Community-Associated Methicillin-Resistant Staphylococcus aureus: Is It in Your Community and Should It Change Practice?

Abstract

In this issue of Annals, Frazee et al have reported a phenomenon that many emergency physicians have already experienceddcommunity-associated methicillin-resistant Staphylococcus aureus (MRSA) now appears to be among the most common etiologies of skin and soft tissue infections. This study is a good example of how emergency department (ED) surveillance can be critical for making sentinel observations of community events on the basis of examination of clinically important syndromes. Past reports have noted increased proportions of S aureus isolates that are community-associated MRSA from specimens submitted to microbiology laboratories, but these studies suffer from biases associated with culture acquisition, poorly defined patient groups, and lack of prospective data collection to confirm absence of MRSA risk factors (eg, nursing home residence) in order to establish prevalence rates in otherwise healthy community members. Because this study is from one urban center with a large proportion of higher-risk patients such as intravenous drug users and the homeless, we must be cautious in assuming that its findings can be generalized to other areas. However, considering the increasing reports from various sources and sites, it appears that MRSA may be replacing methicillin-susceptible S aureus (MSSA) as the typical community staphylococcal strain. Antimicrobials that appear to have in vitro activity against US community-associated MRSA isolates include vancomycin, clindamycin, trimethoprim-sulfamethoxazole, rifampin, and linezolid. Most MRSA isolates are resistant to macrolides and quinolones, and many are resistant to tetracyclines. As mentioned by Frazee et al, some macrolide-resistant strains of MRSA have what has been termed ‘‘inducible’’ clindamycin resistance. This is found by the performance of a ‘‘D-test’’ in the microbiology laboratory, a procedure that is not routine in many centers. There have been case reports of treatment failures or recurrences associated with clindamycin therapy for these strains, but it appears that most patients will recover with clindamycin therapy. Concern about inducible clindamycin resistance is probably not a reason to completely avoid clindamycin for skin and soft tissue infections. Although data on treatment of community-associated MRSA–related skin and soft tissue infections are sparse, one study demonstrated that