460. Ceftriaxone vs. Standard of Care for Definitive Treatment of Methicillin-Susceptible Staphylococcus aureus Infections

BACKGROUND: β-Lactam antibiotics, specifically nafcillin, oxacillin, and cefazolin, have proven efficacy for methicillin-susceptible Staphylococcus aureus (MSSA) infections. Outpatient antimicrobial therapy (OPAT) with these agents is limited due to side effects and multiple doses required per day. Ceftriaxone, a third-generation cephalosporin, has a favorable profile for OPAT. Limited evidence supporting ceftriaxone therapy for MSSA infections prevents its widespread use. METHODS: A multi-center, retrospective cohort study comparing patients who received cefazolin or nafcillin to patients who received ceftriaxone for treatment of microbiologically proven MSSA infections was conducted from February 2016 to February 2018. The primary outcome of interest was a clinical success, defined as the absence of infection-related readmission, worsening infection, or recurrent infection within 90 days. Secondary outcomes included the rate of adverse reactions, length of stay, and impact of Infectious Diseases (ID) consult. RESULTS: 66 patients treated with ceftriaxone and 156 patients treated with cefazolin or nafcillin were included. Skin and soft tissue and bone and joint were the most common infections in the ceftriaxone group, whereas bacteremia was most common in the nafcillin and cefazolin group. There were significant differences in baseline age (61 years vs. 59 years; P = 0.036) and intravenous drug use (1 patient vs. 25 patients; P = 0.002) between groups. As shown in Table 1, there were significantly lower rates of clinical success with ceftriaxone compared with standard of care as a composite of all infection sites (78.8% vs. 91%; P = 0.012). No statistically significant differences were seen in safety outcomes or ID consultation. Length of stay was significantly longer in the nafcillin and cefazolin group (5.2 days vs. 12.8 days; P ≤ 0.0001). CONCLUSION: The results of this study indicate that patients treated with ceftriaxone for MSSA infections had significantly lower rates of clinical success compared with standard of care antibiotics. Nafcillin or cefazolin should remain as first-line agents for treatment of bone and joint infections and skin and soft-tissue infections due to MSSA. [Image: see text] DISCLOSURES: All authors: No reported disclosures.