Effect of uropathogens on in vitro encrustation of polyurethane double J ureteral stents

Polyurethane stents are used when there is an obstruction to the flow of urine. A majority of the patients with such stents are at the risk of urinary tract infection and salt encrustation. The present study is aimed at analyzing the in vitro encrustation of calcium oxalate and other salts in the presence of common uropathogens (E. coli and P. mirabilis) on films made from Tecoflex(A (R)), a commercial grade polyurethane. In the absence of uropathogens, sodium ions and ammonia favor calcium adsorption whereas magnesium ions greatly depress it, resulting in increased hydrophillicity of the stent. With E. coli, Mg ions enhance the encrustation of calcium, whereas the other salts decrease its deposition. In case of P. mirabilis, irrespective of the type of salt, it enhances calcium encrustation except in the presence of sodium ions. Adhesion of uropathogens to the stent surface was higher in the presence of bovine serum albumin. Understanding the dynamics between various salts and microorganism in the urine, and urine-stent interface would aid in designing stents that are inert, resist encrustation and biofilm formation.