Drug fells new bug, but resistance is appearing
Tests show Synercid effective against VISA strain
The emergence of intermediate vancomycin resistance in Staphylococcus aureus in Japan has raised the specter of untreatable infections, but there is at least one arrow left in the quiver should the first cases begin appearing here, Hospital Infection Control has learned.
The drug Synercid manufactured by Rhone-Poulenc Rorer in Collegeville, PA was effective against the Japanese strain of vancomycin-intermediate S. aureus (VISA) that was sent to the Centers for Disease Control and Prevention for confirmation. The drug is generically known as streptomycin, which was used to successfully clear the first infection in Japan.
It is currently available in the United States only on a compassionate-use basis, primarily for patients infected with vancomycin-resistant enterococci (VRE), but is nearing final approval by the Food and Drug Administration.
"It has been used widely in the United States for VRE and it has also been used for staph infections in Europe, and it appeared to work well," says Fred Tenover, PhD, chief of the CDC nosocomial pathogens laboratory branch. "We have tested it here and the drug is effective in inhibiting this [VISA] strain in the laboratory."
Sharon Gray, MS, compassionate use program director at Rhone-Poulenc Rorer, said phase III clinical trials have been concluded, and data on efficacy and toxicity are expected to be submitted to the FDA by next month.
"They anticipate only a six-month turnaround because the drug has been fast-tracked against VRE," she says. "So it actually would be marketed for VRE first and it would be out probably by February or March of next year."
The drug could prove an important weapon against the intermediate-resistant strain, because clinicians may not have the option of simply increasing levels of vancomycin to overcome the resistance.
"With a lot of drugs you can simply increase the dose and get strains in the intermediate category, but you can’t do that with vancomycin because it becomes toxic," Tenover says.
Moreover, the CDC research suggests that Synercid could be effective even against fully resistant strains because it attacks S. aureus differently from vancomycin.
"Because it affects a totally different site it is a totally different class of drug there is no reason to think it would not be effective," Tenover says.
Still, in yet another reminder that no single drug will prove a panacea, there are already the first signs of Synercid resistance in enterococci and staphylococci, Gray says, noting that both intermediate and full resistance have been reported by investigators.
"There is not a lot, but it is there," she says.
Thus far, Synercid is proving effective in clearing VRE and MRSA infections about 60% to 70% of the time without major side effects, she adds.
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