Antibacterial activities of isothiocyanates extracted from horseradish (Armoracia rusticana) root against Antibiotic-resistant bacteria

The antibacterial activities of isothiocyanates (ITCs) extracted from horseradish root was determined against 4 strains of antibiotic-resistant bacteria, methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant S. aureus (VRSA), multidrug-resistant Acinetobacter baumanii (MRAB), and multidrug-resistant Pseudomonas aeruginosa (MRPA), and 3 strains of normal pathogenic bacteria, S. aureus, A. baumanii, and P. aeruginosa. The minimum bactericidal concentrations (MBC) of ITCs against MRSA, VRSA, MRAB, and MRPA were 666.7, 666.7, 333.3, and 208.3 μg/mL, respectively, and against S. aureus, A. baumanii, and P. aeruginosa were 833.3, 41.7, and 52.1 μg/mL, respectively. ITCs extracted from horseradish root showed the strongest antibacterial activity against A. baumanii with a MBC of 41.7 μg/mL. Among antibiotic-resistant bacteria, ITCs showed the strongest antibacterial activity against MRPA with a MBC of 208.3 μg/mL. MBC values of vancomycin against MRSA, VRSA, and S. aureus were 1,667.7, 2,000.0, and 1,333.3 μg/mL, levofloxacin against MRAB and A. baumanii were 833.3 and 1,333.3 μg/mL, respectively, norfloxacin against MRPA and P. aeruginosa were 666.7 and 7.8 μg/mL, respectively. ITCs showed stronger antibacterial activities than antibiotics against tested bacteria except P. aeruginosa. These results indicate that ITCs extracted from horseradish root should be candidates for antibacterial agent against antibiotic-resistant bacteria.