New Study Reveals Promise Of Linezolid For Diabetic Infections

By Brian McCurdy, Associate Editor

In the wake of increasing threats of resistant bacteria strains such as MRSA, new data presented at the 40th Annual Meeting of the Infectious Diseases Society of America provides some hope. Researchers revealed that linezolid may have promise in treating diabetic foot infections caused by bacteria such as Staphylococcus aureus. According to the results of the study, which involved over 350 patients at U.S. and European sites, 81.3 percent of the linezolid patients were “clinically cured,” compared to 71.3 percent of patients who received a standard aminopenicillin combination. Benjamin A. Lipsky, MD, a principal investigator for the study, says it indicates linezolid is effective in treating these infections and is at least as effective as the most commonly used antibiotics, ampicillin/sulbactam (IV) and amoxicillin/clavulanate (oral). He says he is encouraged by these findings. “(The findings) suggest that linezolid (Zyvox, Pharmacia) may be an important addition to currently available treatments for diabetic foot infections, particularly those caused by the MRSA that are becoming increasingly common,” explains Dr. Lipsky, a Professor of Medicine at the University of Washington School of Medicine. An Oral And Outpatient Alternative? Adam Landsman, DPM, PhD, also believes that linezolid has potential in the treatment of these patients. “In particular, diabetic foot ulcer patients with infected ulcers will benefit from the availability of an IV strength medication given on an oral and outpatient basis,” says Dr. Landsman, a member of the adjunct faculty at the Northwestern University School of Medicine. “The best way to prevent serious infections with organisms like MRSA is to avoid potential exposure to nosocomial infections.” Dr. Lipsky says the study also showed oral therapy with both linezolid and the aminopenicillins/beta-lactamase inhibitors was as effective as intravenous and that outpatient therapy was as effective as inpatient. When patients have a suspected or proven infection with resistant gram-positive organisms, especially methicillin-resistant Staph aureus, linezolid would be an appropriate choice, according to Dr. Lipsky, the Director of the General Internal Medicine Clinic of the VA Puget Sound Health Care System in Seattle. According to Pharmacia, Zyvox is indicated for complicated skin and skin structure infections caused by Staphylococcus aureus (both methicillin-resistant and -susceptible strains), Streptococcus pyogenes and Streptococcus agalactiae. Dr. Landsman uses linezolid for patients whom he is on the fence about in regard to admission vs. outpatient treatment. When a patient presents with a red, swollen foot but does not clearly need surgical debridement, Dr. Landsman says he will attempt three to four days of treatment on an outpatient basis with linezolid. “If they respond, I keep them out of the hospital and continue with oral treatment,” notes Dr. Landsman. “If they don’t, then I admit them for surgical debridement. Our success rate using this approach has been outstanding.” There are some caveats to keep in mind. According to the study, more Zyvox-treated patients had drug-related adverse events, although researchers noted that these were mostly hematologic and gastrointestinal in nature, were mild to moderate in intensity and reversible. Addressing The Resistance Issue Dr. Lipsky also notes that while “linezolid appears to be relatively resistant to the development of resistance,” there have been a couple of cases. He says these patients are typically those who have underlying immune deficiencies, co-morbidities (e.g., renal failure), foreign bodies in place (e.g., indwelling catheters or prostheses) or those who have received prolonged therapy. Overall, the rise of resistant bacteria strains continues to be a major problem, according to Drs. Lipsky and Landsman. The Centers for Disease Control and Prevention (CDC) recently announced the discovery of a second case of VRSA and Dr. Lipsky calls MRSA “an increasing problem all over the world.” Dr. Lipsky notes that, in many locations, 30 to 50 percent of S. aureus isolates are now methicillin-resistant. In his hospital, the number is 50 percent and 50 to 60 percent are also resistant to erythromycin and clindamycin. Further, Dr. Lipsky adds that some data suggest infections with MRSA are associated with higher rates of amputation than those caused by other organisms.

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