Assessing microbial risks of Escherichia coli: A spatial and temporal study of virulence and resistance genes in surface water in resource-limited regions

Abstract

Environmental microbial pollution can potentially cause illnesses and deaths among human populations. Environmental factors such as geomorphology, land use, human activities, and seasonality could influence pathogen dissemination. This study performed a space-temporal analysis of Escherichia coli concentrations, virulence (eaeA, bfpA, stx2, aatA, and st), and resistance (tetA, blaTEM, blaOXA, Intl-1, Intl-2, sul-1, and sul-2) genes in surface water within the Virilla sub-watershed, Costa Rica. The research employs microbiological, geostatistical, and quantitative microbial risk assessment (QMRA) techniques to evaluate the health risks associated with diarrheagenic E. coli. Samples collected monthly over a year were analyzed for fecal coliforms, E. coli, Enterococcus faecalis, physicochemical parameters, and the presence of virulence and resistance genes. The geographically weighted regression model identified significant associations between the virulence and resistance genes presence and environmental factors influence such as land use, slope, altitude, and seasonal changes. The results show that urban and grazing land use significantly influence the presence of resistance genes, while human fecal pollution is associated with higher concentrations of virulence genes. Seasonal variations showed that wet seasons contributed to increased gene presence (number of positive samples) and diversity (variety of virulence and resistance genes) compared with dry season. The QMRA results indicated that the total health disease burden was higher than the benchmark for drinking water recommended by WHO (1.00 × 10-6 DALY - Disability-Adjusted Life Years - per person per year) by between one and four magnitudes orders, particularly in regions with urban and grazing land use, human fecal pollution class, and lower altitudes. This study highlights the relevance of integrating environmental and microbial data to enhance water quality management and public health strategies in resource-limited regions. It underscores the need for targeted interventions, such as improved wastewater treatment and establishing buffer zones, to mitigate the risks associated with microbial pollution in surface waters.