CDC issues new rules for combating MRSA ethicillin-resistant staph in check

Methicillin-resistant staph infections have entered the community, posing a bigger challenge for health-care providers. The CDC outlines what to do.

Methicillin-resistant Staphylococcus aureus (MRSA), long recognized as a problem in health-care settings, is increasingly prevalent in the community. A 2004 survey of 11 emergency departments around the country found the organism responsible for 60% of skin infections that were cultured (N Engl J Med. 2006;355:666-674).

“In all but one region, it was the most common pathogen,” says Rachel J. Gorwitz, MD, MPH, medical epidemiologist in the Division of Healthcare Quality Promotions of the CDC and lead author of the recently issued Strategies for Clinical Management of MRSA in the Community: Summary of an Experts' Meeting Convened by the Centers for Disease Control and Prevention. While not an official guideline, this paper represents the latest information the CDC has on community-associated MRSA.

Keep a high index of suspicion

The most basic recommendation is to include MRSA in the differential diagnosis of skin and soft-tissue infections (its most common presentation) as well as in other conditions compatible with S. aureus infection, such as sepsis syndrome, osteomyelitis, and severe pneumonia.

It is important to culture specimens from all abscesses and purulent skin lesions, particularly those that are severe or possibly linked to a cluster of cases, according to the CDC. Not only can results assist in managing the individual patient, routine culturing will provide information about community prevalence of MRSA (and perhaps of organisms resistant to other antibiotics as well) that will be useful in clinical decision-making.

MRSA infections present no differently than those caused by methicillin-susceptible S. aureus, notes Dr. Gorwitz. “But anecdotally, people are seeing MRSA infections that are worse and spread more rapidly than those of susceptible organisms.”

Treatment: Back to the basics

The diagnosis of MRSA infection, accordingly, cannot be made on clinical grounds, and for most patients, antibiotic resistance makes no difference in initial treatment. “Perhaps the most important message is to remind providers that the primary treatment for purulent skin infections is incision and drainage, and oftentimes this is enough,” Dr. Gorwitz states.

This approach will avoid unnecessary use of antibiotics, which will benefit both the patient—less risk of adverse events—and the community, by preventing the development of resistant pathogens, she notes.

FIGURE 1. Treatment of methicillin-resistant Staphylococcus aureus (MRSA)

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Empiric antibiotic treatment is sometimes indicated initially along with incision and drainage (Figure 1). Criteria include the size of the lesion and degree of surrounding redness; the presence of cellulitis; indications, such as fever, of systemic infection; and comorbidities that compromise immune function, such as diabetes mellitus or neoplastic disease. Antibiotics may be reasonably prescribed from the outset for very old or young patients, the Strategies suggest.

In other cases, the addition of an antimicrobial is the usual next step when response to incision and drainage is insufficient. The results of culture, when available, should guide antibiotic selection. If no results are available, take into account susceptibility data for the community when choosing. In areas where the prevalence of MRSA is low, a beta-lactam antibiotic is reasonable for mild-to-moderate illness. When, as is the case in many regions, resistant organisms are more common, the choice becomes complex. (There is no absolute threshold, but some experts have suggested 10%-15% as appropriate.)

Controlled data to define optimal treatment regimens for MRSA infection are lacking; among the proposed agents appropriate in primary care are clindamycin; the tetracyclines, including doxycycline and minocycline; and trimethoprim-sulfamethoxazole (TMP-SMX). “There are advantages and disadvantages to each of these agents,” the CDC notes.

Clindamycin has FDA approval for serious S. aureus infections, and doxycycline for S. aureus skin infections, but neither agent is approved specifically for MRSA. TMP-SMX is not indicated for any staphylococcal infection, but reports have documented its efficacy in some MRSA cases.

Although FDA-approved for S. aureus skin infections, the CDC considers fluoroquinolones and macrolides “less-than-optimal”options. MRSA is often resistant to macrolides as well as to beta-lactam antibiotics, and these strains “are adept at developing fluoroquinolone resistance.”

When community susceptibility patterns are known, antibiotic choice should take them into account. Severe staphylococcal infections are best treated with IV antibiotics, and vancomycin is the agent of choice when MRSA is a distinct possibility. Some experts recommend a combination regimen including nafcillin or oxacillin for very ill patients, the increased risk of toxicity notwithstanding. Consultation with an infectious disease specialist is indicated in any case.

Prevention

Both the patient and the caretaker can limit the spread of MRSA infection (and skin and soft-tissue infections generally). Among the key prevention steps recommended are these: Cover draining wounds with clean, dry bandages. Clean hands regularly with alcohol-based hand gel or soap, particularly after touching infected skin or items that have come in contact with it. Do not share possibly contaminated items, such as towels, clothing, bedding, and bar soap, and promptly launder clothing that has been in contact with the wound. Avoid activities that involve skin-to-skin contact with the uncovered wound. Use a product that specifies activity against S. aureus to clean environmental surfaces that come into contact with the skin.

Question patients about similar infections in household and other close contacts. Local public-health authorities should be notified of possible outbreaks that extend beyond the home environment.

Efficacy data are lacking for decolonization with agents like nasal mupirocin and antiseptic body washes. But decolonization may be appropriate (in cases in which standard prevention measures have proven inadequate) for patients with multiple recurrences of MRSA infection and for members of a household or other well-defined group in which transmission is ongoing. Courses of decolonization regimens should be short to forestall the development of resistance, and administered simultaneously if multiple individuals are involved.

The Strategies advocate consultation with an infectious disease specialist when considering decolonization and with the local public-health department if infection extends to larger cohorts like athletic teams, classrooms, or group homes. For further information, see the full text of Strategies for Clinical Management of MRSA in the Community: Summary of an Experts' Meeting Convened by the Centers for Disease Control and Prevention, which is available online at: www.cdc.gov/ncidod/dhqp/pdf/ar/CAMRSA_ExpMtgStrategies.pdf (accessed May 17, 2007).

Mr. Sherman is a medical writer in New York City.

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