HELA-CELL INVASION BY A STRAIN OF ENTEROPATHOGENIC ESCHERICHIA-COLI THAT LACKS THE O-ANTIGENIC POLYSACCHARIDE

The interaction with HeLa cells of an enteropathogenic Escherichia coli (EPEC) strain and its plasmid‐cured derivative strain was examined. An O111:NM EPEC strain B171 harbours a 54 megadalton plasmid (pYR111) necessary for the expression of both localized adherence (LA) to HeLa cells and the 0‐repeating side chain of the lipopolysaccharide. Under light microscopy, the plasmid‐cured derivative strain B171‐4 was observed to interact with HeLa cells in a pattern distinct from LA. Transmission electron microscopy showed that the bacteria were internalized by HeLa cells. In contrast, strain B171 induced pedestal‐like projections and invaginations of the plasma membrane, but was never completely internalized. A quantitative assay to determine the number of internalized bacteria revealed that strain B171‐4 was internalized at levels 30–70‐fold higher than those of aviruient E. coli strains. Cytochalasin B reduced the levels of internalization of both strain B171‐4 and an entero‐invasive E. coli strain (E11), but did not affect LA by strain B171. These results suggest that EPEC strain B171 may carry a specific chromosomally determined surface factor needed to initiate internalization by HeLa cells. However, a plasmid‐determined factor alters the nature of this interaction; the combined effects of the chromosomal and plasmid determinants lead to the characteristic attachment of the bacteria in clusters on the surface of the eukaryotic cell. Copyright © 1990, Wiley Blackwell. All rights reserved