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April 2002
Vol. 5, No. 4, p 12.
news in brief

Garlic: A natural antibiotic

opening artAs powerful antibiotics lose their punch against “superbugs” such as vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA), scientists are searching for new antimicrobial agents from natural sources. Allicin, the major component of garlic, is one such agent, and it was recently shown to be potent against VRE and MRSA in two studies presented at the 41st Interscience Conference on Antimicrobial Agents and Chemotherapy in Chicago in December.

A study conducted by Jaya Prakash and colleagues at the National University of Health Sciences in Lombard, IL, found that allicin has potent activity against VRE in vitro. “The basic problem with VRE is that it colonizes the gut,” says Prakash. “Many antibiotics used to control or prevent colonization also affect the normal flora.” The ideal solution, she explains, would be to prevent colonization with a food substance, given the safety of such compounds over antibiotics. Furthermore, she adds, the chance of organisms developing resistance is low. “Even with small amounts of these agents, they don’t become resistant.”

In their studies, the scientists obtained allicin from garlic tablets and determined its concentration. In vitro testing showed that microgram quantities were sufficient to significantly inhibit the growth of VRE. In contrast, 4000 µg of allicin corresponds to the amount found in one clove of garlic. Up to 25 g of garlic a day can be consumed without posing a risk of toxic side effects.

Prakash cautions that it is too early to say how much allicin intake will reap intestinal rewards against VRE. “In vitro [activity] does not correlate to in vivo activity,” she cautions. And the bad news is that allicin is destroyed when garlic is cooked in oil.

In the next stage of their work, they will study the effects of allicin on the gut microflora of animals to determine the concentration of allicin required to be efficacious in vivo.

In another study, Ron Cutler, from the University of East London (U.K.) and colleagues found that allicin liquid and cream formulations were highly potent against clinical isolates of MRSA, including those resistant to mupirocin—the agent commonly used to eradicate MRSA carriage among hospital staff and patients. Topical allicin formulations could be used as a safe, natural alternative to mupirocin for eliminating the carriage of MRSA and other microbes from the nose, skin, wounds, and dressings, he reports, and they could also be used in soaps and antibacterial agents.

NICOLE JOHNSTON

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