571. Determining the Utility of Methicillin-Resistant Staphylococcus aureus Nares Screening in Antimicrobial Stewardship

BACKGROUND: Treatment of suspected Methicillin-resistant Staphylococcus aureus (MRSA) is a cornerstone of many antibiotic regimens; however, some anti-MRSA antibiotics are associated with toxicity. The Veterans Affairs (VA) screens each patient on admission for MRSA nares colonization. The objective of this study was to determine whether MRSA nares screening can be used as a stewardship tool for de-escalation as well as avoidance of anti-MRSA therapy. METHODS: This was a retrospective cohort study across VA medical centers nationwide from January 1, 2007 to January 1, 2018. Data from patients with MRSA nares screening were obtained from the Corporate Data Warehouse. Subsequent clinical cultures within 7 days of the nares swab were evaluated for the presence of MRSA. Sensitivity, specificity, positive predictive values (PPVs), and negative predictive values (NPVs) were calculated for the entire cohort, as well as subgroups for specific culture sites. Cultures were considered to be from a sterile site if they were from a fluid/aspirate, bone, tissue, or blood taken from the periphery. NPVs and PPVs were calculated for each of these sterile sites. RESULTS: A total of 447,579 clinical cultures were included in the final analysis. The NPV of MRSA nares screening for ruling out MRSA was 95.7% for all cultures submitted. The sensitivity and specificity for positive clinical cultures were 67.4% and 83%, respectively. The NPV for bloodstream infections (n = 64,128) was 96.2% for intra-abdominal cultures (n = 8,071) was 97.9%, for respiratory cultures (n = 75,242) was 95.3%, for wound cultures (n = 95,832) was 90.4%, and for renal cultures (n = 164,330) was 99.1%. NPVs for sterile sites are as follows: intra-abdominal (n = 7,426) was 98.1%, respiratory (n = 15,583) was 95.2%, wound (n = 51,793) was 91%. CONCLUSION: MRSA nares screening has a high NPV and specificity for ruling out potential MRSA infections at a variety of culture sites including bloodstream, intra-abdominal, respiratory, renal, and wounds. MRSA nares screening is a powerful stewardship tool for de-escalation and avoidance of empirical anti-MRSA therapy. [Image: see text] DISCLOSURES: All authors: No reported disclosures.