Purpose: This study aimed to characterize 82 atypical enteropathogenic Escherichia coli (aEPEC) isolates, obtained from patients with diarrhea in Brazil, regarding their adherence patterns on HeLa cells and attaching and effacing (AE) lesion pathways.
Methodology: The adherence and fluorescence-actin staining (FAS) assays were performed using HeLa cells. AE lesion pathways were determined through the detection of tyrosine residue 474 (Y474) phosphorylation in the Tir protein, after its translocation to host cells, and by PCR assays for tir genotyping and detection of Tir-cytoskeleton coupling protein (tccP) genes.
Results: Regarding the adherence pattern, determined in the presence of d-mannose, 12 isolates (14.6 %) showed the localized adherence (LA)-like pattern, 3 (3.7 %) the aggregative adherence pattern and 4 (4.9 %) a hybrid LA/diffuse adherence pattern. In addition, 36 (43.9 %) isolates displayed an undefined adherence, and 26 (31.7 %) were non-adherent (NA), while one (1.2 %) caused cell detachment. Among the 26 NA aEPEC isolates, 11 showed a type 1 pilus-dependent adherence in assays performed without d-mannose, while 15 remained NA. Forty-eight (58.5 %) aEPEC were able to trigger F-actin accumulation underneath adherent bacteria (FAS-positive), which is an important feature of AE lesions. The majority (58.3 %) of these used the Tir-Nck pathway, while 39.6 % may use both Tir-Nck and Tir-TccP pathways to induce AE lesions.
Conclusion: Our results reveal the diversity of strategies used by aEPEC isolates to interact with and damage epithelial host cells, thereby causing diarrheal diseases.
Keywords: adherence; attaching and effacing lesion; atypical EPEC and pathogenicity; diarrhea.