Characterization of six Shiga toxin-producing Escherichia coli (STEC) strains carrying Stx2-phages from Colombia

Shiga toxin producing Escherichia coli (STEC) is a bacterial pathogen that causes diarrhea and severe human diseases like HUS; its main virulence factor are the Shiga toxins (Stx1 and Stx2). Some Stx2 subtypes have been identified and associated with the risk of developing severe illness. Stx toxins are encoded in temperate bacteriophages which control their expression through the lytic cycle that is regulated by the late genes and Q anti-terminator protein. The aim of this work was to characterize six STEC strains carrying Stx2-phages to provide preliminary information and understanding about Stx2 strains from Colombia regarding the Stx production, lytic cycle induction and subtyping of Stx2. Two highlighted strains with higher levels of Stx production and lytic cycle’s induction were observed. All the evaluated strains carried either the Stx2a, Stx2c, or Stx2d subtypes. In addition, most of the strains carried the qO111 allele, and only one strain showed differences in the ninG region. Differences in the evaluated characteristics of the strains were observed, which could indicate the variability of these six STEC strains carrying Stx2-phages.