November 3, 2006

Staph Vaccine Shows Promise in Mouse Study

Picture of Staph bacteria magnified 4,780 times Staph bacteria magnified 4,780 times.Janice Carr and Jeff Hageman, Centers for Disease Control and Prevention.

Staph bacteria are a growing public health threat. Many have developed resistance to traditional antibiotics, and a new way to combat them is urgently needed. Scientists have now created a vaccine that significantly protects mice from diverse strains of the bacterium that cause disease in humans. This proof of principle is an important step on the way to creating an effective vaccine for humans.

Staph, which is short for Staphylococcus aureus, is the most common cause of hospital-acquired infection. It’s the leading cause of bloodstream, lower respiratory tract and skin infections. These infections can result in a variety of dangerous illnesses, including endocarditis (inflammation of the heart), toxic-shock syndrome and food poisoning.

In the past few decades, staph has developed resistance to traditional antibiotics, thus allowing infections to spread throughout the body unchecked. Healthy people with no apparent risk factors have been infected by novel and extremely virulent strains recently that they acquired from sources other than hospitals.

Dr. Olaf Schneewind of the University of Chicago led a research group trying, with funding from NIH’s National Institute of Allergy and Infectious Diseases (NIAID), to develop an effective way to prevent staph infections. Their strategy was to create a vaccine that could protect against diverse strains of the bacterium. By searching through staph genome sequences, they identified sequences for 19 surface proteins that were “conserved” across staph strains — that is, they didn’t change much from strain to strain. They then tested these proteins in mice to see if they triggered their immune systems.

The researchers published their results online this week in the Proceedings of the National Academy of Sciences. They identified four proteins — IsdA, IsdB, SdrD and SdrE — that provoked the strongest immune system reactions. They then combined them into a vaccine and tested the combination vaccine in mice. The resulting vaccine protected the mice from all the strains of the bacterium the researchers tested against them, significantly improving their survival. Using the individual proteins as vaccines, in contrast, provided little to no protection.

Dr. Anthony S. Fauci, the director of NIAID, commented, “This finding represents a promising step toward identifying potential components to combine into a vaccine designed for people at high risk of invasive S. aureus infection.”

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