New methods of preventing MRSA revealed

Two studies have emerged that suggest there may be ways to prevent infections caused by the drug resistant bacteria Staphylococcus aureus, also known as MRSA.

In each case, researchers were able to reduce the virulence of MRSA infections in laboratory mice, suggesting that some combination of the two may protect people from MSRA and even provide a lasting immunity. MSRA infections are the leading cause of death from infectious disease in the United States, according to

Creating a vaccine that protects against drug-resistant staph has been difficult because most vaccines rely on stimulating an immune response in the body that attacks the microbe and prevents its return. MSRA can short circuit its host’s immune response.

Olaf Schneewind, a professor and the chair of microbiology at the University of Chicago and the senior author of both studies, explained to that MSRA can hold off the immune response long enough that it can escape from the blood stream and enter various tissues. Once ensconced in the body, MSRA builds a protective capsule and replicates, allowing it to spread further throughout the body.

"Staph aureus is the world champion of immune suppression," Schneewind said. "Even when the infection can be cleared with antibiotics and surgery, the patient has no immunity. So these infections often recur."

Schneewind and his team were able to isolate two vaccine targets. One, known as protein A, binds with the white blood cells that produce antibodies. MSRA cross-links two receptors on the white blood cell, triggering cell death. Without the white blood cell, there is no immune response.

MSRA bacteria with a mutated form of protein A, created by Schnweewind, were unable to cross-link white cells and an immune response was triggered. This immune response reduced tissue damage by the bacteria and prevented, or delayed, death in mice.

“I believe that protein A may be the key to making a staphylococcal vaccine,” Schnweewind said.

The second targets are a set of clotting proteins from MSRA - coagulase and von Willebrand factor binding protein, or vWbp. They are engaged to build a protected area the bacteria use to replicate in after leaving the blood stream. Bacteria that lacked these two factors were unable to persist in infected tissues.

Schneewind and his colleagues found that by creating antibodies to these factors and transferring them to mice, they could protect the mice from infection. Furthermore, even when injected with the purified form of these clotting factors from different bacteria, E. coli, the mice were able to live longer and showed fewer abscesses.

Scientists are currently testing the ability of a vaccine made by a combination of both approaches.