Application of an improved methodology to demonstrate bacterial adherence during the menstrual cycle

We studied bacterial adherence to uroepithelial cells of female patients in relation to the menstrual cycle. We determined the number of bacteria demonstrable on native cells and the number of adhering bacteria after incubation with E. coli. Free bacteria and uroepithelial cells with adhering bacteria were optimally separated by differential centrifugation using sodium metrizoate (9.6%) and dextran (5.6%) (Lymphoprep). Thus, contamination of the cell preparation by free (non-adhering) bacteria was avoided and results were well reproducible. A median of five bacteria/cell (range 0-19) was observed for uroepithelial cells obtained from urine of female patients. Such bacteria were mostly rods. After in vitro incubation with E. coli cultures, a median of 33 bacteria/cell (range 17-54) was counted. Our improved methodology failed to demonstrate a relationship between bacterial adhesion and the menstrual cycle.