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article imageTackling flesh-eating bacteria

By Tim Sandle     Jan 20, 2014 in Science
Scientists are trying to understand how a relatively harmless microorganism can sometimes transform into the agent of "flesh-eating disease." Some new research throws up some possible answers.
Streptococcus pyogenes, or Group A streptococcus (GAS) is mostly harmless and is carried by many people. However, sometimes it can "go wild" and cause life-threatening diseases such as necrotizing fasciitis (commonly known as "flesh-eating disease") and streptococcal toxic shock syndrome.
Despite some media headlines, necrotizing fasciitis is a rare infection. It is, nonetheless, quite nasty. The infection begins locally at a site of trauma, which may be severe (such as the result of surgery), minor, or even non-apparent. Patients usually complain of intense pain that may seem excessive given the external appearance of the skin. Patients initially present with signs of inflammation, fever and tachycardia. With progression of the disease, often within hours, tissue becomes progressively swollen, the skin becomes discolored and develops blisters. There may be discharge of fluid, said to resemble "dish-water." Diarrhea and vomiting are also common symptoms.
A science team has identified a novel mechanism that influences GAS virulence at the early steps of the infection. They found that when GAS adheres and infects the host's cells, it delivers into these cells two streptolysin toxins. These toxins impair the body's mechanism for quality control of protein synthesis. This in turn triggers a defensive stress response which, among other things, also increases the production of the amino acid asparagine. GAS senses the increased asparagine level and alters its gene expression profile -- and its rate of proliferation, which can be deadly in the host.
The research team further discovered that asparaginase, a protein that digests asparagine and is a widely-used chemotherapeutic agent against leukemia, arrests GAS growth in human blood and in a mouse model of human bacterial infection. Asparginase has never before been used to treat GAS infections.
The research was undertaken at Hebrew University of Jerusalem's Faculty of Medicine. The findings have been published in the journal Cell, in a paper titled “An Extracellular Bacterial Pathogen Modulates Host Metabolism to Regulate Its Own Sensing and Proliferation.”
More about Flesh eating, Streptococcus, Bacteria, Infection
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