The role of plasmids in adherence of invasive Escherichia coli to mammalian cells.

Strains of Escherichia coli isolated from persons with dysentery-like diarrheal disease were demonstrated to adhere to the surface of cultured HEp-2 (human epithelial) cells under conditions that removed nonpathogenic control bacteria and to cause hemagglutination of human red blood cells. The plasmid content of 13 stains surveyed was found to be variable with respect to resistance to antibiotics and the presence of small cryptic plasmids. Conjugal transfer to resistance plasmids from two of the clinical isolates to a number of nonpathogenic laboratory and field isolates of E. coli was not accompanied by transfer of the capacity either for specific interaction with cultured HEp-2 cells or for hemagglutination of human red blood cells. Furthermore, cured derivatives of the enteroinvasive strains retained positive reactions in the assay systems.