The bacterium Staphylococcus aureus, cause of the common skin infection bullous impetigo, produces a toxin that attacks a protein highly specific for cell-to-cell binding in the outermost layer of the skin, according to a new study funded by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Breakup of this protein, say the researchers, not only brings about the characteristic blistering of the infection, but gives the bacterium "an exquisitely specific mechanism to circumvent the skin's protective barrier and spread further."
The University of Pennsylvania's John Stanley, M.D., and his colleagues there and at Japan's Keio University found that the toxin, exfoliative toxin A, causes impetigo's blisters when it breaks up the protein Desmoglein 1 (Dsg1), which is responsible for a specialized type of binding in epidermal skin cells. Only the Dsg1 protein is broken up, say the scientists, and not other closely related proteins. The consequent breakdown in skin cell adhesion gives Staphylococcus a way to proliferate and cause more damage.
The researchers suspected Dsg1 was the toxin's target because it is also the target of autoantibody attacks in pemphigus follaceus, a blistering skin disorder with similar cellular characteristics. The work was carried out in cell culture, mouse skin and with recombinant Dsg1, and the results emphasize the importance of the protein's functioning to healthy, protective skin. The major therapy for the infection will continue to be antibiotics, say the researchers, even though agents that fight protein breakup might help prevent the spread of the bacterium.
"Dr. Stanley's work reminds us again of the elegant specificity of many of the biological systems we deal with in studying disease," said NIAMS Director Stephen I. Katz, M.D., Ph.D., "and of how very close our basic discoveries can be to a clinical outcome."
Bullous impetigo is a common infection among children aged 2 to 6. The findings also extend to its more generalized form, staphylococcal scalded-skin syndrome. The research is reported in the November 2000 issue of the journal Nature Medicine. It was also supported by Grants for Research on Specific Diseases from the Ministry of Health and Welfare of Japan.
Amagai M, Matsuyoshi N, Wang ZH, Andl C, Stanley JR. Toxin in bullous impetigo and staphylococcal scalded-skin syndrome targets desmoglein 1. Nature Medicine 2000;6(11):1-3.