Antibiotic Sensitivity of Campylobacter jejuni and Effect of Allicin on Succinate Dehydrogenase Activity
Archeological evidence shows that garlic (Allium sativum) is an antibiotic in use for at least 7000 years. Garlic, originally Asian, has spread worldwide with medicinal properties passed on through generations. Garlic has been analyzed, active ingredients isolated, and two “front-runners”—allicin (the more potent) and S-allylcysteine (the more stable) appear to be the ‘most’ active. The objectives were to demonstrate bactericidal effects of allicin and S-allylcysteine on Campylobacter jejuni (CJ), allicin’s mode of action (MOA), and compare findings to common antibiotics. ^ Seven CJ strains were challenged by allicin and S-allylcysteine with two sets of three trials using microdilution and disc diffusion. Trials show allicin is six times more potent than S-allylcysteine, but when equally mixed, S-allylcysteine did not significantly improve allicin’s potency. Allicin was compared to ten antibiotics and found as effective at higher concentrations. To demonstrate one MOA of allicin, we chose succinate dehydrogenase (SD) as a marker because it participates in the citric acid cycle and the electron transport chain, making it metabolically vital. Allicin’s MOA with SD has been previously demonstrated in E-Coli and Salmonella, but NOT in Campylobacter jejuni. In demonstrating Allicin’s bactericidal effect on CJ, our experiments show an average Minimum Inhibitory Concentration of 7.6 µg/mL. ^ Our MOA hypothesis is as follows: “Allicin lethally alters the rate at which the Complex II enzyme (Succinate Dehydrogenase) catalyzes the conversion of succinate to fumarate in the Citric Acid Cycle.” Several trials of microwell assays were performed simulating the chemical environment of Complex II enzymatic action with various concentrations of Allicin added. Controls were included to generate valid comparisons. Results were quantified using kinetic spectrophotometric analysis over two-hour periods in thirty-second intervals. Allicin is significant because despite multi-drug resistance by CJ strains to other drugs, they are susceptible to allicin, which is effective against gram positive and gram negative bacteria. For medical applications, a stable, redesigned allicin molecule must be developed which does not cause vascular endothelial cell damage as allicin does now. ^
Richard Arnold Yorke,
"Antibiotic Sensitivity of Campylobacter jejuni and Effect of Allicin on Succinate Dehydrogenase Activity"
ETD Collection for Tennessee State University.