Abstract
Safe water is a global concern, and methods to accurately monitor quality of water are vital. To assess the risks related to bacterial pathogen load in Lake Vomb that provides drinking water to the southern part of Sweden, this study combined molecular analyses of enterobacteria and bacterial pathogens in water using quantitiative real-time PCR with hydrodynamic modeling and quantitative microbial risk assessment (QMRA). A real-time PCR assay to detect enterobacteria was set up by primers targeting ssrA. Between February 2015 and May 2016, presence of ssrA gene copies as well as Campylobacter spp., Salmonella spp., and EHEC O157 DNA was analyzed by real-time PCR at several locations in the catchment of Lake Vomb and its tributaries Björkaån, Borstbäcken, and Torpsbäcken. Björkaån had the highest detected concentrations of the ssrA gene and, according to the results of hydrodynamic modeling, contributed most to the contamination of the water intake in the lake. None of the water samples were positive for genes encoding EHEC O157 and Campylobacter spp., while invA (Salmonella spp.) was present in 11 samples. The QMRA showed that the suggested acceptable risk level (daily probability of infection <2.7 × 10−7) is achieved with a 95% probability, if the Salmonella concentrations in the water intake are below 101 bacteria/100 mL. If a UV-disinfection step is installed, the Salmonella concentration at the water intake should not exceed 106 bacteria/100 mL.
Highlights
Public health risks associated with fecal contamination in recreational and drinking water are of global concern
Warmer temperatures have been associated with higher numbers of pathogenic bacteria as well as fecal indicator bacteria in water [43,44]
E. coli is higher in water during the warm-rainy season in areas with diarrheal epidemics [35,45], and the summer period in Sweden is often warm and dry, incidences [46] of food and water-borne bacterial infections in Sweden increase during summer periods
Summary
Public health risks associated with fecal contamination in recreational and drinking water are of global concern. Human or animal fecal contamination in water increases the risk of presence of pathogenic microorganisms, and a variety of illnesses have been associated with intake of, or exposure to, contaminated water, including gastrointestinal infections, skin-diseases, and eye and ear infections [1]. Many times caused by water-borne outbreaks, claim millions of lives annually [2]. Epidemiological studies worldwide have established links between gastrointestinal infections and exposure to contaminated water due to breakdown of the drinking water supply systems in poor. In most countries with developed water supply systems, increased levels of contamination are often linked to failures in water piping systems or drinking water treatment plants [5,6]. Storms and heavy rainfalls resulting in discharges of wastewater and runoff from livestock or wildlife into rivers and lakes can increase microbial contamination [7,8,9]
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