How 'superbug' Staph aureus evades body's natural defences

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Washington, March 25 : Washington University researchers claim to have discovered how the bacterium Staphylococcus aureus evades the body's natural defences against infection.

This work attains significance as it may pave the way for potential strategies to fight the bacteria, including the notorious MRSA (methicillin-resistant Staph aureus) "superbug" strains.

The researchers say that they undertook a study to determine what makes Staph aureus a better pathogen than other bacteria.

The group says that the study was focussed on a chemical compound called nitric oxide (NO), which is known to be a natural antibiotic that the cells excrete to prevent the body against pathogens.

The researchers say that their study revealed a mechanism that allows Staph aureus to produce lactic acid in the presence of NO, which enables it to maintain its chemical balance and keep growing and thriving in the harsh host environment.

According to them, an exposure to NO causes Staph aureus to produce an enzyme responsible for lactic acid production, along with another enzyme that converts NO to non-toxic products.

Generally, NO is found in the nose and nasal passages, and protects people against disease-causing microbes. However, despite its presence, Staph aureus is also commonly found in the nose.

When, during the study, the research team modified Staph aureus to take away its ability to make lactic acid, the bacteria could no longer tolerate NO.

They observed that the modification had also caused the bacterial to lose their ability to survive in host immune cells as well as the ability to cause lethal disease in mice.

"MRSA has become an enormous public health problem, by causing both hospital- and community-acquired infections. 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," said Dr. Ferric Fang, a professor of Laboratory Medicine and Microbiology at the university.

He believes that trying to make Staph aureus more susceptible to our natural defences may lead to new strategies to de-colonize the population and prevent staphylococcal infections.

ANI

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