Bacterial adhesion to uroepithelial cells: a morphologic study.

Urethral and midstream urine samples from healthy women and from patients with urinary tract infections (UTI) were examined by electron microscopy. Urethral urine samples from healthy subjects contained sparsely and densely colonized uroepithelial cells. The latter had morphologically heterogeneous bacteria adherent to each other and to the epithelial cell by a ruthenium red-positive fibrous matrix, which was present on the surface of all bacteria examined. Urethral urine samples from patients with UTI often had two distinct microcolonies of morphologically similar bacteria adherent to the same uroepithelial cell. Midstream urine samples from these patients contained large microcolonies of morphologically identical bacteria. Urine from patients with catheter-associated infections contained few uroepithelial cells and two distinct varieties of bacterial microcolonies--one of intact homogeneous cells and another of a mixture of damaged and intact bacteria. These in vivo observations indicate that the bacterial surface matrix participates in bacterial adhesion to uroepithelial cells and in bacteria-bacteria adhesion.