R factor-mediated adhesiveness to mammalian cells in E. coli K12

We checked the possible effects of the standard plasmids of known compatibility groups on the ability of three strains of E. coli K12, J62, J53 and C600, to agglutinate human and guinea pig erythrocytes and to adhere to cultures of human epithelial cells. The results obtained showed that under defined experimental conditions one plasmid, R478, from a clinical isolate of Serratia marcescens is able to modulate the adhesive properties of the strain J62 which lacks adhesiveness. On the contrary, the same factor did not alter the ability of strains J53 and C600 to agglutinate erythrocytes and to adhere to human epithelial cells in culture, nor did it induce adhesive properties in wild-type strains of E. coli from clinical isolates that lacked them. This would suggest a possible plasmidic control of chromosomally encoded surface structures that mediated adhesiveness of E. coli to mammalian cells.