This study investigated the impact of each treatment stage of the activated sludge process on the fate of antibiotic resistant bacteria (ARB) in wastewater treatment plants (WWTPs). Wastewater and sludge samples were collected monthly at each stage of a commercial-scale WWTP. After 20–25 strains of indicator Escherichia coli were isolated from each sample on Chromocult Coliform Agar, antibiotic resistance of the isolates to amoxicillin (AMX), ciprofloxacin (CIP), norfloxacin (NFX), kanamycin (KM), sulfamethoxazole/trimethoprim (ST) and tetracycline (TC) were tested with the Kirby–Bauer disk diffusion method. As a result, activated sludge in the aeration tank and return sludge had higher abundance of antibiotic resistant E. coli than influent wastewater and secondary treatment effluent. AMX resistant E. coli was enriched in return sludge at the secondary clarifier. Higher temperature was also likely to cause an increase of AMX resistant E. coli in sludge. The antibiotic resistance profile of E. coli in secondary treatment effluent was more dependent on activated sludge than influent wastewater. These results suggested that activated sludge in WWTP possibly serves as a reservoir of ARB, and that behavior of ARB in WWTP differs by antibiotic classes.

这项研究调查了活性污泥工艺的每个处理阶段对废水处理厂（WWTP）中抗药性细菌（ARB）命运的影响。在商业规模污水处理厂的每个阶段，每月都要收集废水和污泥样品。在Chromocult大肠菌琼脂上从每个样品中分离出20-25株指示性大肠杆菌后，分离株对阿莫西林（AMX），环丙沙星（CIP），诺氟沙星（NFX），卡那霉素（KM），磺胺甲恶唑/甲氧苄啶（ST）的抗生素抗性）和四环素（TC）用Kirby-Bauer圆盘扩散法进行了测试。结果，曝气池中的活性污泥和回流污泥具有更高的抗药性大肠杆菌比进水和二级处理出水要多。在二级澄清池中，耐AMX的大肠杆菌富含回流污泥。较高的温度也可能导致污泥中耐AMX的大肠杆菌增加。与进水相比，二级处理废水中的大肠杆菌对抗生素的耐药性更依赖于活性污泥。这些结果表明，污水处理厂中的活性污泥可能充当了ARB的库，而且污水处理厂中ARB的行为因抗生素类别而异。