Analysis of Pathogenicity Islands of STEC

In general, virulent bacteria are distinguished from nonvirulent ones by the presence of genes-encoding virulence factors. Virulence genes might be detected by polymeraase chain reaction (PCR) or hybridization, which also allows the identification of attenuated pathogenic strains. These might have lost not only one virulence gene but a whole set thereof that is part of a mobile genetic element.