Molecular Characterisation of Escherichia coli Collected From an Urban River in Johannesburg, South Africa.

Diarrheal diseases remain a significant public health concern worldwide, particularly among children under five. Surveillance is primarily focused on clinical samples. However, environmental reservoirs, particularly rivers, are increasingly recognised as critical sources of enteric pathogens. This study used whole-genome sequencing (WGS) to characterise Escherichia coli isolates from the Jukskei River in Johannesburg, South Africa. Twenty-seven E. coli isolates were subjected to pathotype-specific PCR and WGS for characterisation. Diarrheagenic E. coli accounted for 44% (12/27) of the isolates, including enterotoxigenic, atypical enteropathogenic and a hybrid enterotoxigenic-enteroinvasive E. coli. Most isolates (63%, 17/27) were O16:H48, and fimbrial typing revealed nine Fimtypes, with fimH27 being the most prevalent at 56% (15/27). Resistance to ciprofloxacin, sulfamethoxazole and azithromycin was noted in 11% (3/27) of the isolates. The most prevalent virulence-associated genes were fimH, csgA, gad, terC, ompT, iss and yehA-D, associated with adhesion, invasion and stress response. Phylogroup A dominated the collection (70%, 19/27), and phylogenetic analysis revealed diversity among the river isolates. Some genetic links between human and livestock strains were noted, suggesting cross-environmental transmission. These findings highlight the Jukskei River as a potential vehicle for E. coli transmission and underscore the importance of integrated surveillance across the environmental, human and animal sectors.