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Researchers at Harvard Medical School describe in The Lancet medical
journal this week how an 85 year-old man on dialysis came down with a staph
infection in the lining of his intestines that was not vulnerable to the new
drug, Zyvox. It is the first report of staph resistance to the medicine.
Experts said that while the finding is disappointing, it isn't
surprising - they have learned to expect the unpredictable from crafty
bacteria - and the drug still should be able to help many people.
``It's a heads up that you have to keep an eye on it,'' said Dr. Mary
Jane Ferraro, director of microbiology at Massachusetts General Hospital in
Boston, who found the resistant strain. ``It was only a matter of time.
Whether or not it's going to become prevalent, or whether this is going to
be a rare thing, we can't predict.''
Staphylococcus aureus is considered the most successful of all
bacterial germs because it produces such a wide range of infections in so
many people.
It is the leading cause of infections acquired in hospitals worldwide
and causes ailments ranging from boils and urinary tract infections to toxic
shock syndrome and pneumonia.
Half of all staph that circulates in hospitals is resistant to
meticillin, the standard drug used to treat it. Now it is developing
resistance to the main reserve drug, the antibiotic vancomycin.
In a bid to slow resistance, the U.S. Centers for Disease Control and
Prevention now advise doctors to refrain from using vancomycin unless
absolutely necessary. Consequently, Zyvox is becoming more widely used in
the
United States.
``We may discover, within the course of the next few months that
(using
Zyvox so widely) is untenable, but we don't know at this stage,'' said Dr.
Roger Finch, a professor of infectious diseases at Nottingham University in
England who was involved in the testing of the new drug.
Zyvox is a synthetic chemical designed to fight germs at a different
point in their life cycle than any other antibiotic. It stops bacteria from
making protein, which in turn stops their growth, so the body's immune
system
can step in and finish them off.
Known chemically as linezolid, it is the first in a long-awaited class
of antibiotics called oxazolidinones and has arrived just as bacteria are
becoming increasingly resistant to vancomycin.
Zyvox was released in the United States in April 2000 and in Britain
in
January. It is not yet available in other countries. So far, 80,000 patients
have received it, according to the drug's maker, Pharmacia Corp.
``It's frustrating. So much effort goes into the development of these
drugs - huge resources - and one hoped that we would have had a number of
years of successful use of this agent,'' because it was different from older
antibiotics, Finch said. ``It's disturbing and it means we've got to keep
looking for new approaches.''
A handful of drugs belonging to this new class are in the pipeline,
experts said.
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