(526) Evaluation of Short Versus Long Antibiotic Courses in Non-Deep-Seated Actinomycosis Infection

Introduction: Actinomyces spp. are normal flora that can cause infection requiring source control and extensive antibiotic therapy. Data are limited regarding optimal treatment. This study evaluated actinomycosis recurrence rates in patients treated with short and long antibiotic courses.

Methods: This single-center, retrospective cohort study included adult patients diagnosed with actinomycosis treated with antibiotics. Patients were grouped into short ( < 90 days) or long (≥90 days) treatment courses. The primary outcome was infection recurrence within 12 months. Secondary outcomes were hospital length of stay (LOS) and mortality (hospital and 12-month). Subgroup analyses included ICU admission impact on treatment duration and cephalosporin therapy influence on outcomes. A multivariate logistic regression was used to determine risk factors for long antibiotic courses.

Results: The study included 100 (78 short; 22 long) patients. A total of 33 (33%) patients were admitted to an ICU at the time of diagnosis (short, 25 [32.5%] vs long, 8 [36.4%]; P=0.70). No difference was observed in infection recurrence (short, 1 [1.4%] vs long, 1 [4.5%]; P=0.41). Hospital LOS (short, 9 [4.8-14.0] vs long, 14 [7.5-17.3]; P=0.071) and in-hospital (short, 6 [7.7%] vs long, 1 [4.5%]; P>0.99) and 12-month (short, 4 [5.5%] vs long, 2 [9.1%]; P=0.62) mortality were similar. Median treatment duration was similar between ICU and non-ICU patients (16 [6.5-94.5] vs 21 [10.0-70.0] days; P=0.43), but IV therapy was longer in the ICU (7 [5.0-17.5] vs 3 [0-12.0]; P=0.028). No patients with cephalosporin monotherapy (N=22) had infection recurrence. Hospital (cephalosporin, 1 [6.3%] vs alternative, 6 [7.1%]; P=>0.99) and 12-month (cephalosporin, 1 [6.3%] vs alternative, 5 [6.3%]; P=>0.99) mortality was no different when cephalosporin was used. Infectious disease consult increased the risk for long treatment (OR 6.84, 95% CI 1.79-26.10; P=0.005).

Conclusions: Actinomycosis infection recurrence was similar between treatment courses < 90 days and ≥90 days. Hospital and 12-month mortality were similar between groups and ICU admission status did not influence treatment duration. Larger, adequately powered studies are needed to refine optimal duration versus stewardship opportunities.