Water quality and diarrhoeagenic Escherichia coli detection in surface Pampean aquatic systems

Abstract

Many surface water systems are impacted by point source pollution from sewage discharges and industrial wastes, as well asdifuse pollution from agriculture and livestock farming, inducing a potential biohazard to human, animal, and environmentalhealth. This study aimed to determine the presence of diarrhoeagenic Escherichia coli (DEC) pathotypes and their antibioticresistance, as well as the bacteriological, physical, and chemical water quality conditions in two Pampean peri-urban rivers(Rojas and Salado rivers, Buenos Aires, Argentina) used for recreation. Additionally, we explored the impact of the surroundingland use on the water quality. In the Rojas (R) and Salado (S) rivers, wastewater discharges from treatment plants increasednutrient content and coliform abundances at specifc sampling sites (R2 and S3) and downstream (R3 and S4, respectively).Coliform abundances correlated with ammoniacal nitrogen concentrations, both exceeding recreational use guidelines. Outof 36 samples positive for DEC virulence factors, 11 DEC strains were isolated (5 enteroaggregative, 3 enteropathogenic, 1shigatoxigenic-stx1/stx2, 1 shigatoxigenic-stx2, 1 hybrid enteroaggregative-enterotoxigenic). Six strains were resistant to oneor more antibiotics. Our results suggest that diferences in E. coli pathotypes between the two rivers and the water quality ofeach sampling site are linked to the surrounding land use, evidencing both difuse and point source pollution.