Trimethoprim-sulfamethoxazole or clindamycin for community-associated MRSA (CA-MRSA) skin infections

Background: In the United States, community-associated methicillin- resistant Staphylococcus aureus (CA-MRSA) has emerged as the predominant cause of skin infections. Trimethoprim-sulfamethoxazole (TMP-SMX) and clindamycin are often used as first-line treatment options, but clinical data are lacking. Methods: We conducted a retrospective cohort study of outpatients with skin and soft tissue infections managed from July 1 to December 31, 2006. Patients younger than 18 years of age were excluded, as were those who had no clinical admission or progress notes; were hospitalized within the 90 days before admission; were hospitalized with polymicrobial, surgical site, catheter-related, or diabetic foot infections; or were discharged to places other than home. Patient demographics, comorbidities, diagnoses, cultures, prescribed antibiotics, susceptibilities, surgical procedures, and health outcomes were extracted from electronic medical records. Patients were divided in 2 cohorts for further analysis: TMP-SMX and clindamycin. The primary study outcome was composite failure defined as an additional positive MRSA culture from any site 5 to 90 days after treatment initiation or an additional intervention during a subsequent outpatient or inpatient visit. Baseline characteristics and failure rates were compared using χ², Fisher's exact, and Wilcoxon rank sum tests. Results: A total of 149 patients were included in this study. These patients had a median age of 36 years, 55% were men, 71% were Hispanic, 42% were uninsured, and 60% received an incision and drainage procedure. Patients who did not receive incision and drainage were twice as likely to experience the composite failure endpoint (57% vs 29%; P < .001). Failure rates were 25% for patients who received incision and drainage plus antibiotics compared with 60% for patients who received incision and drainage minus antibiotics (P = .03). When patients who did not receive incision and drainage were excluded, there were no significant differences between the TMP-SMX (n = 54) and clindamycin (n = 20) cohorts with respect to composite failures (26% vs 25%), microbiologic failures (13% vs 15%), additional inpatient interventions (6% vs 5%), or additional outpatient interventions (20% vs 20%). Conclusions: Our findings reinforce the belief that incision and drainage and antibiotics are critical for the management of CA-MRSA skin infections. Patients who receive TMP-SMX or clindamycin for their CA-MRSA skin infections experience similar rates of treatment failure.