Tips from the journals of the American Society for Microbiology


Light May Rapidly and Painlessly Kill Bacteria That Cause Gum Disease

Exposure to broadband light may provide a rapid and painless method for killing the bacteria that cause plaque and periodontal disease, say researchers from Texas and Massachusetts. Their findings appear in the April 2005 issue of the journal Antimicrobial Agents and Chemotherapy.

Dental plaque is a film that forms naturally on teeth and consists of many different bacteria. While these bacteria often prove harmless they can also trigger tooth decay resulting in an infection in the gums, or periodontitis. If left untreated this condition can cause bone deterioration and loss of teeth. However, current treatment options often involve painful procedures such as scaling and surgery.

In the study pure samples and those containing dental plaque were collected from patients with chronic periodontitis and exposed to varying degrees of broadband light. This is the same light source commonly used in teeth whitening procedures. The researchers compared bacterial presence before and after light treatment and found that bacteria were significantly reduced after exposure.

"These data suggest that visible light could be used prophylactically to stabilize the normal microbial composition of plaque by suppressing potentially pathogenic BPB," say the researchers. "Compared with other forms of periodontal therapy (scaling, mouthwashes, surgery) this form of treatment would offer many advantages; it is painless, rapid, and devoid of drug toxicity, has no effect on taste, and is selective in its effect."

(N.S. Soukos, S. Som, A.D. Abernethy, K. Ruggiero, J. Dunham, C. Lee, A.G. Doukas, J.M. Goodson. 2005. Phototargeting oral black-pigmented bacteria. Antimicrobial Agents and Chemotherapy, 49. 4: 1391-1396.)

New Approach for Controlling Drug-Resistant Staphylococci

Researchers from Ireland have identified a bacteriophage that may inhibit drug-resistant Staphylococci infections. Their findings appear in the April 2005 issue of the journal Applied and Environmental Microbiology.

Antibiotic resistance to emerging strains of Staphylococci is of major concern among today's medical community. These bacteria are responsible for a wide variety of human infections ranging from minor abscesses to fatal sepsis. Statistics show that over 95 percent of Staphylococcus aureus infections do not respond to preliminary rounds of antibiotics such as penicillin and now researchers are isolating new strains capable of resisting vancomycin, one of the most potent antibiotics available today.

In the study a bacteriophage (phage K) was tested for its ability to inhibit strains of S. aureus found in hospitals and other species of Staphylococcus associated with bovine infections. It was determined that modified phage K was able to weaken all fourteen strains isolated in the sample bacteria. A handwashing study was also conducted in which a solution containing phage K was analyzed for its ability to kill Staphylococci on human skin. Results showed a significant reduction in bacteria in comparison to hands washed with a phage-free solution.

"In this study we demonstrate that the exclusively lytic phage K has particular applications in the prevention and/or treatment of infections caused by antibiotic-resistant staphylococci," say the researchers. "In this respect, we have shown its ability to kill a broad range of newly isolated pathogenic staphylococci, including both human and veterinary strains."

(S. O'Flaherty, R.P. Ross, W. Meaney, G.F. Fitzgerald, M.F. Elbreki, A. Coffey. 2005. Potential of the polyvalent anti-Staphylococcus bacteriophage K for control of antibiotic-resistant staphylococci from hospitals. Applied and Environmental Microbiology, 71. 4: 1836-1842.)

Interleukin-12 May Protect Against Lethal Respiratory Infection

Treatment with interleukin-12 may protect against tularemia in humans, say researchers from Albany Medical College in New York. Their findings appear in the April 2005 issue of the journal Infection and Immunity.

Tularemia, caused by the bacterium Francisella tularensis, is an extremely virulent respiratory disease with a mortality rate as high as thirty-five percent. Transmitted through insect bites, infected carcasses, contaminated drinking water and aerosols, this disease has raised concerns as a potentially dangerous biological weapon.

In the study mice were inoculated with interleukin-12 (IL-12) and challenged twenty-four hours later with a lethal dose of F. tularensis. Researchers determined that treatment with IL-12 prior to infection greatly reduced the amount of bacteria in the lungs, livers and spleens ultimately resulting in survival.

"These results demonstrate the ability of exogenous IL-12 to induce protective immunity against this bacterial threat in the respiratory tract," say the researchers.

(N.S. Duckett, S. Olmos, D.M. Durrant, D.W. Metzger. 2005. Intranasal interleukin-12 treatment for protection against respiratory infection with the Francisella tularensis live vaccine strain. Infection and Immunity, 73. 4: 2306-2311.)

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Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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