ACTIN ACCUMULATION ASSOCIATED WITH CLUSTERED AND LOCALIZED ADHERENCE IN ESCHERICHIA-COLI ISOLATED FROM PATIENTS WITH DIARRHEA

Escherichia coli D2 (serotype 07:H-) that was isolated from a child wi th diarrhea hybridized with an F1845 DNA probe used to detect diffuse adherence. Strain D2 adhered to tissue culture cells (HeLa and HEp-2 c ells) in a clustered pattern but did not autoagglutinate on the cell s urface and induced the elongation of microvilli after 3 h of incubatio n. After 6 h of incubation, the infected cells were positive for fluor escent-actin staining at the site of clustered adherence. When analyze d with a confocal laser scanning microscope, each D2 cell was surround ed by accumulated actin in a capsule-like formation. Capsule-like, acc umulated actin was also observed with enteropathogenic E. coli (EPEC), although in this case, actin accumulation was associated with EPEC mi crocolonies in a localized pattern. Four other strains of F1845 DNA pr obe-positive, diffusely adhering E. Coli were negative for actin accum ulation. Strain D2 did not hybridize with EPEC attaching and effacing DNA or EPEC adherence factor DNA probes. In addition, clustered D2 cel ls were found inside tissue culture cells. The data suggest a novel in fectious mechanism as well as genetic heterogeneity of F1845 DNA probe -positive E. coli, Capsule like, accumulated actin may protect the bac teria from host defense mechanisms.