Abstract
Shiga toxin-producing Escherichia coli (STEC) causes a wide spectrum of diseases, including hemorrhagic colitis and hemolytic uremic syndrome (HUS). Almost 5% of STEC infections result from waterborne exposures, yet there is no test listed in the EPA’s current Selected Analytical Methods for the detection of active Shiga toxins (Stxs) in water. In this study, a HeLa cell-based assay is validated for the detection of metabolically active Stxs produced by STEC in water, including tap, bottled, and pond water. Active Stxs are detected even when the number of Stx-producing bacteria is less than 0.4 CFU/mL and the assay performance is not affected by background flora or chlorine in the water. This assay is not only as simple and affordable as cell-free assays but also detects active holotoxins without the use of live animals. In addition, the assay is designed for use in multi-well formats, making it ideal for high-throughput screening of water samples and therefore useful for environmental public health surveillance programs to reduce human risk of infection with STEC.
Highlights
From 2009 to 2017, 603 reported Shiga-toxin-producing Escherichia coli (STEC) outbreaks resulted in 7869 illnesses and 1404 hospitalizations [1]
Water mains can become exposed to STEC from damp soils near the site of repair or installation, whereas well water and aquifers can be contaminated by animal feces or sewage seepage [2,3,4,5,6]
We demonstrate a cell-based assay that is capable of detecting active Shiga toxins (Stxs) in water samples spiked with as few as 0.4 colony-forming units (CFU)/mL of STEC
Summary
From 2009 to 2017, 603 reported Shiga-toxin-producing Escherichia coli (STEC) outbreaks resulted in 7869 illnesses and 1404 hospitalizations [1]. The cell-free assays are easier, fast, and cheaper but only detect the enzymatic activity of the A-subunit of Stxs. They do not monitor the activity of the holotoxins [27,33,34]. We demonstrate a cell-based assay that is capable of detecting active Stxs in water samples spiked with as few as 0.4 colony-forming units (CFU)/mL of STEC. This cell-based assay eliminates the need for using live animals, allows high-throughput screening, and yields results in a short amount of time. The performance of the assay is not affected by either the presence of chlorine at the concentrations used to treat drinking water or the background flora present in environmental samples
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