209. Validation of a New Risk Stratification System-Based Management for Methicillin-Resistant Staphylococcus aureus Bacteremia: Analysis of a Multicenter Prospective Study

BACKGROUND: Distinguishing between complicated and uncomplicated Staphylococcus aureus bacteremia (SAB) is therapeutically essential. However, this distinction has limitations in reflecting the various manifestation of SAB. In the light of this, Koujizer et al. proposed a new risk stratification system for metastatic infection in SAB, which involves a stepwise approach to diagnosis and treatment. We tested this risk stratification system in methicillin-resistant SAB (MRSAB) patients. METHODS: We retrospectively analyzed data of a 3-year multicenter, prospective cohort of hospitalized patients with MRSAB. We classified the patients into three risk groups: low, indeterminate, and high, based on the new system and compared between-group management and outcomes, as well as microbiologic features. RESULTS: The demographic and baseline characteristics of patients are shown in Table 1. The most frequent source of MRSAB was central venous catheter-related infection (25.5%), followed by unknown origin (15.3%) and pneumonia (11.1%). Echocardiography was performed in 248 cases (65.3%). Of 380 patients with MRSAB, 6.3% were classified as low-, 7.6% as indeterminate-, and 86.1% as high-risk for metastatic infection (Figure 1). No metastatic infection occurred in the low-, 6.9% in the indeterminate-, and 17.7% in the high-risk groups (P=0.03) (Figure 2A). After an in-depth diagnostic work-up, patients were finally diagnosed as ‘without metastatic infection (6.3%)’, ‘with metastatic infection (15.8%)’, and ‘uncertain metastatic infection (77.9%)’. 30-day mortality increased markedly as the severity of diagnosis shifted from ‘without metastatic infection’ to ‘uncertain’ and ‘with metastatic infection’ (P=0.07) (Figure 2B). In multivariable analysis, independent factors associated with metastatic complications were suspicion of endocarditis in transthoracic echocardiography, clinical signs of metastatic infection, Pitt bacteremia score ≥4, and persistent bacteremia. [Figure: see text] Figure 1. [Figure: see text] Flowchart of risk stratification and final diagnosis Figure 2. [Figure: see text] Outcomes of metastatic infection and 30-day mortality. A, metastatic infection according to the risk stratification, B, 30-day mortality according to the final diagnosis CONCLUSION: The new risk stratification system provides good discrimination in predicting metastatic complications, making it a reliable tool for guiding work-up and management of MRSAB. However, minimizing the number of ‘uncertain metastatic infection’ cases remains an area for improvement. DISCLOSURES: All Authors: No reported disclosures