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 (R² = 0.9988), and the accuracy of the model was verified (R² = 0.9527). Values of CAR, TM, and the quadratic term CAR² 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 log₁₀ reduction) determined by ridge analysis were 8.3% CB +0.04% CAR +0.04% TM at 37 °C for 1 min. 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.

Keywords:

• Antimicrobial mixtures
• biofilm eradication; Escherichia coli
• natural products
• optimization modeling
• uropathogenic

Acknowledgements

This study was supported by the Korea Research Foundation (NRF-2016R1A2B2012743). The authors thank the School of Life Sciences and Biotechnology of Korea University for BK 21 PLUS, and the Institute of Biomedical Science and Food Safety, Korea University Food Safety Hall, for enabling access to their equipment and facilities. The authors are also grateful to Dr A.C. Matin of Stanford University School of Medicine for generously providing the clinical UPEC isolate used in this study.

Disclosure statement

No potential conflict of interest was reported by the authors.