Antibacterial activity of fresh pomegranate juice against clinical strains of Staphylococcus epidermidis

Background: Polyphenols have received a great deal of attention due to their biological functions. Pomegranate (Punica granatum L.) is a polyphenol-rich fruit. In the past decade, studies testing the antimicrobial activity of pomegranates almost exclusively used solvent extracts instead of fresh pomegranate juice (FPJ). The use of FPJ instead of solvent extracts would reduce toxicity issues while increasing patient acceptance. We established a model to test FPJ as a natural antimicrobial agent. Objective: To evaluate the antimicrobial activity of FPJ on clinical isolates of multidrug-resistant Staphylococcus epidermidis strains. Design: Sixty strains of S. epidermidis isolated from ocular infections were grown in the presence of FPJ, and minimum inhibitory concentration (MIC) was determined by broth and agar dilution methods. Results: FPJ at 20% had a MIC equal to 100% (MIC_100%) on all 60 strains tested. This inhibition of FPJ was confirmed by the growth kinetics of a multidrug-resistant strain exposed to different concentrations of FPJ. Additionally, the antimicrobial activity of FPJ was compared against commercial beverages containing pomegranate: Ocean Spray® had a MIC_100% at 20%, followed by Del Valle® with a MIC_15% at 20% concentration only. The beverages Jumex® and Sonrisa® did not have any antimicrobial activity. FPJ had the highest polyphenol content and antioxidant capacity. Conclusions: Overall, FPJ had antimicrobial activity, which might be attributed to its high polyphenol content and antioxidant capacity.