452. Antibiotic Duration, but Not Size, Impacts Clinical Cure of Limited Skin and Soft-Tissue Infection After Incision and Drainage

BACKGROUND: Incision and drainage (I&D) is the most common treatment for skin abscesses. A recent randomized clinical trial (RCT) of outpatients with limited (≤5 cm) skin abscesses demonstrated antibiotic therapy with clindamycin or trimethoprim-sulfamethoxazole (TMP-SMX) was superior to I&D alone. We performed a subgroup analysis to measure the effect of antibiotic duration and abscess size on clinical cure at 7–10 days after antibiotic completion. METHODS: Participants with complete data regarding adherence to the 10-day treatment were included. Demographic and baseline clinical features were compared using t-test, Pearson’s chi-square or Fisher’s exact test, or a non-parametric equivalent where appropriate. Largest abscess dimension (cm) was dichotomized by median size. The effect of antibiotic duration, abscess size (≤ median vs. >median) and covariates on clinical cure were measured using logistic regression. Breslow-Day Test for Homogeneity was used to assess the interaction between treatment and abscess size. RESULTS: Of 786 participants in the intention-to-treat analysis, complete adherence data were available for 680 (87%) participants. Of these, 463 (68%) received either antibiotic: 421 (91%) completed 10 days of therapy, 29 (6.3%) ≤7 days and 20 (4.3%) ≤5 days. Only antibiotic treatment duration was associated with clinical cure (table). Odds of clinical cure were 1.7 (95% CI: 1.5, 2.0) times higher for each additional day of treatment. Median abscess size was 2.5 cm (range: 0.2–5); 364 participants had abscesses ≤ median vs. 316 >median. Assessed continuously, abscess size was not associated with cure within antibiotic groups (table) or between placebo and treatment groups (OR 0.94, 95% CI: 0.58–1.5). Stratifying on size, no significant interaction was observed with antibiotic treatment (Breslow-Day P = 0.13). CONCLUSION: Adherence to the treatment protocol was high. These data suggest that longer courses of antibiotic therapy in conjunction with I&D are associated with successful treatment of limited skin abscesses. Size was not associated with clinical cure. Prospective RCTs to determine the optimal length of treatment are needed. [Image: see text] DISCLOSURES: All authors: No reported disclosures.