Tipsheet: Journals of the American Society for Microbiology

January 10, 2001

For garlic, powder more effective against bacteria than oil
Garlic may be good for your health, but it appears that garlic powder works better than garlic oil in fighting bacteria according to researchers from the United Kingdom. They report their results in the January 2001 issue of the journal Applied and Environmental Microbiology.

The antimicrobial effects of garlic have long been known, but little research has been done to date on garlic oil. The purpose of this study was to compare the abilities of garlic oil and garlic powder on a variety of bacteria known to cause gastrointestinal illness. For nearly every species tested, garlic powder had a greater killing effect than garlic oil. "Garlic powder was more active than garlic oil against most bacteria, although some properties of garlic oil are identified as offering greater therapeutic potential," say the researchers. "Further exploration of the potential of garlic powder and garlic oil in enteric disease control appears warranted."

(Z.M. Ross, E.A O'Gara, D.J. Hill, H.V. Sleightholme and D.J. Maslin. 2001. Antimicrobial properties of garlic oil against human enteric bacteria: Evaluation of methodologies and comparisons with garlic oil sulfides and garlic powder. Applied and Environmental Microbiology, 67: 475-480.)

Engineered HIV requires antibiotic to replicate
Researchers at the University of Amsterdam have genetically engineered a live-attenuated human immunodeficiency virus (HIV) that will only reproduce in the presence of the antibiotic doxycycline. Their research, which may help in the development of a safe, live HIV vaccine appears in the January issue of the Journal of Virology.

The designer virus (HIV-rtTA) was created in response to concerns about current live HIV vaccines. The genetic instability of current candidate vaccine viruses suggests the possibility that they could convert to once again cause disease.

To improve the safety of HIV candidate vaccines, the researchers replaced specific genetic sequences the virus uses for replication with genes from E. coli bacteria, widely used to regulate gene expression in other applications. The result is an attenuated HIV that requires the antibiotic doxycycline in order to replicate, and the concentration of the antibiotic regulates the rate of replication. "It is anticipated that HIV-rtTA vaccine viruses will be able to induce a protective immune response by doxycycline-induced replication, after which replication can be turned off by the withdrawal of doxycycline," say the researchers. "In case a booster vaccination is required to mount an optimal immune response, replication can be switched on transiently at later times by [administering] doxycycline."

(K. Verhoef, G. Marzio, W. Hillen, H. Bujard and B. Berkhout. 2001. Strict control of human immunodeficiency virus type 1 replication by a genetic switch: Tet for tat. Journal of Virology, 75: 979-987.)

No resistant enterococci found for one antibiotic
In a study of 300 strains of enterococcal bacteria at the University of Manitoba in Canada only one antibiotic, nitrofurnatoin, was effective against them all. The results of the study appear in the January 2001 issue of the journal Antimicrobial Agents and Chemotherapy.

Enterococci are a common cause of urinary tract infections, but can cause a variety of other diseases including endocarditis (an infection of the heart) and meningitis. Doctors and hospitals have become increasingly concerned about these bacteria in recent years as they have developed resistance to most antibiotics, including the drug of last resort, vancomycin.

In the study, the researchers tested the effectiveness of eight different antibiotics on 300 enterococcal isolates from the hospital, a third of which were resistant to vancomycin. Only the antibiotic nitrofurantoin was effective against them all.

"We conclude that nitrofurantoin may provide effective treatment of urinary tract infections caused by vancomycin-resistant enterococci," say the researchers. Nitrofurantoin is currently available in the United States under several brand names and generically.

(G.G. Zhanel, D.J. Hoban and J.A. Karlowsky. 2001. Nitrofurantoin is active against vancomycin-resistant enterococci. Antimicrobial Agents and Chemotherapy, 45: 324-326.)

American Society for Microbiology

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