Resistotyping and extended-spectrum beta-lactamase genes among Escherichia coli from wastewater treatment plants and recipient surface water for reuse in South Africa

The spread of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli has increased in different environments. This study aimed to evaluate the patterns of antibiotic resistance and ESBL genes among E. coli isolates collected from wastewater and recipient surface water in South Africa. Fifteen samples containing nine wastewater and six river water samples were collected from a local wastewater treatment plant. The E. coli isolates were detected using standard microbiology methods. Antibiotic susceptibility testing was performed using disc diffusion agar. The occurrence of bla(CTX-M), bla(SHV) and bla(TEM) ESBL genes was investigated by PCR. Exactly 140 isolates were selected from the primary enumeration plates with a log(10) CFU/mL count that ranged from 4.1 to 4.2 (influent), 4.2 to 4.5 (biofilter) and 2.5 to 3.3 (effluent). The wastewater effluent showed an impact on the receiving water environment, as the treatment efficiency was 92% and the downstream log(10) CFU/mL count (range, 3.6-3.8 log(10) CFU/mL) was higher than the upstream count (range, 3.3-3.6 log(10) CFU/mL). Antibiotic testing results showed that 40% to 100% of E. coli isolates were resistant to ampicillin, penicillin, tetracycline and cefotaxime but susceptible to imipenem, meropenem and ciprofloxacin. A total of 40 studied isolates (28.6%) had both the bla(TEM) and bla(CTX-M) genes, while no bla(SHV) was detected. The wastewater treatment plants contributed multidrug-resistant ESBL-producing E. coli isolates that can be potential environmental health risks. Regular monitoring policies are recommended to prevent the spread of antibiotic resistance in the region. (C) 2020 The Authors. Published by Elsevier Ltd.