In vitro attachment to a human cell line of Escherichia coli strains causing urinary-tract infection: occurrence of fimbriae (pili) in adhesive and non-adhesive strains.

In this study, 20 strains of Escherichia coli isolated from infected urinary-tract were screened for the occurrence of haemagglutinating (HA) activity and for the possible relationship between a fimbriate surface structure and adhesion ability to the surface of a human cell line. Only 8 of the 20 adhesive strains agglutinated human or guinea-pig erythrocytes or both. In 7 of the 8 strains, the haemagglutinating activity with human erythrocytes was D-mannose-resistant; one strain was D-mannose-sensitive with guinea-pig red blood cells (RBC). In 40 non-adhering E. coli isolated from urine, D-mannose-resistant HA was rarely detected; in contrast, agglutination of guinea-pig was more frequent and D-mannose-sensitive when it occurred. No correlation was found between the degree of HA activity and the ability to adhere. Moreover at low growth temperature (18 degrees c), haemagglutinin was absent in all the strains tested, whereas residual adhesion capacity could be detected in some strains. Similar results were recorded after heating the bacterial suspension at 65 degrees C. Generally pili detected by electron microscopy were present at the surface of the strains which agglutinated RBC. There is no correlation between the presence of fimbriae or pili and adhesion of E. coli to the human cell line used in this study. A range of distinct mechanisms of E. coli adhesion appeared to be involved in the phenomenon described in this report.