A Closer Look At The New IDSA Guidelines For MRSA In Skin And Soft Tissue Infections

Warren S. Joseph DPM FIDSA

After an extended, deliberative writing and review process, the brand new Infectious Diseases Society of America (IDSA) clinical practice guidelines on the treatment of methicillin resistant Staphylococcus aureus (MRSA) have finally been published (full text at http://cid.oxfordjournals.org/content/early/2011/01/04/cid.ciq146.abstract ).

I really feel that this document is a must read for anyone interested in treating infections of the lower extremity. For right or wrong, clinical practice guidelines are frequently held out to represent the “standard of care” and this document will be no exception. In fact, these guidelines include an excellent disclaimer, which frankly states that adherence to the guidelines is “… voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient’s individual circumstances.”

Overall, this is an excellent piece of work and kudos goes out to lead author Catherine Liu, MD, of the University of California, San Francisco, and the committee. Sitting on an IDSA Guidelines committee, I understand the process. It could not have been easy to come to consensus particularly in an area of infectious disease that is changing so rapidly and where there is the potential for so much controversy.

Although much of the document pertains to infections other than skin/skin structure and bone/joint, I still feel it is important to list those points from the Executive Summary that could have direct impact on a lower extremity infection practice. With all of the new IDSA Guidelines, the required format is “question, answer, evidence summary.” I will pick out parts of those that apply to our practice and would ask that you please read the entire document for the complete picture. As you would expect, I will not resist adding my two cents. My comments will appear in italics.

Question I: What is the management of skin and soft tissue infections in the era of community-associated MRSA?
1. For a cutaneous abscess, I&D is the primary treatment. For simple abscesses or boils, I&D alone is likely to be adequate. I have covered this subject in the past. The treatment of a CA-MRSA simple (usually defined as

2. Antibiotic therapy is recommended for abscesses associated with the following conditions: severe or extensive disease (e.g., involving multiple sites of infection), or rapid progression in presence of associated cellulitis, signs and symptoms of systemic illness, associated comorbidities or immunosuppression, extremes of age, abscess in an area difficult to drain (e.g., face, hand and genitalia), associated septic phlebitis, and lack of response to incision and drainage alone. This point is valuable in that it actually spells out those conditions in which one should consider antibiotics adjunctive to the I&D.

3. For outpatients with purulent cellulitis (e.g., cellulitis associated with purulent drainage or exudate in the absence of a drainable abscess), empirical therapy for CA-MRSA is recommended pending culture results. Empirical therapy for infection due to beta-hemolytic streptococci is likely to be unnecessary. Five to 10 days of therapy is recommended but should be individualized on the basis of the patient’s clinical response. This is an interesting point in that it differentiates “purulent” cellulitis from “non-purulent” cellulitis (see next point). Frankly, I am not certain that I have seen that in the past. Most of what we are seeing in the lower extremity is the purulent variety but, as I write this, I have a patient in the hospital with venous insufficiency and a significant cellulitis of her leg, but no pus. Sure enough, cultures of the clear drainage taken just grew Group B, beta-hemolytic Strep.

4. For outpatients with non-purulent cellulitis (e.g., cellulitis with no purulent drainage or exudate and no associated abscess), empirical therapy for infection due to b-hemolytic streptococci is recommended. The role of CA-MRSA is unknown. For the patient I just mentioned above, she had started empirically on vancomycin from the emergency department. She did not improve to my satisfaction so we added piperacillin/tazobactam and had remarkable improvement within 24 hours. I stopped the vancomycin.

5. For empirical coverage of CA-MRSA in outpatients with SSTI, oral antibiotic options include the following: clindamycin, trimethoprim-sulfamethoxazole (TMP-SMX), a tetracycline (doxycycline or minocycline) and linezolid. If coverage for both beta-hemolytic streptococci and CA-MRSA is desired, options include the following: clindamycin alone or TMP-SMX or a tetracycline in combination with a beta-lactam (e.g., amoxicillin) or linezolid alone. This point really just lists the oral antibiotic choices we knew we had all along. I would direct you to the document’s “evidence summary” to see how little actual data there is backing any of this though. Furthermore, I am not as enamored with TMP/SMX as the recommendations in these guidelines and tend to prefer using doxycycline or minocycline.

6. The use of rifampin as a single agent or as adjunctive therapy for the treatment of SSTI is not recommended. I agree and do not use rifampin. As you will see in the osteomyelitis and prosthetic joint section, these guidelines are very “pro” rifampin despite what I feel is a lack of any significant evidence.

7. For hospitalized patients with complicated SSTI (cSSTI; defined as patients with deeper soft tissue infections, surgical/traumatic wound infection, major abscesses, cellulitis and infected ulcers and burns), in addition to surgical debridement and broad-spectrum antibiotics, empirical therapy for MRSA should be considered pending culture data. This point is big. They are recommending that pretty much all patients admitted with cSSTI, which would translate into almost all admitted patients, start on anti-MRSA therapy. There is no leeway given for local/regional variations in incidence. Sure, most of us have been doing this but, frankly, in the past six months to a year, most of our admitted patients are not growing MRSA at this point. I have actually started going back to escalation (no MRSA empiric coverage) therapy in some cases.

Given the importance of this document, I would rather break down the discussion into shorter, hopefully more easily digestible portions. In a future blog, I will comment on the bone and joint recommendations, which include osteomyelitis, septic arthritis and implant related infections along with the recommendations for vancomycin dosing and monitoring.

Editor’s note: This blog was originally published at http://www.leinfections.com/category/antibiotics/ and has been adapted with permission from Warren Joseph, DPM, FIDSA, and Data Trace Publishing Company. For more information about the Handbook of Lower Extremity Infections, visit www.leinfections.com/ .

Add new comment