News & Updates

Dr. Paul Kamitsuka published in the New England Journal of Medicine

September 04, 2008

Incision and Drainage plus Anti-MRSA Therapy

First, although decisions regarding the choice of empirical antibiotics should be made on the basis of local resistance data when possible, the likelihood that our patient has a community-associated MRSA infection is considerable. He is an athlete with exposure to skin flora through physical contact in geographic locales across the United States. In a study of acute skin and soft-tissue infections in patients presenting to emergency departments in 11 U.S. cities, 59% of the infections were due to community-associated MRSA (range, 15 to 74).6 Nonetheless, it is advisable to obtain a sample for culture at the time of incision and drainage, not only to focus current treatment but also to have susceptibility data in case the infection recurs and eradication of community-associated MRSA is needed.

Second, although it has long been accepted that most MRSA soft-tissue abscesses may be treated with incision and drainage alone,13 recent data suggest that antibiotics may play a more important role in treating abscesses due to community- associated MRSA. Unlike traditional MRSA strains,20 community-associated MRSA strains often produce Panton-Valentine leukocidin, a pore-forming cytotoxin associated with increased tissue destruction. In a retrospective cohort study of 492 adults with 531 independent episodes of skin and soft-tissue infections with community associated MRSA, most of whom underwent incision and drainage, therapy was successful in 95% of those receiving an active antibiotic as compared with 87% of those who did not.10 Use of an inactive antimicrobial agent was an independent predictor of treatment failure on logistic regression analysis (adjusted odds ratio, 2.80; 95% confidence interval, 1.26 to 6.22; P = 0.01). Szumowski et al.21 found, in a retrospective review of 399 sequential cases of culture-confirmed S. aureus skin and soft-tissue infections, including 227 cases of MRSA infection, use of an antibiotic to which the isolate was sensitive was associated with an increased likelihood of clinical resolution (odds ratio, 5.91, as compared with no such use), after adjustment for incision and drainage and human immunodeficiency virus status. Finally, in a prospective observational study of a pediatric population, Lee et al.8 found that an infected site more than 5 cm in diameter treated by means of incision and drainage was less likely to respond in the absence of effective antibiotic therapy than with such therapy. Our patient's abscess is 5 cm in diameter.

A third consideration is whether providing effective antibiotics will decrease the risk of persistent carriage and thereby prevent recurrent infection as well as spread of community-associated MRSA to others. The answer to this question awaits further study, although in the absence of hard data clinicians often find themselves attempting to break the cycle of recurrent infection with the combined use of systemic antibiotics and topical antiseptics. Recurrent skin and soft-tissue infection is a vexing characteristic of community-associated MRSA, with estimates of recurrence ranging from 10%22 to 23.8%.21 Although some of these recurrences may be due to infection with a different community-associated MRSA strain, others result from persistent cutaneous carriage of the original strain after resolution of the initial infection. The spread of community-associated MRSA to household contacts is also problematic. Zafar et al.23 found that 20% of household contacts of patients with community- associated MRSA skin and soft-tissue infections carried MRSA, with half the MRSA strains related to the patient's infective isolate. A previous study reported household MRSA-carriage rates of 14.5%.24 Anecdotal evidence suggests that more than 60% of households of children hospitalized with community-associated MRSA infections include one or more family members who had a putative MRSA infection in the previous 6 months.22 The likelihood of clinical infection after colonization by community-associated MRSA appears to be considerable. Ellis et al.,25 in a prospective observational study of soldiers, found that soft tissue infections developed over a period of 8 to 10 weeks in 9 of 24 (38%) of those with community-associated MRSA in their nares, as compared with only 8 of 229 (3%) of those with nasal carriage of MSSA (P<0.001).

For our athlete, eager to resolve his infection before next week's game, the provision of an antibiotic effective against community-associated MRSA, perhaps with the use of 2% chlorhexidine for bathing, appears to be prudent.

No potential conflict of interest relevant to this article was reported.

From Wilmington Health and the Department of Medicine, University of North Carolina School of Medicine, Wilmington.

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Copyright 2008 Massachusetts Medical Society.

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