A public health concern regarding the widespread presence of pathogenic and ESBL-producing Escherichia coli in wastewater-impacted rivers in the Limpopo province of South Africa

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Introduction Antimicrobial resistance (AMR) in river systems is a chronic global environmental and public health issue, caused mostly by poorly treated effluents from wastewater treatment facilities (WWTPs). These discharges transmit antibiotic residues, resistant bacteria, and resistance genes into rivers, exacerbating the problem in poorer nations like South Africa owing to poor WWTP efficiency, inadequate sanitation, overuse of antibiotics, and minimal monitoring. This study investigated the prevalence of diarrheagenic pathotypes and ESBL-producing Escherichia coli in wastewater-impacted rivers in seven catchments in Vhembe District Municipality, Limpopo, South Africa. Methods Water samples taken between May and August were analysed using the Colilert® system with Quanti-Tray®/2000 to quantify E. coli (most likely number per 100 mL), followed by PCR identification of virulence and ESBL genes (e.g., blaCTX-M, blaTEM, blaSHV) in isolates. Physicochemical characteristics were also measured, including temperature, pH, electrical conductivity, total dissolved solids, dissolved oxygen, and turbidity. Results and discussion Pathogenic E. coli was found in all seven rivers, with values typically over 1,286 MPN/100 mL and frequently surpassing 2419.6 MPN/100 mL (Colilert upper limit). All samples constituted a Very High Risk, according to WHO guidelines, and did not fulfil SANS 241 requirements for source and drinking water. Physicochemical studies showed seasonal hypoxia (DO down to 0.27 mg/L), near-neutral pH (6.46–7.95), and high EC/TDS (up to 557 μS/cm and 274 mg/L) in warmer times, often exceeding DWAF standards and suggesting wastewater contamination. The most prevalent pathotypes were EAEC (aggR; 71.4% of rivers), EPEC (bfpA; 67.9%), and EHEC (stx1/stx2; 57.1%). ESBL genes were common and commonly co-occurred with virulence genes in high-diversity rivers (e.g., Ngwedi, Tshinanne, Madadzhe, Luvuvhu). These findings reveal ongoing contamination with multidrug-resistant, diarrheagenic E. coli in Vhembe District’s wastewater-impacted rivers, which is exacerbated by poor water quality that supports microbial survival. This pollution exceeds national and international safety criteria, posing acute health concerns to local residents and hastening regional AMR spread.

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