- 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.
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- 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.
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- 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.
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- 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.
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- 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.
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- 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.
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- 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.
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- 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.
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- 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.
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- 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.
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- 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.
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- SOURCE: The Lancet 2002;359:753-759.
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