Influence of chondroitin sulfate, heparin sulfate, and citrate on Proteus mirabilis-induced struvite crystallization in vitro

Abstract

Struvite crystals were produced by Proteus mirabilis growth in artificial urine, in the presence of a number of naturally occurring crystallization inhibitors. The use of phase contrast light microscopy enabled the effects of added chondroitin sulfate A, chondroitin sulfate C, heparin sulfate, or sodium citrate, on struvite crystal growth rates to be rapidly monitored as changes in crystal habit. Struvite crystals formed as a consequence of the urease activity of P. mirabilis under all chemical conditions. In the absence of inhibitor, early crystal development was marked by large quantities of amorphous precipitate, followed immediately by the appearance of rapidly growing X-shaped or planar crystals. Addition of the glycosaminoglycans, chondroitin sulfate A, chondroitin sulfate C, or heparin sulfate to the artificial urine mixture had no effect on the rate of crystal growth or appearance. When sodium citrate was present in elevated concentrations, crystal appearance was generally slowed, and the crystals assumed an octahedral, slow growing appearance. None of the added compounds had any influence on bacterial viability, pH, or urease activity. It is therefore likely that the inhibitory activity displayed by sodium citrate might be related to its ability to complex magnesium or to interfere with the crystal structure during struvite formation. From these experiments it would appear that citrate may be a factor in the natural resistance of whole urine to struvite crystallization.