Various intensity of Proteus mirabilis-induced crystallization resulting from the changes in the mineral composition of urine.

Infectious urolithiasis is a result of recurrent and chronic urinary tract infections caused by urease-positive bacteria, especially Proteus mirabilis. The main role in the development of this kind of stones is played by bacterial factors such as urease and extracellular polysaccharides, but urinary tract environment also contributes to this process. We used an in vitro model to establish how the changes in the basic minerals concentrations affect the intensity of crystallization which occurs in urine. In each experiment crystallization was induced by an addition of P. mirabilis to artificial urine with a precisely defined chemical composition. Crystallization intensity was determined using the spectrophotometric microdilution method and the chemical composition of formed crystals was established by atomic absorption spectroscopy and colorimetric methods. Increasing the concentration of all crystals forming ions such as Mg(2+), Ca(2+) and phosphate strongly intensified the process of crystallization, whereas reducing the amount of these components below the proper physiological concentration did not affect its intensity. The inhibitory influence of citrate on calcium and magnesium phosphate crystallization and competitive actions of calcium and oxalate ions on struvite crystals formation were not confirmed. In the case of infectious stones the chemical composition of urine plays an important role, which creates a necessity to support the treatment by developing a model of proper diet.