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How Superbug Staph Aureus Resists Our Natural Defenses

Date:
March 28, 2008
Source:
University of Washington
Summary:
Researchers have uncovered how the bacterium Staphylococcus aureus, including the notorious MRSA (methicillin-resistant Staph aureus) "superbug" strains, resists our body's natural defenses against infection. The work, in Science, could lead to new ways to fight the bacteria.

This scanning electron micrograph depicts numerous clumps of methicillin-resistant Staphylococcus aureus bacteria, commonly referred to by the acronym, MRSA; Magnified 2381x.
Credit: Janice Haney Carr, CDC

Researchers at the University of Washington have uncovered how the bacterium Staphylococcus aureus, including the notorious MRSA (methicillin-resistant Staph aureus) "superbug" strains, resists our body's natural defenses against infection. The work, which was featured on the cover of the March 21 issue of Science, could lead to new ways to fight the bacteria.

Dr. Ferric Fang, UW professor of laboratory medicine and microbiology, and his UW colleagues Dr. Anthony Richardson and Dr. Stephen Libby set out to determine what makes Staph aureus a better pathogen than other bacteria. They focused on a chemical compound called nitric oxide (NO), a natural antibiotic that our cells excrete to protect us from pathogens. For most bacteria, NO creates an environment that keeps invading microbes from undergoing respiration or fermentation, vital chemical processes that allow bacteria to grow.

The researchers found that Staph aureus has a mechanism that allows it to produce lactic acid in the presence of NO, which allows it to maintain its chemical balance and keep growing and thriving in the harsh host environment. When Staph aureus is exposed to NO, it produces the novel enzyme responsible for lactic acid production, along with another enzyme that converts NO to non-toxic products. NO is commonly found in the nose and nasal passages, and is meant to protect people against disease-causing microbes. But Staph aureus is commonly found in the nose despite the presence of NO, the researchers explained.

When the researchers modified Staph aureus to take away its ability to make lactic acid, the bacteria could no longer tolerate NO. The modified bacteria also lost their ability to survive in host immune cells and cause lethal disease in mice.

"MRSA has become an enormous public health problem, by causing both hospital- and community-acquired infections," explained Fang. "Staph aureus has already colonized about one-third of the world's population, so traditional antibiotics will probably not be the complete answer to the MRSA problem."

However, the researchers added, trying to make Staph aureus more susceptible to our natural defenses might lead to new strategies to de-colonize the population and prevent staphylococcal infections.


Story Source:

The above story is based on materials provided by University of Washington. Note: Materials may be edited for content and length.


Cite This Page:

University of Washington. "How Superbug Staph Aureus Resists Our Natural Defenses." ScienceDaily. ScienceDaily, 28 March 2008. <www.sciencedaily.com/releases/2008/03/080324113258.htm>.
University of Washington. (2008, March 28). How Superbug Staph Aureus Resists Our Natural Defenses. ScienceDaily. Retrieved July 22, 2014 from www.sciencedaily.com/releases/2008/03/080324113258.htm
University of Washington. "How Superbug Staph Aureus Resists Our Natural Defenses." ScienceDaily. www.sciencedaily.com/releases/2008/03/080324113258.htm (accessed July 22, 2014).

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