Detection and identification by PCR of a highly virulent phylogenetic subgroup among extraintestinal pathogenic Escherichia coli B2 strains

Abstract

Closely related Escherichia coli B2 strains O1:K1, O2:K1, O18:K1, and O45:K1 constitute a major subgroup causing extraintestinal infections. A DNA pathoarray analysis was used to develop a PCR specific for this subgroup that was included in the multiplex phylogenetic-grouping PCR method. Our PCR may serve to identify this virulent subgroup among different ecological niches.

FIG. 1.

(A) Pentaplex PCR combining the amplification of a 434-bp fragment of the svg ORF specific for highly virulent B2₁/ST29 E. coli strains; uidA (β-glucuronidase gene) was used as a control (16), and chuA (outer membrane hemin receptor gene) and yjaA (unknown function) and DNA fragment TspE4.C2 were used for phylogenetic group affiliation (12). M, molecular weight marker (100-bp DNA ladder; New England BioLabs); lanes 1, 2 and 3, strains belonging to phylogenetic groups A, B1, and D, respectively; lane 4, reference strain belonging to the phylogenetic group B2 but not to B2₁/ST29 (strain CFT073); lane 5, meningitis strain belonging to B2₁/ST29 (strain S88). (B) Biplex PCR combining the amplification of a 434-bp fragment of ORF svg (upper band) together with uidA (β-glucuronidase gene, lower band), used as a control (16), for the detection of highly virulent B2₁/ST29 E. coli strains directly in stool samples. Lanes 1 and 3, stool samples harboring B2₁/ST29 E. coli strains (svg-positive PCR); lane 2 and 4, stool samples harboring E. coli strains not belonging to B2₁/ST29 subgroup; lane 5, negative control.