Now We Have 'Flesh-Eating Pneumonia'
By Amy Norton

NEW YORK (Reuters Health) - Staph bacteria carrying a specific toxin can cause a severe, highly lethal type of pneumonia in otherwise healthy children and young adults, according to French researchers.
They have so far linked infection with these toxin-carrying bugs to 29 cases of pneumonia marked by widespread tissue destruction in the respiratory tract. Of the 16 cases they report on in the March 2nd issue of The Lancet, 75% were fatal.
The responsible bacterial toxin, called Panton-Valentine leukocidin (PVL), kills white blood cells. A small percentage of Staphylococcus aureus strains have been found to produce the toxin, according to the new study's authors, led by Dr. Jerome Etienne of the National Reference Center for Staphylococcal Toxemia in Lyon, France.
Infections with Staphylococcus aureus are common and often minor, causing problems such as pimples and other skin conditions. But the bacteria can also spread to the blood and cause serious infections of the bone, heart and other tissue.
Based on their series of cases, the researchers conclude that "pneumonia caused by PVL-positive S. aureus seems to be a specific disease...with a poor prognosis." Because of the extensive destruction it causes in the lungs and other tissue, they have dubbed the illness S. aureus necrotizing (death of living tissue) pneumonia.
It is unclear how common this pneumonia is, Etienne told Reuters Health. But based on the current evidence, he said, "we have the feeling" the incidence is a minimum of one case per 10 million people every year.
Between 1986 and 1998, eight cases of severe pneumonia caused by PVL-carrying Staph were reported in France, all in children and young adults, according to Etienne's team. In the current study, the researchers compared these cases--along with eight more identified in 1999--with cases of pneumonia caused by Staph without the toxin.
These PVL-negative patients were far older, ranging in age from 59 to 81, and typically had underlying conditions such as diabetes and lung disease that put them at higher risk of pneumonia. In contrast, the PVL-positive cases occurred in children, teens and adults in their 20s, none of whom had serious underlying disorders.
The pneumonia itself was different as well. The young patients were more likely to have high fever and cough up blood, the investigators found. Most cases started with a flu-like illness that rapidly progressed to severe pneumonia, with death of white blood cells and tissue destruction in the lungs and throat.
Since these cases, the authors note, 13 more have been diagnosed in their laboratory. In 1999, they add, four US children died of Staph infection, three of whom had symptoms akin to those of necrotizing pneumonia.
Etienne said his team doesn't know why these PVL cases are concentrated in children and young adults, when most cases of Staph pneumonia occur in elderly patients with underlying conditions. One hypothesis, he said, is that some younger people may lack protective antibodies against the infection.
SOURCE: The Lancet 2002;359:753-759.

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