Swab Testing to Optimize Pneumonia Treatment With Empiric Vancomycin

Methicillin-resistant Staphylococcus aureus (MRSA) is a critical antimicrobial resistant threat responsible for greater than 300,000 inpatient infections and 15,000 deaths per year in the United States. Community-acquired pneumonia (CAP) is a major driver of hospital antibiotic use. Nationally, there are around 600,000 CAP-related hospital admissions annually. However, MRSA is an infrequent cause of community-acquired pneumonia (CAP), accounting for less than 1% of cases. Despite this, MRSA is a frequently feared cause of CAP, which leads to the frequent use of vancomycin, an anti-MRSA antibiotic, in empiric CAP treatment. Inappropriate antibiotic use can lead to avoidable adverse drug events and costs, as well as drive antimicrobial resistance. Empiric vancomycin use in patients hospitalized for pneumonia has demonstrated increased mortality, acute kidney injury (AKI), and secondary infections. The use of vancomycin is unfortunately associated with a high risk for toxicity and serious adverse events. Up to two-thirds of patients receiving high dose vancomycin develop AKI. Additionally, bone marrow suppression, linear IgA bullous dermatosis, anaphylaxis, and life-threatening hypersensitivity reactions are seen with vancomycin use. Furthermore, vancomycin is a costly antibiotic to use in the hospital as it requires careful monitoring due to its narrow therapeutic range and high risk of toxicity. There is growing data to support the use of MRSA nasal swabs as a screening method to guide de-escalation of vancomycin use in CAP. A 2018 meta-analysis found using nasal swabs for MRSA screening had an overall 96.5% negative predictive value (NPV) for pneumonia, which was increased to 98.1% among patients with CAP or Healthcare-associated pneumonia (HCAP). Multiple retrospective studies along with one prospective study utilizing MRSA nasal swab-based de-escalation protocols have shown MRSA nasal swab use to be effective in decreasing vancomycin use and associated costs without having any negative effects on patient outcomes. Among these studies, significant decreases in hospital length of stay and rate of AKI have been shown. Furthermore, the use of MRSA detection in nasal swabs is now consistent with guideline-based management of CAP. However, all the aforementioned studies are quasi-experimental analyses. To date there are no randomized controlled studies of the use of MRSA nasal swab guided antibiotic de-escalation.