Atypical enteropathogenic Escherichia coli (aEPEC) is a significant cause of diarrhea in developing countries. Some aEPEC strains, including the Brazilian representative strain of serotype O51:H40 called aEPEC 1711-4, can use flagella to attach to, invade, and persist in T84 and Caco-2 intestinal cells. They can even translocate from the gut to extraintestinal sites in a rat model. Although various aspects of the virulence of this strain were studied and the requirement of the T3SS for the efficiency of the invasion process was demonstrated, the expression of the LEE genes during the invasion and intracellular persistence remains unclear. To address this, the expression of flagella and the different LEE operons was evaluated during kinetic experiments of the interaction of aEPEC 1711-4 with enterocytes in vitro. The genome of the strain was also sequenced. The results showed that flagella expression remained unchanged, but the expression of eae and escJ increased during the early interaction and invasion of aEPEC 1711-4 into Caco-2 cells, and there was no change 24 hours post-infection during the persistence period. The number of pedestal-like structures formed on HeLa cells also increased during the 24-hour analysis. No known gene related to the invasion process was identified in the genome of aEPEC 1711-4, which was shown to belong to the global EPEC lineage 10. These findings suggest that LEE components and the intimate adherence promoted by intimin are necessary for the invasion and persistence of aEPEC 1711-4, but the detailed mechanism needs further study.
Keywords: LEE; aEPEC; complete genome; enteropathogenic Escherichia coli; gene expression; intracellular persistence; invasion.