For part two of this posting on the new Infectious Diseases Society of America (IDSA) methicillin resistant Staphylococcus aureus (MRSA) guidelines, I would like to comment on some of the executive summary points made about MRSA bone and joint infections. I will use a similar format as before with posting the actual text and then adding my comments in italics.
Unlike the previous post (http://bit.ly/e4bsdr  ), I have decided to keep in the guideline’s evidence gradings so you can determine for yourself whether you feel the recommendations are of a high enough level of medical evidence. I have also left the numbering intact so you can compare it to the original document found at http://cid.oxfordjournals.org/content/early/2011/01/04/cid.ciq146.abstract  ).
V. What is the management of MRSA bone and joint infections?
36. Surgical debridement and drainage of associated soft tissue abscesses is the mainstay of therapy and should be performed (whenever feasible) (A-II). This is a recommendation made with a high level of evidence, which supports the common thinking that surgery is important when practical. I added the “when feasible” because of the increasingly strong body of evidence that supports “medical” or non-surgical therapy of osteomyelitis. That being said, those studies have not specifically looked at MRSA. Whether surgery is any more important in MRSA osteomyelitis in comparison to other organisms has not been established.
37. The optimal route of administration of antibiotic therapy has not been established. Parenteral, oral or initial parenteral therapy followed by oral therapy may be used depending on individual patient circumstances (A-III). Much like I have lectured and written on in the past, the whole “six weeks of IV therapy” thing has never been based in any good human evidence. In fact, newer and stronger evidence points to alternative regimens like oral therapy alone or a short course of parenteral therapy followed by oral antibiotic therapy as effective. I am pleased to see this recognized in this document.
38. Antibiotics available for parenteral administration include IV vancomycin (B-II) and daptomycin 6 mg/kg/dose IV once daily (B-II). Some antibiotic options with parenteral and oral routes of administration include the following: TMP-SMX 4 mg/kg/dose (TMP component) twice daily in combination with rifampin 600 mg once daily (B-II), linezolid 600 mg twice daily (B-II) and clindamycin 600 mg every 8 h (B-III).
39. Some experts recommend the addition of rifampin 600 mg daily or 300–450 mg PO twice daily to the antibiotic chosen above (B-III). For patients with concurrent bacteremia, rifampin should be added after clearance of bacteremia. This is where it gets interesting. Yes, I have known about the concept of adding rifampin to other antibiotics to treat MRSA (never use it single agent as resistance develops rapidly) but I have never used it nor felt it was all that necessary. I am surprised to see it mentioned numerous times in this document. It is listed not only here but also in the “osteoarticular device” related infection section.
Notice the level B-III rating. This means a “moderate level of evidence and a recommendation based on expert opinion, clinical experience … ,” not randomized controlled trials. In fact, if you look at the “evidence summary” section that covers rifampin, I still am not terribly convinced. I will have to see if I start incorporating it into my treatment.
40. The optimal duration of therapy for MRSA osteomyelitis is unknown. A minimum eight-week course is recommended (A-II). Some experts suggest an additional one to three months (and possibly longer for chronic infection or if debridement is not performed) of oral rifampin-based combination therapy with TMP-SMX, doxycycline-minocycline, clindamycin, or a fluoroquinolone, chosen on the basis of susceptibilities (C-III). Again, add rifampin to oral regimens. This recommendation contains even a lower evidence rating of “C,” meaning “poor evidence to support a recommendation.”
41. Magnetic resonance imaging (MRI) with gadolinium is the imaging modality of choice, particularly for detection of early osteomyelitis and associated soft-tissue disease (A-II). Erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP) level may be helpful to guide response to therapy. There is nothing particularly remarkable here. I left it in for the sake of completeness.
In the next blog, I will discuss what the IDSA MRSA guidelines recommend on vancomycin dosing. I welcome your comments about these blogs on the new IDSA MRSA guidelines.
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/  .