Guidelines clarify recommended MRSA treatments

February 1, 2011

The first U.S. clinical practice guidelines for treatment of methicillin-resistant Staphylococcus aureus (MRSA) clarify use of antibiotics and devote substantial attention to invasive bacteremia, endocarditis, bone and joint infections, and pneumonia.

Key Points

Recommendations on skin and soft-tissue infections are a small and relatively simple part of the directives, released on Jan. 5.

They were created by the Infectious Diseases Society of America (IDSA) and were reviewed and endorsed by the Pediatric Infectious Diseases Society, the American College of Emergency Physicians and the American Academy of Pediatrics. The collaborative approach is an effort to establish consistency and limit the proliferation of guidelines.

Antibiotics should be used in patients with cellulitis, patients who exhibit signs or symptoms of systemic infections, or in more complicated patients such as those with diabetes or compromised immune function, according to Henry F. Chambers, M.D.

An expert on MRSA and a member of the IDSA guidelines panel, he is chief of the division of infectious diseases at San Francisco General Hospital and a professor of medicine at University of California, San Francisco.

Dr. Chambers laments that so much of the guidance is based upon lower-quality B- and C-level data.

"We felt really hamstrung by the small number of well-done studies and the quality of the data," he says.

One research priority is the question of whether antibiotics are even necessary for treating some of these infections.

"It leads to a lot of gratuitous use," Dr. Chambers says.

Another is addressing the "unbelievably high" treatment failure rate in treating MRSA infections, he says. "And yet none of the new drugs that have come down the pike are any better than what we already have."

Antibiotic resistance

The issue of antibiotic resistance is of greater concern in treating systemic infections than in treating skin infections. Adding to the complication, resistance rates often are not known, can be very localized, and appear to be changing rapidly.

"There is one oral agent that is universally effective as a systemic agent - linezolid - but it is very expensive," Dr. Chambers says. Twenty years ago, the fluoroquinolones occupied that treatment niche, "but we have essentially lost those drugs."

Dr. Chambers says, "The major problem is the inability to use a beta-lactam with confidence that you are covering MRSA. It is the issue of what do you do about other organisms, primarily group A streptococci, that might also be causing the syndrome, and you don't know what the efficacy of these drugs are against these organisms.

"To the extent that resistance continues to be a problem, we are going to need new antibiotics."

Ideally, treatment would be based upon a complete understanding of the organisms in a wound and their resistance profile, if any. But the time delay in obtaining that information and the cost of those tests are a barrier to moving beyond treating empirically.

"Ultimately, as antibiotics become dearer and dearer, rapid diagnostics are really going to be the way to go," Dr. Chambers says. He believes that a true point-of-care rapid diagnostic is 10 to 20 years away. Perhaps the greatest barriers to overcome are vested interests in the status quo and regulatory hurdles, rather than technological or economic impediments.