Methicillin-Resistant Staphylococcus aureus Guidelines: A Myriad of Open Questions

TO THE EDITOR—We read with interest the newly released guidelines for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) by the Infectious Diseases Society of America (IDSA) [1]. It is a long-awaited document that covers many important clinical questions that appear during the day-to-day care of patients. The document is comprehensive in many aspects and reviews critically important infections caused by MRSA [1]. Nevertheless, we have important reservations regarding the context and language in which certain sections of the guidelines were written. The guidelines have multiple points that are in contradiction with prior published guidelines endorsed by the IDSA, and there are other instances in which additional clarifications may be required. In the section about management of bacteremia and infective endocarditis, indications for short-duration (14-day) versus long-duration (4–6-week) bacteremic therapy were outlined. However, the guidelines did not mention factors associated with poor outcomes that are mentioned in the IDSA’s guidelines for management of catheter-related infection, including diabetes, immunosupression, and (in the presence of catheters) thrombophlebitis [2]. There is no mention of the role of community-onset bacteremia, which is associated with an elevated incidence of complications and may warrant a longer duration of therapy [3, 4]. In the section about osteomyelitis, even though the data regarding duration of therapy are poor, the authors suggest a minimum of 8 weeks of therapy. This recommendation is based on the results of 2 studies of patients with vertebral osteomyelitis, among whom the presence of abscesses was common; also, only a limited number of patients underwent drainage. In the article by Priest et al [5], which included data on 40 patients with S. aureus osteomyelitis, 60% of patients had an associated abscess, but only 40% underwent drainage of their abscess. Although cure was more common among patients who received ≥8 weeks of therapy, this finding was not statistically significant (P = .05) [5]. The second article reported the findings of a study involving patients with vertebral hematogenous osteomyelitis due to S. aureus, for whom longer durations of therapy were associated with better outcomes [6]. It is important to note that both articles refer to vertebral osteomyelitis, in which epidural abscess is common and is associated with unique complications and therapies—given the tendency of some physicians to employ a conservative, nonsurgical approach to treating this disease. It is not clear from the guidelines why such findings were generalized to other types of osteomyelitis. Regarding the management of MRSA pneumonia, the authors recommend therapy with either vancomycin or linezolid, and they suggest that the optimal duration of therapy is 7–21 days, on the basis of the duration of therapy used in recent clinical trials [7–9]. Although S. aureus was one of the most frequently isolated pathogens in these studies, most of the studies did not exclusively focus on MRSA. Furthermore, in the MRSA guidelines, no comment was made regarding the influence of the presence of bacteremia in this subset of patients [1]. What would be the optimal regimen for that subset of patients? Or the duration of therapy? These questions are important and should be considered for discussion in subsequent updates to these recommendations.