Researchers have gained a greater understanding of the biology of staphylococcus skin infections in mice and how the mouse immune system mobilizes to fight them. A study appears in the Proceedings of the National Academy of Sciences of the United States of America. Community acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) typically causes skin infections but can spread throughout the body to cause invasive infections such as sepsis, and possibly death.
These CA-MRSA bacteria are becoming increasingly resistant to multiple antibiotics, making them especially difficult to treat. In healthy people, the body’s natural immune defenses typically keep CA-MRSA infections in the skin, and appropriate antibiotics can effectively treat them. However, patients who are immunocompromised have difficulty fighting the bacteria, which can become invasive and cause life-threating infections.
Lloyd Miller, M.D., Ph.D., an associate professor of dermatology at the Johns Hopkins University School of Medicine, notes that CA-MRSA and other multidrug resistant bacteria are becoming a bigger problem in healthcare, as most antibiotics no longer work against these infections and few new antibiotics are being developed in the pipeline. In the case of CA-MRSA, sometimes only two or three oral antibiotics remain that can treat these infections.
Miller and his team are working to understand the specific details of the mouse immune system’s MRSA-fighting program to develop a way to probe the human immune system to develop alternative immune-based treatments that could work along with antibiotic regimens or eliminate the need for antibiotics altogether.
In their previous research, Miller and his team discovered that a cytokine protein called IL-17 is critical for turning on the host defense against staph infections. However, until know, they did not know which cell produced it, particularly which type of T cell. Also, there are two types of IL-17, one called IL-17A and the other IL-17F, but the researchers didn’t know if one or the other or both are required to mount the host response against CA-MRSA. So, they teamed up with colleagues at the National Institutes of Health (NIH) who had engineered mice that would glow different colors depending on which form of IL-17 the mouse was making. The researchers then injected MRSA in the skin of these mice and found that the infected skin glowed green and red. They concluded this to mean that both types of IL-17 are involved in the immune response to the bacteria.