D-063. The Effect Allicin on Bacterial Biofilm Formation and Quorum Sensing

C. Toth, D. Downes;
Palm Beach Atlantic Univ., West Palm Beach, FL.

Background Many bacterial species establish biofilms by attaching onto extra-cellular surfaces. Allium sativum has been identified as having antimicrobial properties (Ellmore and Feldberg 1994) and thus of interest for its potential ability to interfere with biofilm formation. The purpose of this work was to identify the active ingredients of garlic through high performance liquid chromatography and test each of the constituents for antimicrobial activity and biofilm formation using P. aeruginosa and S.aureus. Materials and Methods HPLC analysis was used to separate the components of garlic and identify the active ingredient. A garlic clove was crushed and resuspended in cold deionized water. The solution was filtered using a 0.45um nylon filter and loaded into the HPLC with a mobile phase of 50:50 mix of methanol and water at a flow rate of 1.0 ml/min using an Altec ODS-S5U column.The active single peaks of interest (5.5, 10, 13.5 min) were separated utilizing the HPLC fraction collector. All isolated componenents were tested for antimicrobial activity and the effect on the ability of bacteria to form biofilm. The organisms were placed in well trays and treated individually with the isolated garlic compounds. The final well was treated with a sample of crushed garlic filtered through 0.45 um nylon filter. A control well was prepared without the addition of allicin.To assay for biofilm formation, the stationary phase microorganisms were diluted 1:100 in fresh LB broth supplemented with 0.2wt % glucose medium and grown in 96-well microtiter plates for 24hours at 30oC. Biofilm formation was estimated by crystal violet staining of the adherent organisms. Results and Conclusion HPLC showed three peaks with the single peak at 10 min proportionally larger that the other two. Of the components fractionated, the active ingredient was identified as allicin, and was shown to have antimicrobial activity. Our results show that allicin is responsible for interference in biofilm construction and is likely a disruption in the bacteria’s quorum sensing. The difference in how allicin affects gram-positive and gram-negative bacteria sheds light on the differences in biofilm formation between the two types of bacteria.