In vitro activity of an aqueous allicin extract and a novel allicin topical gel formulation against Lancefield group B streptococci

Background: Studies have shown the efficacy of intra-partum antibiotics in preventing early-onset
group B streptococcal sepsis. This approach results in a high intra-partum antibiotic use. Worryingly,
the same antibiotics used in prophylaxis are also first-line treatment for neonatal sepsis, and antibiotic
exposure in the peri-natal period has been shown to be a risk factor for late-onset serious bacterial
infections and allergic disease. Antibiotic exposure in the peri-natal period is becoming a major public
health issue; alternative strategies are needed. Garlic has been traditionally used to treat vaginal infections.
Allicin is the main antibacterial agent isolated from garlic.
Objectives: The aim of the study was to investigate the in vitro activity of a novel allicin extract in
aqueous and gel formulation against 76 clinical isolates of Lancefield group B streptococci (GBS).
Methods: MICs and MBCs of allicin were determined for 76 GBS isolates by agar dilution and microtitre
plate methods. Killing kinetics were determined for a selected 16 of the 76 strains. Agar diffusion tests
were compared for allicin liquid and gel (500 mg/L).
Results and conclusions: MICs and MBCs of allicin liquid were 35 to 95 mg/L and 75 to 315 mg/L,
respectively. Time/dose kill curves produced a 2–3 log reduction in cfu/mL within 3 h and no detectable
growth at 8 and 24 h. A novel 500 mg/L allicin gel produced an average zone size of 23+-6 mm
compared with 21+-6 mm for allicin in water. Aqueous allicin is bactericidal against GBS isolates and
maintains activity in a novel gel formulation.

Citation:
Cutler, R.R. et al. (2009) ‘In vitro activity of an aqueous allicin extract and a novel allicin topical gel formulation against Lancefield group B streptococci’ Journal of Antimicrobial Chemotherapy 63 (1) pp.151-154.