Abstract
Shiga toxin (Stx), one of the most potent bacterial toxins known, can cause bloody diarrhea, hemolytic uremic syndrome, kidney failure and death. The aim of this pilot was to investigate the occurrence of Shiga toxin-encoding genes, stx (stx1 and stx2) from total coliform (TC) and E. coli positive samples from small community water systems. After aliquots for TC and E. coli analyses were removed, the remnant volume of the samples was enriched, following a protocol developed for this study. Fifty-two per cent of the samples tested by multiplex PCR were positive for the presence of the stx genes; this percentage was higher in raw water samples. The stx2 gene was more abundant. Testing larger volumes of the samples increase the sensitivity of our assay, providing an alternative protocol for the detection of Shiga toxin-producing E. coli (STEC) that might be missed by the TC assay. This study confirms the presence of Stx encoding genes in source and distributed water for all systems sampled and suggests STEC as a potential health risk in small systems.
Highlights
Shiga toxin (Stx), produced by some serotypes of E. coli belonging to the enterohemorrhagic E. coli (EHEC) pathotype (Nataro & Kaper ), is one of the most potent bacterial toxins known
In the United States (USA) alone, it is estimated that Shiga toxin-producing E. coli (STEC) causes more than 265,000 infections, 3,600 hospitalizations and 30 deaths annually (CDC )
Total and free chlorine was Enumeration to log density was done by presence–absence (PA) in serial decimal dilutions for total coliforms (TC), and E. coli following an amendment of the Standard Methods protocol for the detection of TC
Summary
Shiga toxin (Stx), produced by some serotypes of E. coli belonging to the enterohemorrhagic E. coli (EHEC) pathotype (Nataro & Kaper ), is one of the most potent bacterial toxins known. In the United States (USA) alone, it is estimated that Shiga toxin-producing E. coli (STEC) causes more than 265,000 infections, 3,600 hospitalizations and 30 deaths annually (CDC ). The virulence of STEC strains is associated with the activity of the toxins encoded by Stx-converting phages (Schmidt ), which are mobile elements involved in the transfer of genes from one host to another. STEC is mostly associated with foodborne illness but STEC has been documented as the causative agent of important waterborne outbreaks in Japan, in Fife, Scotland and in Canada. In the USA, major outbreaks have been reported in Missouri, Wyoming and New York
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