Allium ‐Derived Compounds Against Multidrug‐Resistant Bacteria: Antibacterial Activity and Synergistic Effects

BACKGROUND AND OBJECTIVES: Antibiotic resistance is a major global health challenge, driven by misuse in medicine and agriculture and the scarcity of new drugs. Allium-derived organosulfur molecules have shown antimicrobial and synergistic effects with antibiotics. This study aimed to evaluate the in vitro antibacterial activity of four Allium-derived compounds and their potential synergy with clinical antibiotics against multidrug-resistant bacteria. METHODS: A total of 330 multidrug-resistant clinical isolates were analyzed, including Gram-positive cocci and Gram-negative bacilli. Antibacterial activity of propyl-propane-thiosulfinate, propyl-propane-thiosulfonate (PTSO), butyl-butane-thiosulfinate, and butyl-butane-thiosulfonate was determined by broth microdilution. Synergy with conventional antibiotics was assessed in 24 representative isolates using the checkerboard method, with interactions classified by the fractional inhibitory concentration index. RESULTS: up to 8 µg/mL against S. aureus, E. faecalis, and S. agalactiae. Activity against Gram-negative bacteria was limited, though PTSO was the most active. Checkerboard assays showed predominantly indifferent interactions, but partial synergy with aminoglycosides was observed in both Gram-positive and Gram-negative bacteria. CONCLUSION: PTSO demonstrated the most significant activity against multidrug-resistant Gram-positive bacteria, with limited impact on Gram-negative strains, and partial synergy with aminoglycosides suggests a potential role for combination therapy.