SECRETED AUTOTRANPORTER TOXIN (SAT) IN ATYPICAL ENTEROPATHOGENIC ESCHERICHIA COLI (AEPEC)

Keyde Cristina Martins de Melo (IBU); Taisy Renata Mazur (IBU); Elisabete Silva Soares (IBU); Rita de Cássia Ruiz (IBU)

Introduction: E. coli strains associated with the human host are classified as commensals, enteric pathogens or extraintestinal pathogens. These differences depend on the set of virulence genes and clinical properties of each pathotype. Enteropathogenic Escherichia coli (EPEC) constitutes one of the six diarrheagenic E. coli categories, which was divided into two groups, typical EPEC and atypical EPEC, whose basic difference (as compared to tEPEC) is the absence of the EPEC adherence factor plasmid (pEAF), and wider heterogeneity of virulence factors. The diffusely adhering E. coli (DAEC) is one of the human pathogenic E. coli strains responsible for recurrent urinary tract and gastrointestinal infections. Studies have shown that some DAEC strains harbor virulence factors found in uropathogenic E.coli (UPEC) strains, such as the secreted autotransporter toxin, Sat. Sat belongs to the subfamily of serine protease autotransporters of Enterobacteriaceae. This family, which has a specific and distinct function, has been indentified only in pathogenic bacteria. Objective: To investigate Sat toxin expression in isolates of aEPEC, whose gene sat was amplified by multiplex PCP Methods: Cytotoxicity assays in HEp-2 cells were performed with the bacterial culture or supernadant of the culture from isolates 589 (O5:H2) sat/pic/east; 1887 (O111:H38) sat/hly; 2294 (O9:H33) east/sat  and 3170 (O145:H2) PCR negative.  Results and Discussion: Our results show that isolates positive for the sat gene were unable to produce cellular alterations in HEp-2 cell cultures. On the other hand, cells incubated with the concentrated supernatant from bacterial cultures (50 e 100 µg/mL), containing only molecules over 50 kDa, showed high levels of vacuolization, after 5 h of incubation. A partial cell detachment was only detected in cultures incubated with concentration of 250 µg/mL, for 24 h. These results suggest for the first time that aEPEC may express the Sat toxin, important for infection by both UPEC and DAEC. The study of the expression and activity of bacterial toxins is of primordial importance for the understanding of the pathogenesis of the bacterial infections. In particular, the founding of the expression of the Sat toxin in aEPEC will certainly contribute with the understanding of pathogenesis of infections by this class of E. coli, still very poorly known.