyme substrate method (DST-enzyme substrate method) was developed and used to evaluate the antibiotic resistance of coliform bacteria to OFX, CIP, enrofloxacin (ENR), TC, sulfisoxazole (SOX), and TMP in the Yitong River. The results showed that the concentrations of the nine antibiotics ranged from nd (not detected) to 1.361 μg/L. The detection rate and concentration of OFX were the highest, followed by CIP, and the detection rate and concentration of SM2 and OTC were the lowest. The detection rate and concentrations of antibiotics were higher in August and November than those in May. The antibiotics were mainly distributed in the livestock sewage discharge and suburban domestic sewage discharge areas. Moreover, the drug resistance of total coliform bacteria to fluoroquinolones, sulfonamides, tetracyclines, and TMP varied with season.