Activity of some antiseptics against urinary tract pathogens growing as biofilms on silicone surfaces.

The activity of chlorhexidine, mandelic acid and a mandelic/lactic mixture were tested against biofilms of four species of gram-negative nosocomial organisms that commonly infect the catheterized urinary tract. Cells growing on silicone discs were exposed to concentrations of agents used in bladder instillation. Citrobacter diversus biofilms proved to be sensitive to all three agents. Pseudomonas aeruginosa, Proteus mirabilis and Klebsiella pneumoniae all survived well in chlorhexidine but their viability was significantly reduced by the mandelic acid formulations. These results suggest that bladder instillations of mandelic acid or mandelic/lactic acids would be more effective than chlorhexidine in eliminating biofilms from catheter surfaces.