Magazine article Science News

Superbug: What Makes One Bacterium So Deadly

Magazine article Science News

Superbug: What Makes One Bacterium So Deadly

Article excerpt

Some of the most aggressive antibiotic-resistant staph infections gain their advantage with a molecule that punctures the immune cells trying to fight off the bacteria, scientists have discovered. Understanding the role of this molecule in methicillin-resistant Staphylococcus aureus (MRSA) could lead to new therapies for the notoriously hard-to-treat, and sometimes fatal, skin infection.

Staph bacteria are ubiquitous but aren't dangerous unless they seep into an open wound. Even then, antibiotics will usually stop the infection. But some strains of staph that infect hospital patients with weakened immune systems have become resistant to all standard antibiotics, including methicillin.

Now, a newer strain of the flesh-eating disease has swept through schools, day care centers, health club locker rooms, and prisons. So-called community-associated MRSA (CA-MRSA) typically afflicts healthy people because it's especially effective at causing infections in the first place. For now, it's resistant only to methicillin, but scientists fear that it will become resistant to other antibiotics.

In the Oct. 17 Journal of the American Medical Association, Monina Klevens of the Centers for Disease Control and Prevention in Atlanta and her colleagues gave the first statistics on just how widespread MRSA has become. The researchers estimated that 94,360 cases occurred in 2005, leading to 18,650 deaths. They argued that these numbers are on the rise, particularly outside the hospital setting.

In a separate study, Michael Otto of the National Institute of Allergy and Infectious Diseases and his colleagues found a molecule involved in CA-MRSA's success.

While studying small molecules that help a different bacterium, Staphylococcus epidermidis, fight its host, the scientists decided to check whether MRSA carried a similar molecule. They found that CA-MRSA had much more of a protein called phenol-soluble modulin (PSM) than the less virulent MRSA strains associated with hospitals had. …

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