Between one and three million people a year in the United States are diagnosed
with sepsis, and between 15 and 30% of them die. Severe
bacterial sepsis is characterized by an extreme immune response,
inflammation, reduced blood flow, clotting, and organ failure.
Staphylococcus epidermidis bacteria - typically skin dwellers - can infect the bloodstream and cause a life-threatening condition known as sepsis. It is a significant health concern for hospitalized infants, children and anyone with implanted medical devices.
Methicillin-resistant strains of S. epidermidis (MRSE) cause most sepsis cases. Notably, methicillin resistance rates in S. epidermidis exceed those in the more-familiar S. aureus (MRSA), and methicillin resistance makes MRSE infections difficult to treat.
Now, National Institutes of Health (NIH) scientists have identified an S. epidermidis toxin (PSM-mec) that is released into the bloodstream and contributes to sepsis. The investigators say this is the first time a toxin from S. epidermidis or closely related bacteria has been linked to sepsis.
In tissue studies using S. epidermidis strains, the group found that the PSM-mec toxin helped the bacteria survive in human blood and resist attack by neutrophils, important immune system fighters. In a mouse model, the toxin significantly increased disease and stimulated the immune response, which worsened the septic infection.
The researchers say clinical studies are needed to assess whether PSM-mec affects sepsis in people and thus can be a target for therapeutics. They also are investigating whether related toxins found in methicillin-susceptible S. epidermidis and S. aureus have a similar function.