Identification of β-lactam-resistant coding genes in the treatment plant by activated sludge process

Abstract

Wastewater treatment plants are the most important release source of antibiotic-resistance genes (ARGs) into the environment. This study aimed to identify β-lactam-resistance genes in Qom province municipal wastewater and also to determine the effect of municipal wastewater treatment plants with different processes on reducing these pollutants. Sampling was performed according to the standard protocol and at constant temperature conditions. Nine genes resistant to the six groups of β-lactam antibiotics were selected, and polymerase chain reaction (PCR) test was performed to identify the presence/absence of ARGs. At the same time, real-time PCR test was also carried out to quantitatively measure three ARGs in wastewater and effluent samples. The obtained results showed that the highest and the lowest removal were related to blanps-1 (90.61%) and blaCTX-M-32 (65.93%), respectively; however, a decreasing trend in these two genes were showed in to blaoxa-1 with an increase in effluent unit (45.12%). The results showed that conventional biological wastewater treatment processes not only have little potential to reduce antibiotic-resistance genes during the treatment process but also these processes sometimes increase resistant genes. The results of the oxa-1 gene in this study are consistent with this trend. In addition, the sludge treatment unit was based on the results of sequencing Salmonella enterica and Klebsiella pneumoniae. Our study suggests that wastewater treatment plants using conventional chlorination do not favor the proliferation of antibiotic resistance bacteria and ARGs during wastewater treatment. Thus, equipping treatment plants with advanced processes will be efficient in reducing bacterial resistance.