Multilocus genotypic characterization of Escherichia coli O157:H7 recovered from food sources

Abstract

Escherichia coli O157:H7 strains (n = 33) recovered from different food sources in Egypt were characterized using molecular assays to identify strain genotypes associated with various levels of pathogenic potential. Genotypic characterization included: lineage-specific polymorphism assay (LSPA-6), Shiga-toxin-encoding bacteriophage insertion site assay (SBI), clade 8 typing, Tir (A255 T) polymorphism, and variant analysis of Shiga toxin 2 gene (Stx2a and Stx2c), and anti-terminator Q genes (Q933 and Q21). Genotypes LI/II (76%), SBI 1 (60·6%), clade 8 (69·7%), Tir (255 T) (72·7%) and Stx2c (45·5%) were found to be significantly more frequent compared to other genetic markers in the strains analysed. Multivariable analysis revealed a significant association between LPSA-6 and clade types as well as Tir (A255 T). To the best of our knowledge, this is the first study to report the characterization of these genetic markers in E. coli O157:H7 strains in the Middle East and Africa.