WHILE one strain of Staphylococcus aureus may be making a comeback (see above), others are being blamed for triggering a particularly unpleasant illness.
Purpura fulminans is the term used to describe extensive clotting of blood within the blood vessels, and the resulting death of soft tissue, often leading to organ failure and amputations. It is most commonly a complication of infections by the bacterium Neisseria meningitidis, which fortunately are rare.
But Patrick Schlievert鈥檚 team at the University of Minnesota has described 14 cases of purpura fulminans apparently triggered by respiratory infections of S. aureus. In a few the culprit was an MRSA superbug 鈥� one of the strains of S. aureus resistant to the antibiotic methicillin. Half of the patients were infected in hospital, and almost all of them died. Five cases that occurred in the Minneapolis-St Paul area in the past four years are described in an article published online in Clinical Infectious Diseases, and Schlievert鈥檚 team has since identified another nine cases.
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Schlievert thinks the illness is caused by S. aureus strains that produce particularly large amounts of toxins known as superantigens. 鈥淭hese strains make anywhere from 10 to 100 times more superantigen than other staph strains,鈥� he says. That might provoke a massive immune response, resulting in purpura fulminans and toxic shock.
And because S. aureus infections are on the increase, Schlievert believes that staphylococcal purpura fulminans could become increasingly common. He warns that there might be tens of thousands of cases in the next few years.
But not all experts are convinced it is a rapidly growing problem, or that staph superantigens are to blame. Henry Chambers of the University of California, San Francisco, a leading expert on staphylococcal infections, says it is too early to jump to conclusions. What鈥檚 more, he points out that only a few people might be susceptible to purpura fulminans, because of their genes or an acquired immune response.
