Assessing the groundwater quality at a Saudi Arabian agricultural site and the occurrence of antibiotic-resistant opportunistic pathogens on irrigated food produce. Groundwater quality and food safety

This study monitors the groundwater in wells situated near to agricultural fields of Saudi Arabia. Vegetables irrigated with the groundwater were also assessed for their microbial safety. The amount of total nitrogen exceeded the 15 mg/L permissible for agricultural irrigation in most of the sampled groundwater. Fecal coliforms in density >12 MPN/100 mL were detected in some of the groundwater wells of close proximity to a chicken farm. Coupled with qPCR-based fecal source tracking, monitoring effort showed that groundwater in two of the wells nearest to the chicken farm were relatively more perturbed than the other wells. Anthropogenic contamination resulted in a shift of predominant bacterial phylum within the groundwater microbial communities. Specifically, there was an elevated presence of Proteobacteria but a lower microbial richness in the groundwater perturbed by anthropogenic contamination. Acinetobacter was detected at high relative abundance of up to 48.6% in the total microbial community of groundwater but culture-based analysis did not recover any antibiotic-resistant bacteria and opportunistic pathogens from the groundwater. Although Enterococcus faecalis and Pseudomonas aeruginosa were isolated from the vegetables irrigated with the groundwater, quantitative microbial risk assessment suggests that the annual risk incurred from consumption of these vegetables are within the acceptable limits of 10-4. Our findings highlighted that the groundwater quality at this agricultural site in the western Saudi Arabia was not as pristine as commonly perceived. Despite the poor groundwater quality, there was no significant impairment of food quality arising from the groundwater.