Researchers from the Hershey Medical Center announced the publication of research demonstrating that the antibiotic fusidic acid is active against MRSA strains isolated from cystic fibrosis (CF) patients. In addition, fusidic acid did not antagonize the activity of two antibiotics, tobramycin and amikacin, that are commonly used in CF patients to treat P. aeruginosa and B. cepacia infections. These results indicate the important role that fusidic acid may play in treating CF patients with MRSA lung infections. The report was published in the May 2011 issue of Antimicrobial Agents and Chemotherapy (volume 55(5)).
The study tested fusidic acid plus other agents against 40 MRSA strains isolated from CF patients. Fusidic acid’s affect on activity of tobramycin or amikacin against P. aeruginosa and B. cepacia strains isolated from CF patients was also tested to determine if co-administration of fusidic acid would antagonize the activity of these two antibiotics commonly used in this patient population. The investigators found that fusidic acid showed potent activity against MRSA isolates with an MIC90 of 0.25 ug/ml compared to MIC90s of 1 ug/ml for vancomycin, teicoplanin and daptomycin, 0.25 ug/ml for tigecycline and 2 ug/ml for linezolid. Fusidic acid also showed no antagonism of either tobramycin or amikacin activity as measured by an in vitro time-kill analysis.
P. aeruginosa is the best known organism colonizing the lung of CF patients. More recently, S. aureus and MRSA have become more significant lung pathogens in these patients. MRSA is a relatively common respiratory infection in CF patients in North America, with documented detection rates of 4.4 to 6.9 percent. MRSA infections result in increased mortality in these patients with a mortality rate among MRSA positive patients of 27.7 deaths/1000 patient years compared to 18.3 deaths/1000 patient years for patients without MRSA isolates. Therefore, a safe and effective treatment that could be used chronically for these infections would be of value to these patients.
“Cystic fibrosis patients often face challenging bacterial infections as a result of their disease,” said Klaudia Kosowska-Shick Ph.D., Department of Pathology, Hershey Medical Center and senior author of the paper. “MRSA causes serious lung infections in these patients and new therapeutic options, particularly oral agents, would be valuable additions. Fusidic acid’s in vitro activity against these U.S.-based strains, its lack of effect on tobramycin and amikacin activity and results from clinical studies in Europe indicating that oral fusidic acid can treat S. aureus infections in CF patients suggest that it may be a promising therapeutic candidate in these patients”.
Prabhavathi Fernandes, Ph.D., chief executive officer of Cempra added, “Our company is developing a novel dosing regimen of fusidic acid, named TAKSTA, that incorporates a PK-PD-based loading dose to maximize efficacy and minimize resistance development. In fact, the Institute for Clinical Pharmacodynamics (ICPD) showed that a loading dose of fusidic acid could overcome past issues of resistance development of this drug. This published work highlights the versatility of the compound to potentially treat not only serious acute bacterial skin and skin structure infections, in which we have completed Phase 2 clinical trials in the U.S., but also its potential utility for oral treatment in other more chronic infections in diverse patient populations, such as cystic fibrosis and osteomyelitis patients.”
Date: April 28, 2011
Source: Cempra Pharmaceuticals www.cempra.com
