Experimental production of bladder calculi in rats by ureaplasma injection.

Certain infection stones are thought to be linked to urease-possessing bacteria such as Proteus sp. Since ureaplasma also contain urease and are predominantly located in the urogenital tract, their possible role in the formation of infection stones was studied in the rat model described by Friedlander and Braude [2]. Infection stones were produced in Sprague-Dawley and Wistar male rats after injection of ureaplasmas into the renal medulla. In Sprague-Dawley rats, six different ureaplasma strains (serotypes 3 and 5 clinical isolates) were able to produce bladder stones. Acetohydroxamic acid, a urease inhibitor, prevented the formation of the stones. There was no difference in urinary pH or the presence of leukocytes, crystals and ureaplasmas in the urine between rats which presented stones and those which did not. Ureaplasmas could be cultivated only very rarely from rat stones. Similarly, no ureaplasmas could be obtained from human stones.