Inhibitory effects of aqueous garlic extract, garlic oil and four diallyl sulphides against four enteric pathogens

Abstract

The inhibitory effects of aqueous garlic extract, garlic oil and four diallyl sulphides naturally occurring in this oil against Escherichia coli, Enterobacter cloacae, Enterococcus faecalis, and Citrobacter freundii (total 291 clinical isolates) were studied. The MIC values of four diallyl sulphides against the four enteric pathogens followed the order diallyl monosulphide > diallyl disulphide > diallyl trisulphide > diallyl tetrasulphide (p<0.05). Most interactions of four antibiotics (meropenem, ceftazidime, imipenem and gentamicin) with diallyl polysulphide, determined as FIC index, showed synergistic or additive effects. Garlic oil at 2X MIC reduced original inoculum to ≤ 3 log 10/mL within 8 hr; and 4X MIC reduced original inoculum to < 2log 10/mL in all test enteric pathogens within 6 hr. The intake of aqueous garlic extract in humans provided the antibacterial activity in plasma, determined by inhibitory zone. These results suggested that aqueous garlic extract, garlic oil, and diallyl polysulphide may have potential for the prevention or control of infections caused by enteric pathogens.