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.

Inclusion criteria

• Adult (age greater than or equal to 18) patients admitted/transferred to the Vanderbilt University Medical Center (VUMC) Medical Intensive Care Unit (MICU) from the VUMC Emergency Department or from a hospital floor within 48 hours of admission.
• Suspicion for pneumonia on admission (defined as an indication for antibiotics of "respiratory infection" and/or an order for a respiratory culture i.e., sputum culture, tracheal aspirate culture, or bronchoalveolar lavage (BAL) culture).
• No topical nasal decolonization during hospitalization prior to collection of MRSA nasal swab PCR.
• Must match both of the following in either order:

• The patient has been admitted to and physically located in the MICU.
• The patient has received a continuing vancomycin order, or a pharmacokinetics consult for a continuing vancomycin order, no later than 24 hours following their physical admission to the MICU.

Exclusion criteria

• Hospital stay of longer than 48 hours prior to MICU admission.
• Known to be a prisoner