Catchment scale analysis of occurrence of antibiotic resistance genes in treated wastewater

Abstract

Antibiotic resistance poses a significant health risk for humans and animals. Wastewater treatment plants (WWTPs) are among the key sources of antibiotic resistance genes (ARGs) in the natural environment. The aim of this study was to analyze the occurrence and seasonal variations of ARGs in treated wastewater flowing to the Pilica River or its tributaries. Samples of treated effluents were collected from 17 WWTPs assigned into three groups based on their population equivalent (PE): <2000, 2000–9999 and 15,000–99,999. Samples were collected four times at two-month intervals between November 2017 and July 2018. The occurrence of the 16S rRNA gene, class 1 integrase (intl1) gene and genes encoding resistance to beta-lactams (blaTEM, blaOXA, blaSHV, blaCTX-M), tetracyclines (tetA, tetB, tetC, tetD, tetE), fluoroquinolones (aac(6′)-Ib-cr), macrolide, lincosamide and streptogramin (MLS) antibiotics (ermF, linA) and sulfonamides (sul1) was determined by standard PCR. All of the analyzed ARGs, excluding blaSHV, were detected in treated wastewater. The prevalence of ARGs was more frequently in spring and rarelier in summer. Antibiotic resistance genes were most frequently detected in treated wastewater flows out from small WWTPs (class I, PE <2000).