Analysis of Wastewater Reveals the Spread of Diverse Extended-Spectrum β-Lactamase-Producing E. coli Strains in uMgungundlovu District, South Africa.

Siyabonga N Gumede,Akebe L K Abia,Daniel G Amoako,Sabiha Y Essack

doi:10.3390/antibiotics10070860

Abstract

Wastewater treatment plants (WWTPs) are major reservoirs of antibiotic-resistant bacteria (ARB), favouring antibiotic resistance genes (ARGs) interchange among bacteria and they can provide valuable information on ARB circulating in a community. This study characterised extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli from the influent and effluent of four WWTPs in uMgungundlovu District, KwaZulu-Natal, South Africa. E. coli was enumerated using the membrane filtration method and confirmed using the API 20E test and real-time polymerase chain reaction. ESBL-producers were phenotypically identified by their susceptibility to the third-generation cephalosporins using the disc diffusion and the double-disc synergy methods against cefotaxime (30 µg) with and without 10 µg clavulanic acid. Genotypic verification was by PCR of the TEM, SHV, and CTX-M genes. The clonality of isolates was assessed by ERIC-PCR. The highest E. coli count ranged between 1.1 × 105 (influent) and 4.3 × 103 CFU/mL (effluent). Eighty pure isolates were randomly selected, ten from the influent and effluent of each of the four WWTP. ESBLs were phenotypically confirmed in 49% (n = 39) of the isolates, of which 77% (n = 30) were genotypically confirmed. Seventy-three percent of the total isolates were multidrug-resistant (MDR). Only two isolates were susceptible to all antibiotics. Overall, resistance to first and second-generation cephalosporins was higher than to third and fourth generation cephalosporins. Also, 15% of the isolates were resistant to carbapenems. The CTX-M-type ESBL (67%; n = 20) was the most common ESBL antibiotic resistance gene (ARG) followed by TEM (57%; n = 17) and SHV-types (27%; n = 8). Also, a substantial number of isolates simultaneously carried all three ESBL genes. ERIC-PCR revealed a high diversity of isolates. The diversity of the isolates observed in the influent samples suggest the potential circulation of different ESBL-producing strains within the studied district, requiring a more comprehensive epidemiological study to prevent the spread of ESBL-producing bacteria within impoverished communities.

Highlights

This study demonstrated diverse extended-spectrum beta-lactamase (ESBL)-producing E. coli circulating within South African communities and the subsequent discharge of these bacteria by wastewater treatment plants (WWTPs) into receiving surface waters
The current study demonstrated the ubiquity of antibiotic-resistant ESBLs-producing
E. coli in the uMgungundlovu District by examining four major WWTPs

Summary

Introduction

Antibiotic resistance is one of the major public health concerns globally. This is commonly demonstrated in bacteria such as E. coli, found on the WHO global priority list of antibiotic-resistant bacteria to guide research, discovery, and development of new antibiotics [1,2]. Today [6,7,8] and are frequently associated with a high mortality rate and prolonged hospitalisation [9,10]. This may be because clinical E. coli isolates frequently co-carry multiple

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Conclusion