Journal of Antimicrobial Chemotherapy Paper Supports Additional Role for Cethromycin as Potential Treatment for Infections Caused by Community- Associated Methicillin Resistant Staphylococcus Aureus

CHICAGO, June 25 /PRNewswire-FirstCall/ -- Advanced Life Sciences Holdings, Inc. , a biopharmaceutical company engaged in the discovery, development and commercialization of novel drugs in the therapeutic areas of infection, cancer and respiratory diseases, today announced that the Journal of Antimicrobial Chemotherapy has published a paper entitled 'Susceptibility of 170 Isolates of the USA300 clone of MRSA to macrolides, clindamycin and the novel ketolide cethromycin.' The published results demonstrate that cethromycin is highly active in vitro against community- associated methicillin resistant Staphylococcus aureus (CA-MRSA), which is resistant to macrolides and other antibiotics. The results suggest that cethromycin exhibits the ability to treat infections caused by CA-MRSA, further supporting the potential of the drug as a front-line treatment for respiratory tract infections.

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Methicillin-resistant Staphylococcus aureus, also called MRSA, is a pathogen that is not killed by many of the antibiotics doctors most commonly prescribe for the treatment of infections. An October, 2007 Centers for Disease Control and Prevention (CDC) report cited that about 94,000 Americans were infected by MRSA in 2005, and this superbug killed more patients than AIDS by contributing to nearly 19,000 deaths that year. Nearly 14% of these infections were due to exposures in the community. Until the late-1990s, MRSA mainly affected patients in hospitals and other healthcare settings. Since that time, a new strain of MRSA has emerged. This new strain is called community-associated MRSA (CA-MRSA), and has rapidly become one of the most common causes of skin and soft tissue infections among otherwise healthy people in the community. Staphylococcus aureus and CA-MRSA are causative pathogens for respiratory tract infections such as community acquired pneumonia (CAP). The CA-MRSA strain can attack and destroy white blood cells that normally help fight infections and can be even more aggressive than the hospital associated MRSA infections. Although the early strains of CA-MRSA strains were susceptible to most antimicrobials, bacterial resistance has increased, creating a need for new antibiotics that can cover the emerging deadly CA-MRSA strain.

The aim of the study reported in the paper was to compare the antimicrobial activity of cethromycin with three other macrolides (azithromycin, clarithromcin and erythromycin) and one lincosamide (clindamycin) against the 170 MRSA USA300 isolates that are contained in the Center for Biological Defense collection at the University of South Florida.

Cethromycin was shown to be effective against all 170 isolates, achieving an MIC range of < / = 0.002-0.125 mg/L, whereas the MIC50 and MIC90 were both < / = 0.002 mg/L. In addition, cethromycin demonstrated a MBC range of < / = 0.002-1.0 mg/L, with the MBC50 of < / = 0.002 mg/L and the MBC90 of < / = 0.008 mg/L. Of the 170 CA-MRSA isolates, 169 (99.4%) were intermediate or resistant to at least one macrolide. In contrast, 164 (96.5%) isolates were susceptible to clindamycin. Only six (3.5%) isolates demonstrated either constitutive resistance [4 (2.4%)] or inducible resistance [2 (1.2%)] to clindamycin. Against 10 erythromycin-susceptible isolates, the cethromycin MIC and MBC ranges were < / = 0.002-0.008 mg/L, compared with the MIC range of < / = 0.002-0.25 mg/L and MBC range of < / = 0.002-1.0 mg/L obtained with the erythromycin-resistant isolates. MIC50 and MBC50 values, as well as MIC90 and MBC90 values, did not change regardless of erythromycin susceptibility. Six isolates proved resistant to both erythromycin and clindamycin, against which cethromycin MIC and MBC ranges were < / = 0.002-0.06 mg/L.

David A. Eiznhamer, Ph.D., Executive Vice President of Clinical Development at Advanced Life Sciences, a co-author of the paper noted, "The susceptibility of CA-MRSA to cethromycin is especially important, as most of the isolates in this study were resistant to one or more macrolides. The growing resistance of pathogens to macrolide-based treatments is increasing the demand for new antibiotics that can overcome this resistance. We believe this study demonstrates that cethromycin could prove very beneficial in the treatment of respiratory tract infections, including those caused by pathogens such as CA-MRSA."

About Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) is a type of bacteria that is resistant to certain antibiotics. Staph infections, including MRSA, occur most frequently among persons in hospitals and healthcare facilities, such as nursing homes and dialysis centers, who have weakened immune systems. MRSA infections that occur in otherwise healthy people who have not been recently hospitalized or who have undergone a medical procedure such as dialysis or surgery, are known as community-associated (CA-MRSA) infections. These infections are usually skin infections, such as abscesses, and boils but CA-MRSA can also cause respiratory infections such as community acquired pneumonia.