Synergistic antimicrobial effect of ascorbic acid and nicotinamide with rifampicin and vancomycin against SCCmec type IV Methicillin-Resistant Staphylococcus aureus (MRSA)

Background: MRSA is a pathogenic bacteria involved in a wide spectrum of human diseases. Many virulence factors promote this widespread propagation. One important factor is acquiring antibiotic resistance genes which leads to a reduction in availability and efficacy of therapy options. Recently, research suggests antioxidants remarkable antimicrobial effect against superbugs like MRSA, showing synergistic effect when accompanied by antimicrobial therapy. Henceforth, the article is aimed to examine the synergistic effect of ascorbic acid and nicotinamide with a panel of antibiotics used in antimicrobial therapy of MRSA. Material and Methods: 2 SCC mec type IV MRSA reference strains (EMRSA-15 and USA300) and 10 MRSA clinical isolates were used in this article. SCC mec typing was conducted on the 10 clinical isolates via multiplex PCR after identification. Synergy experiments of antioxidants and antibiotics were evaluated via checkerboard assay. MIC of each agent was conducted in accordance with CLSI M100 guidelines through 2-fold microdilution assay. Results and Discussion: synergy (FIC<0.5) was demonstrated for ascorbic acid (1/2-1/4 MIC) with rifampicin (1/2-1/8 MIC), also, 1/2 to 1/16 MIC of ascorbic acid when associated with vancomycin at 1/2 MIC. Similarly, nicotinamide (1/2-1/16 MIC) showed synergistic response when paired with low concentrations of rifampicin (1/2-1/16 MIC), also, when associating nicotinamide (1/4-1/16 MIC) with vancomycin (1/2 MIC). All reduced MICs due to synergistic combinations demonstrated statistical significance (P<0.05). Conclusion: The synergistic activity demonstrated in associating antioxidants and antibiotics is a promising notion in managing superbugs. However, more research required to better understand the synergy mechanism and for utilization in clinical care.