Shiga toxin-producing Escherichia coli (STEC) from Humans in the Netherlands: Novel diagnostic approach, molecular characterization and phylogenetic background

The shiga toxin-producing Escherichia coli (STEC) bacterium poses a serious public health risk as it can cause life threatening condition hemorrhagic colitis and hemolytic uremic syndrome besides diarrhea. STEC is associated with several food related outbreaks worldwide, including the famous one in Germany in 2011. We used rapid molecular diagnostics, including sequencing of the whole bacterial genome, to reveal the public health risks of STEC circulating in the Netherlands by determining virulence and antibiotic resistance, and other molecular properties of STEC isolated from Dutch patients. No correlation was found between the severity of the disease and specific types of STEC. Our results showed that STEC may originate from different kinds of E. coli, including the ones found in normal human and animal gut flora, by acquiring the Shiga toxin (Stx) encoding bacteriophage. We also proved that some stx negative E. coli types, but carrying other virulence genes of STEC, are in fact members of STEC although they are not diagnosed as such. Either they have lost the Stx bacteriophage or could be progenitor of STEC being prepared to acquire the phage. We also diagnosed patients with an STEC type, very similar to the 2011 German outbreak one. Furthermore, we showed that, although some specific types of STEC are known to cause outbreaks, none of the other types should be neglected as they may evolve into a new pathogenic clone. Therefore, obtaining more knowledge on and surveillance of STEC is essential to prevent future outbreaks, and modern molecular methods are powerful tools to achieve this.