Treatment with visible light may kill the bacteria that commonly cause ulcers in humans say researchers from Massachusetts and Minnesota. Their findings appear in the July 2005 issue of the journal Antimicrobial Agents and Chemotherapy.

Helicobacter pylori, often referred to as the world's "commonest infectious agent", colonizes in the stomach causing chronic gastritis, gastric ulcers, and was recently implicated in the development of gastric cancer. Infecting more than fifty percent of the world's population and up to ninety percent of the population in some countries, the bacterium can persist, once acquired, sometimes for life. A twenty percent failure rate in antibiotic therapy reinforces the need for alternative treatment methods.

In the study various strains of H. pylori were cultured and found to produce porphyrins, naturally occurring compounds, which can cause photosensitivity. When the cultures were exposed to visible broadband light, results showed both virulent and drug-resistant strains of H. pylori were killed. Blue/violet light was found to be the most effective and the research indicates that photodynamic therapy, a combination of medication and radiation would be the method of treatment.

"We have shown that all tested strains of H. pylori naturally accumulate a mixture of PPIX and CP (porphyrins) that can sensitize the bacteria to killing by visible light, particularly blue light," say the researchers. "This finding suggests that a novel phototherapy approach may be applied in the human stomach to eliminate H. pylori infection."

(M.R. Hamblin, J. Viveiros, C. Yang, A. Ahmadi, R.A. Ganz, M.J. Tolkoff. 2005. Helicobacter pylori accumulates photoactive porphyrins and is killed by visible light. Antimicrobial Agents and Chemotherapy, 49. 7: 2822-2827.)

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Contact: Carrie Patterson
cpatterson@asmusa.org
202-942-9389
American Society for Microbiology
18-Jul-2005