Response surface modeling of reductions in uropathogenic Escherichia coli biofilms on silicone by cranberry extract, caprylic acid, and thymol

Abstract

A response surface methodology was used to build a model to predict reductions in uropathogenic Escherichia coli biofilms in response to three compounds: cranberry extract [CB] at 3.0-9.0%, and caprylic acid [CAR] and thymol [TM] at 0.01%-0.05%. The predictive model for microbial reduction had a high regression coefficient (R-2=0.9988), and the accuracy of the model was verified (R-2=0.9527). Values of CAR, TM, and the quadratic term CAR(2) were the most significant (P<0.0001) for bacterial reduction. Interactions between CB and CAR, and TM and CB, also affected bacterial reduction. The optimum conditions (a 5.8 log(10) reduction) determined by ridge analysis were 8.3% CB +0.04% CAR +0.04% TM at 37 degrees C for 1min. The model could be used to predict the most cost-efficient amounts of antimicrobial agents for anti-urinary tract infection products such as catheter lock solution and antimicrobial coatings for catheters.