Concrement formation in the urinary bladder in rats inoculated with Ureaplasma urealyticum

To study the concrement-forming ability of Ureaplasma urealyticum in the urinary tract, viable and heat-killed ureaplasmas as well as urease and non-urease-producing bacteria were inoculated into the bladder in rats. Viable ureaplasmas, in contrast to heat-killed, caused the formation of bladder stones with a frequency corresponding to urease-producing bacteria (Proteus mirabilis). It was not possible to reculture the inoculated ureaplasmas from the urinary tract. Non-urease producing microorganisms (Escherichia coli and Mycoplasma hominis) only occasionally induced stone formation. The results indicate that U. urealyticum can initiate stone formation, a property that appears to be associated with the urease activity of the organism.