Induction of crystal formation in artificial urine by Proteus mirabilis isolated from kidney stone patients

Abstract

Escherichia coli and Proteus mirabilis are the common bacteria found in kidney stone and urine of the stone formers in northeast Thailand. They may play role in crystallization and stone formation. We therefore evaluated the induction of crystal formation in artificial urine by bacteria isolated from kidney stone and urine of the kidney stone patients, including E. coli (non urease-producing Gram negative bacteria) and P. mirabilis (urease-producing Gram negative bacteria). Induction of crystal and pH in artificial urine were investigated under inverted microscopy and pH meter, respectively after cultured at 25 °C for 0, 6, 12, 24, 48 and 72 hours. The chemical compositions of crystals were also identified by Fourier-transformed infrared (FTIR) spectroscopy. The results showed that E. coli was unable to induce crystal within72 hours but the urinary pH was in creased from 5.8 ± 0.0 to 7.0± 0.0. However, P. mirabilis was able to induce dendritic crystals at 12 hours (pH = 9.0 ± 0.0) and the number of crystals was increased to 21 ± 5, 73 ± 13, > 100 and >100 crystals/well at 12, 24, 48 and 72 hours, respectively. The shapes of these crystals were observed in both forms of dendrite and dendritic branches at 24, 48 and 72 hours. FTIR technique revealed that the chemical compositions of crystals were magnesium ammonium phosphate. In conclusion, our results indicated that urease produced by P. mirabilis isolated from kidney stone and urine was an important factor which could induce the formation of magnesium ammonium phosphatecrystals in artificial urine. Further investigation for the other possible mechanisms of stone genesis by these causative bacteria is required.