Adherence of Escherichia coli to Human Urinary Tract Epithelial Cells

Abstract

The adherence of Escherichia coli to human uroepithelial cells obtained from midstream urine specimens of healthy women was studied. Bacteria labeled with [³H]uridine were used, and unattached organisms were separated from the epithelial cells by vacuum filtration with 5-μm-pore-size Nucleopore membrane filters. These techniques allowed adherence to be measured in large numbers of epithelial cells and overcame the problem of distinguishing experimental bacteria from the indigenous organisms present on uroepithelial cells. Adherence was not appreciably affected by temperature. Adherence was maximal at pH 4 to 5 and at bacterial-to-epithelial-cell ratios of 5,000 or more. The latter observation suggested that there are a limited number of receptors on the epithelial cell surface, an idea which was supported by competition experiments. Adherence occurred within 1 min and then decreased gradually or quickly, depending on the type of bacterial growth medium, to a stationary level of adherence, approximately 50% of that observed initially. The ability of epithelial cells from a single individual to bind E. coli varied in a cyclical and repetitive pattern. Adherence tended to be higher during the early phase of the menstrual cycle and diminished shortly after the time of expected ovulation; adherence frequently correlated with the value obtained on the same day of the menstrual cycle during the preceding months. Adherence was markedly enhanced by bacterial incubation in broth for 72 h and inhibited by α-d-mannose. These results suggest that adherence is a complex phenomenon perhaps mediated in part by bacterial pili and mannose residues on uroepithelial cells.