Unleashing Potent Antimicrobial Synergy: Carnosic Acid and Caffeic Acid Tackle Multidrug-Resistant Mrsa

Abstract

Synergistic antibacterial effect is a promising way to overcome the challenge of drug-resistant microbial contamination in food. In this study, carnosic acid / caffeic acid (CR/CF) combination showed a stronger synergistic antibacterial effect on broad-spectrum multidrug-resistant MRSA than methicillin-sensitive Staphylococcus aureus ATCC2913. The co-treatment also reduced the biofilm formation by 60.7~80% and the structure of MRSA 009 was destroyed and loosed. Metabolic activity of biofilm cells was inhibited by 37.9~68.9%. The exopolysaccharides and extracellular proteins were inhibited by 73.3% and 42.7%, respectively. Furthermore, 1MIC+1/2MIC CR/CF combinations reduced about 2.4 log CFU/cm2 of MRSA on lettuce within 15 min, which had a similar effect as 0.2% NaClO. Thus, CR/CF combination has synergistic antimicrobial efficacy and can be used as an alternative natural food sanitizer of fresh produce.

Keywords: Carnosic acid, Caffeic acid, MRSA, Synergistic antibacterial effect, Biofilm, food matrix