PREVALENCE OF tccP AND tccP2 GENES IN CLINICAL ATYPICAL ENTEROPATHOGENIC Escherichia coli ISOLATES

Atypical enteropathogenic Escherichia coli (aEPEC) is an important etiological agent of infantile diarrhea worldwide. Pathogenic aEPEC strains employ LEE-encoded proteins to subvert normal host cell functions, culminating in intestinal pathologic alterations termed attaching and effacing (A/E) lesions. In addition, some aEPEC strains harbor non-LEE effectors that may contribute to pathogenesis, such as Tir-cytoskeleton Coupling Protein (TccP/TccP2 also named EspFu), which is involved in the formation of A/E lesions and intestinal colonization. However, there are few studies regarding the frequency of tccP/tccP2 genes in clinical aEPEC isolates. Here we examined a total of 72 aEPEC strains isolated during an epidemiological study of the etiology of acute diarrhea in Salvador, Brazil. The presence of tccP and tccP2 genes was investigated by polymerase chain reaction (PCR). The positive isolates were further screened using the new Clermont phylotyping method, in order to assess the impact of the phylogeny on presence of these genes in aEPEC. The tccP and/or tccP2 genes were detected in 31 (43%) isolates, which belonged to 21 O:H serotypes and harbored eight intimin subtypes. A significant association was observed between the presence of tccP/tccP2 genes and the presence of epsilon-intimin (p<0.005) or the ONT:H19 serotype (p<0.05). Seven isolates carried tccP, 23 harbored tccP2, and one was positive for both genes. All O55:H7 and O111:H38 isolates tested were positive for tccP and tccP2 genes, respectively. The tccP-carrying isolates were assigned to E (five), A (one) and B2 (one) phylogroups, while the tccP2-positive ones fall into B1 (17) and A (four). Two tccP2-postive isolates could not be classified according to the phylotyping method used. Interestingly, an O55:H7 isolate harboring both tccP and tccP2 genes was assigned to A phylogroup, while those tccP-positive belonged to E, indicating distinct phylogenetic lineages within O55:H7 serotype. In conclusion, tccP/tccP2 genes are widely distributed in clinical aEPEC isolates, with predominance of the tccP2 allele. Moreover, tccP seems to be related to strains belonging to E group, particularly O55:H7, whereas tccP2 is more associated with B1 strains from several serotypes, suggesting a phylogenetic distribution of these genes among pathogenic aEPEC.