Clinical Inquiries

When should you suspect community-acquired MRSA? How should you treat it?

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References

EVIDENCE-BASED ANSWER

There are no clinical or epidemiologic features that will help you to clearly distinguish community-acquired methicillin-resistant Staphylococcus aureus infections (CA-MRSA) from methicillin-sensitive (CA-MSSA) infections (strength of recommendation [SOR]: B, prospective cohort studies).

Incision and drainage is the primary therapy for purulent skin and soft tissue infections (SOR: B, randomized, controlled clinical trials [RCTs]). There are inadequate data evaluating the role of oral antibiotics for MRSA (SOR: B, single RCT).

Evidence summary

Two prospective cohort studies have looked at the usefulness of clinical characteristics to help differentiate MRSA from MSSA infections. The studies—a 2002 observational study of 144 children and a 2007 study of 180 consecutively enrolled adults—found no clear distinguishing features for MRSA.1,2 They did note some commonly associated risk factors, however (TABLE).2,3

Abscess formation was the most common presentation of CA-MRSA, followed by purulent cellulitis.3,4 The prevalence and incidence of nonpurulent CA-MRSA is not well defined.

TABLE
Is it MRSA? A look at the odds

RISK FACTOROR (95% CI)*
Antibiotics in past month2.4 (1.4-4.1)
Abscess1.8 (1.0-3.1)
Reported spider bite2.8 (1.5-5.3)
Underlying illness0.3 (0.2-0.6)
History of MRSA infection3.3 (1.2-10.1)
Close contact with a person with a similar infection3.4 (1.5-8.1)
Older age (odds ratio per decade of life)0.9 (0.9-1)
Snorting or smoking illegal drugs2.9 (1.2-6.8)
Incarceration within previous 12 months2.8 (1.1-7.3)
Presentation with a nonskin infection0.3 (0.1-0.8)
CI, confidence interval; MRSA, methicillin-resistant Staphylococcus aureus; OR, odds ratio.
*Odds ratio of MRSA vs methicillin-sensitive Staphylococcus aureus or another bacterium.
Source: Miller LG, et al2 and Moran GJ, et al.3

Best treatment bet: Incision and drainage

Incision and drainage remains the mainstay of abscess treatment.3,5 A 2007 RCT of 166 indigent, inner-city patients with confirmed MRSA investigated combining incision and drainage with 7 days of therapy using either cephalexin or placebo. The primary outcome was clinical cure or failure 7 days after incision and drainage. The trial found no advantage to adding antibiotics; MRSA would likely be resistant to cephalexin in any case.6

A 2006 summary from Clinical Evidence found no RCT support for any outpatient antibiotic.7 No evidence exists that intranasal mupirocin or antiseptic body washes reduce the recurrence rate.7 We found no studies evaluating the optimal treatment of purulent skin and soft tissue infections without abscesses.

Evidence-based answers from the Family Physicians Inquiries Network

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