Abstract

The antimicrobial effects of garlic (Allium sativum) against pathogenic microorganisms have been well documented.  It is generally stated that garlic exhibits differential inhibition between pathogenic and beneficial bacteria. Though there is substantial evidence to support the claim for pathogens, there is limited literature on its effects on beneficial bacteria, specifically probiotic bifidobacteria. This study aimed to investigate the antimicrobial effects of different garlic preparations on five strains of bifidobacteria. The disk diffusion assay revealed antibacterial activity of different garlic preparations characterised by zones of inhibition ranging from 13.0 ± 1.7 to 36.7 ± 1.2 mm. Minimum inhibitory concentration (MIC) values for garlic clove extract ranged from 75.9 to 303.5 mg/ml (estimated 24.84 to 99.37 µg/ml allicin). Bifidobacterium lactis Bi-07 300B was on average the most resistant to garlic, followed by B. lactis Bb12, B. longum LMG 13197, B. longum Bb356 and B. bifidum 11041, being most sensitive. This study reveals for the first time, susceptibility of bifidobacteria to antibacterial activity of garlic. Caution is therefore advised when using probiotic bifidobacteria and garlic simultaneously.

Key words: Allicin, Allium sativum, Bifidobacterium, garlic, probiotic