Typing of intimin (eae) genes from enteropathogenic Escherichia coli (EPEC) isolated from children with diarrhoea in Montevideo, Uruguay: identification of two novel intimin variants (μB and ξR/β2B)

Abstract

A total of 71 enteropathogenic Escherichia coli (EPEC) strains isolated from children with diarrhoea in Montevideo, Uruguay, were characterized in this study. PCR showed that 57 isolates carried eae and bfp genes (typical EPEC strains), and 14 possessed only the eae gene (atypical EPEC strains). These EPEC strains belonged to 21 O : H serotypes, including eight novel serotypes not previously reported among human EPEC in other studies. However, 72 % belonged to only four serotypes: O55 : H− (six strains), O111 : H2 (13 strains), O111 : H− (14 strains) and O119 : H6 (18 strains). Nine intimin types, namely, α1 (two O142 strains), β1 (29 strains, including 13 O111 : H2 and 14 O111 : H−), γ1 (three O55 : H− strains), θ (five strains, including three strains with H40 antigen), κ (two strains), ε1 (one strain), λ (one strain), μB (six strains of serotypes O55 : H51 and O55 : H−) and ξR/β2B (22 strains, including 18 O119 : H6) were detected among the 71 EPEC strains. The authors have identified two novel intimin genes (μB and ξR/β2B) in typical EPEC strains of serotypes O55 : H51/H− and O119 : H6/H−. The complete nucleotide sequences of the novel μB and ξR/β2 variant genes were determined. PFGE typing after XbaI DNA digestion was performed on 44 representative EPEC strains. Genomic DNA fingerprinting revealed 44 distinct restriction patterns and the strains were clustered in 12 groups. Only 15 strains clustered in six groups of closely related (similarity >85 %) PFGE patterns, suggesting the prevailing clonal diversity among EPEC strains isolated from children with diarrhoea in Montevideo.