Alternative antibiotics offer slim
comfort as potent strain returns.
11 October 2002
HELEN PEARSON
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| New antibiotics to combat
resistant strains need to be fast-tracked. |
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A drug-resistant superbug has resurfaced, doctors announced
today, leaving researchers scrabbling for the next line of
antibiotic defence.
The rogue Staphylococcus aureus bacteria, identified in the foot
ulcer of a Pennsylvania patient, are resistant to vancomycin, one of
the last lines of antibiotic defence1.
More cases were widely anticipated after reports of the first
such strain earlier this year2.
Today's announcement coincided with confirmation of the case by
the US Centers for Disease Control and Prevention in Atlanta,
Georgia.
The finding fuels an intensifying search for next-generation
drugs to control life-threatening hospital infections. Michael Rybak
and his colleagues at Wayne State University in Detroit, Michigan,
recently tested the first vancomycin-resistant S. aureus (VRSA)
strain, taken from a Michigan patient's wounds, against some of the
newest antibiotics in the drugs arsenal.
Two drugs, daptomycin, which is under development, and the
recently released quinupristin-dalfopristin, killed more than 99% of
the bacteria, the researchers found. "It gives us a little level of
comfort," says Rybak. He presented his results at the Interscience
Conference on Antimicrobial Agents and Chemotherapy in San Diego
late last month. Linezolid, another relatively new antibiotic, only
curbed the growth of VRSA, they found.
Rybak and his team mimicked severe infection in a wound by
growing high concentrations of VRSA in a matrix like a blood clot.
They treated these for three days with doses equivalent to those
given to patients.
"It is reassuring," says George Eliopoulos, who studies
antibacterial agents at Harvard Medical School in Boston, "but I
wouldn't breathe a total sigh of relief." He is concerned that the
bacteria will also acquire resistance to the new drugs. S. aureus
strains immune to linezolid and quinupristin-dalfopristin have
already been reported, despite both being used for less than three
years.
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If these strains explode we're gonna have a major
problem
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David Snydman
Tufts-New England Medical Center
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Bacteria may find it harder to fight daptomycin, however, because
it operates in a different way to many standard antibiotics. Rather
than stopping bugs growing, daptomycin kills them by puncturing the
cell membrane and letting the contents leak out. "Resistance will
emerge but it won't be soon," predicts Frank Tally of Cubist
Pharmaceuticals in Lexington, Massachusetts, which licenses the
drug.
Cubist Pharmaceuticals plans to file an application for
daptomycin's approval with the Food and Drug Administration this
year. This might be rubber-stamped by the end of 2003 at the
earliest. "There's clearly a need for it to be fast-tracked," says
David Snydman who has carried out studies on the drug at the Tufts
University School of Medicine in Boston, Massachusetts.
According to Snydman, daptomycin is by far the most promising of
the antibiotics being developed to tackle VRSA. Even so, he says, if
the bacteria beat the drugs "we're gonna have a major problem". |
