The antibacterial effect of the bladder surface: an electron microscopic study.

To explore an intrinsic bladder defense mechanism we examined interaction between Escherichia coli and bacterial size particles (polystyrene latex balls) and the vesical luminal surface by scanning and transmission electron microscopy. The bacteria and the latex spheres were held in folds of the cellular luminal surface. Voiding (bladder contraction) resulted in the entrapment of a large number of bacteria and particles by these microplicae, with their apparent engulfment in vesicles below the cell surface. Some urine was probably contained in the folds and vesicles, thus reducing the volume of residual urine in the bladder. Since leukocytes were rarely seen in the model studied they presumably do not play an immediate role against acute infection in the normal bladder. These observations indicate that fixation of bacteria to the mucosa is 1 step in the mechanism whereby the normally functioning bladder resists infection.