Tips from the journals of the American Society for Microbiology

July 18, 2005

Visible Light May Kill Bacteria That Infects the Human Stomach

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.)

Mediterranean Fruit Fly May Transmit Human Pathogens to Fruit

The Mediterranean fruit fly has the capability to contaminate commercial and wild fruits with bacteria harmful to humans say researchers from Israel. They report their findings in the July 2005 issue of the journal Applied and Environmental Microbiology.

The Mediterranean fruit fly is considered to be a major menace to the commercial fruit industry worldwide. They feed on animal feces for protein in order to produce eggs, which they then lay in fruit by puncturing the skin and injecting them. Outbreaks of food-borne diseases associated with fresh produce consumption are rapidly increasing, reinforcing the need to identify the source of contamination.

In the study flies were fed feces contaminated with Escherichia coli and caged with intact apples. After limited exposure researchers found the apples to be contaminated with E. coli and rinsing them with tap water did not rid them of the bacteria. The flies studied harbored E. coli in their systems up to seven days after infection.

"These findings highlight the potential of the fly to carry human pathogens and to serve as a vector for transmission of food-borne diseases," say the researchers.

(S. Sela, D. Nestel, R. Pinto, E. Nemny-Lavy, M. Bar-Joseph. 2005. Mediterranean fruit fly as a potential vector of bacterial pathogens. Applied and Environmental Microbiology, 71. 7: 4052-4056.)

New Species of Adenovirus Identified in Falcons

Midwest and west coast researchers have identified a new species of adenovirus in falcons. Their findings appear in the July 2005 issue of the Journal of Clinical Microbiology.

Falcons, birds of prey, are scarcely found today largely due to destruction of their natural habitat in the early 20th century as well as pesticide exposure, poachers and illness. As a result of their dwindling population researchers have minimal knowledge of diseases that naturally occur among these birds. In 1996 an outbreak of disease at a captive breeding facility in Idaho exhibiting anorexia, dehydration, diarrhea and sudden death claimed the lives of 68 falcons between two different species. Extensive testing on all the birds that died resulted in the identification of a new adenovirus species, distantly related to a group of avian viruses known as Aviadenovirus.

Adenoviruses usually exhibit low levels of virulence and have been recognized in at least forty vertebrate species. Infection generally manifests intestinal or respiratory symptoms, with serious illness only developing in conjunction with exposure to other viral or bacterial pathogens. However, emergence of a new viral strain or cross-species transmission can result in higher fatality rates ranging from seventy to ninety percent.

Following the 1996 outbreak, researchers monitored a variety of falcon species co-housed together over a five-year period. The same virus was found in five different species indicating widespread infection among falcons located in western and midwestern North America.

"These findings indicate that this newly recognized adenovirus is widespread in western and midwestern North America and can be a primary pathogen in different falcon species," say the researchers.

(M. Schrenzel, J.L. Oaks, D. Rotstein, G. Maalouf, E. Snook, C. Sandfort, B. Rideout. 2005. Characterization of a new species of adenovirus in falcons. Journal of Clinical Microbiology, 43. 7: 3402-3413.)

American Society for Microbiology

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