ABSTRACTThein vitroantibacterial effects of diallyl sulfide (DAS) against the Gram-negative periodontopathogenAggregatibacter actinomycetemcomitans, the key etiologic agent of the severe form of localized aggressive periodontitis and other nonoral infections, were studied.A. actinomycetemcomitanswas treated with garlic extract, allicin, or DAS, and the anti-A. actinomycetemcomitanseffects of the treatment were evaluated. Garlic extract, allicin, and DAS significantly inhibited the growth ofA. actinomycetemcomitans(greater than 3 log;P< 0.01) compared to control cells. Heat inactivation of the garlic extracts significantly reduced the protein concentration; however, the antimicrobial effect was retained. Purified proteins from garlic extract did not exhibit antimicrobial activity. Allicin lost all its antimicrobial effect when it was subjected to heat treatment, whereas DAS demonstrated an antimicrobial effect similar to that of the garlic extract, suggesting that the antimicrobial activity of garlic extract is mainly due to DAS. AnA. actinomycetemcomitansbiofilm-killing assay performed with DAS showed a significant reduction in biofilm cell numbers, as evidenced by both confocal microscopy and culture. Scanning electron microscopy (SEM) analysis of DAS-treatedA. actinomycetemcomitansbiofilms showed alterations of colony architecture indicating severe stress. Flow cytometry analysis of OBA9 cells did not demonstrate apoptosis or cell cycle arrest at therapeutic concentrations of DAS (0.01 and 0.1 μg/ml). DAS-treatedA. actinomycetemcomitanscells demonstrated complete inhibition of glutathione (GSH)S-transferase (GST) activity. However, OBA9 cells, when exposed to DAS at similar concentrations, showed no significant differences in GST activity, suggesting that DAS-induced GST inhibition might be involved inA. actinomycetemcomitanscell death. These findings demonstrate that DAS exhibits significant antibacterial activity againstA. actinomycetemcomitansand that this property might be utilized for exploring its therapeutic potential in treatment ofA. actinomycetemcomitans-associated oral and nonoral infections.
EXPERIMENTAL STUDY FOR EVALUATION OF ANTIMICROBIAL ACTIVITY OF THE AQUEOUS GARLIC EXTRACT IN TREATMENT OF ARTHRITIS IN RABBITS
