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In a new study, researchers from the University of Iowa have uncovered why staphylococcal infective endocarditis, which is a deadly bacterial infection in the heart valves, is so lethal. This type of infection kills nearly 20,000 Americans per year and until now, researchers were unsure what causes its fatal side effects. In this new study, researchers found that the toxins, also called superantigens that are produced from the bacteria, Staphylococcus aureus could be the culprits.

"The function of a superantigen is to 'mess' with the immune system," stated Patrick Schlievert, Ph.D according to a press release. Schlievert is a professor from the University and the chair of microbiology at the University's Carver College of Medicine. "Our study shows that in endocarditis, a superantigen is over-activating the immune system, and the excessive immune response is actually contributing very significantly to the destructive aspects of the disease, including capillary leakage, low blood pressure, shock, fever, destruction of the heart valves, and strokes that may occur in half of patients."

For this study, the researchers decided to block the superantigens from working to see if they could prevent strokes related to endocarditis in animal models. The researchers utilized a specific strain of methicillin resistant staph aureus (MRSA), which is very common in humans. Along with this strain, the researchers also looked into versions of the bacteria that cannot produce superantigens. Based from the comparisons of these strains, the researchers concluded that the presence of superantigens produced by some of the strains of staph bacteria contributed to the deadly side effects of endocarditis and sepsis. The specific culprit was the superantigen staphylococcal enterotoxin C (SEC).

"The idea is that either therapeutics or vaccination might be a strategy to block the harmful effects of the superantigens, which gives us the chance to do something about the most serious complications of staph infections," Schlievert stated.

The researchers discovered that SEC causes lethal side effects because it disrupts the immune system, causes low blood pressure and contributes to toxicity to the cells lining the heart. The researchers hope that this discovery could help with future treatment plans to prevent these dangerous side effects.

The study was published in the journal, mBio.