Abstract
Salmonella spp. is associated with fecal pollution and capable of surviving for long periods in aquatic environments. Instead of the traditional, time-consuming biochemical detection, polymerase chain reaction (PCR) allows rapid identification of Salmonella directly concentrated from water samples. However, prevalence of Salmonella may be underestimated because of the vulnerability of PCR to various environmental chemicals like humic acid, compounded by the fact that various DNA polymerases have different susceptibility to humic acid. Because immunomagnetic separation (IMS) theoretically could isolate Salmonella from other microbes and facilitate removal of aquatic PCR inhibitors of different sizes, this study aims to compare the efficiency of conventional PCR combined with immunomagnetic separation (IMS) for Salmonella detection within a moderately polluted watershed. In our study, the positive rate was increased from 17.6% to 47% with nearly ten-fold improvement in the detection limit. These results suggest the sensitivity of Salmonella detection could be enhanced by IMS, particularly in low quality surface waters. Due to its effects on clearance of aquatic pollutants, IMS may be suitable for most DNA polymerases for Salmonella detection.
Highlights
Belonging to Enterobacteriaceae, Salmonella is a rod-shaped, Gram-negative bacterium
Because water containing pollution from many sources could contain polymerase chain reaction (PCR) inhibitors of various kinds such as organic compounds, heavy metals, and humic acids, and various commercial DNA polymerases have different vulnerability, pretesting the reaction efficiency may be required before detection of environmental pathogens [13]
To facilitate detection of water pathogens independent of the polymerases used, we examined whether immunomagnetic separation (IMS) could improve the detection of Salmonella by the cheaper, highly accessible conventional PCR
Summary
Belonging to Enterobacteriaceae, Salmonella is a rod-shaped, Gram-negative bacterium. Many serotypes of Salmonella are known gastrointestinal pathogens, with some capable of causing illness in humans and other mammals with as few as 10 to 1000 organisms [1]. Contaminated foods and water are two critical infection routes for Salmonella. Outbreaks are frequent around the world, especially in countries with poor sanitary conditions [2]. In advanced countries like the United States, there are approximately 42,000 cases of non-typhoidal Salmonella infection each year [3]. Because of their strong pathogenicity and endurance in aquatic environments, epidemic strains of Salmonella are of considerable concern for public health [4,5]
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