Methods

Implementation occurred at a 3-hospital, nonteaching, community healthcare system in Western Pennsylvania that encompasses a total of 585 licensed beds with an average case mix index of 1.71. The system utilized a TASP via a hub-and-spoke model with central ID experts advising local non-ID clinical pharmacists assigned to dedicated stewardship coverage. The TASP utilized prior authorization for select antimicrobials and daily prospective audit with intervention and feedback via synchronous ASP calls between the local pharmacists and central ID team (calls occurred Monday through Friday). All interventions were made and tracked by the local stewardship pharmacists. Baseline antimicrobial use data suggested elevated use of vancomycin with pneumonia listed as a frequent indication. Existing MRSA nares testing relied on chromogenic agar (CA) culture-based assay, and no stewardship protocol existed to guide and oversee MRSA nares testing or vancomycin discontinuation based on testing results.

A pharmacy protocol was authored by the central tele-ID team alongside local pharmacy, medical, and microbiology leadership. The protocol was approved by hospital leadership as an Instituitional Review Board-exempt quality improvement project and went live on April 1, 2021. The intervention period was divided into two phases where the protocol first utilized the existing CA culture-based (CHROMagar™ MRSA) MRSA nares assay (phase I: 4/2021–9/2021) followed by the transition to a PCR-based assay (Cepheid GeneXpert®) (phase II: 4/2022–9/2022) to assess the incremental impact of rapid molecular testing on TASP protocol effectiveness. Intervention periods (phases I and II) were compared with a preintervention period (4/2019–9/2019) where the CA-based MRSA nares assay was available for providers to order without antimicrobial stewardship oversight.

Pharmacists reviewed all patients admitted to one of the three system hospitals who had vancomycin ordered with the indication of either community-acquired pneumonia (CAP) or hospital-acquired pneumonia/ventilator-associated pneumonia (HAP/VAP) (Figure 1). MRSA nares testing was ordered by the local pharmacists per protocol. The pharmacist communicated with the primary nurse to ensure correct specimen collection. The microbiology laboratory batched MRSA CA cultures once daily in the morning which resulted after 24 hours. Upon transition to the PCR-based assay, samples were run as received during regular daytime hours with a test turnaround time of 1 hour. Assay results were available in the electronic health record (EHR) with a stewardship nudge addressing the negative predictive value of a negative test result in pneumonia. Pharmacists screened assay results using either the EHR or antimicrobial stewardship software (TheraDoc®, Charlotte, NC) once daily. Negative test results were verbally communicated to the primary medical team. Antimicrobial stewardship guidance to discontinue empiric vancomycin was provided when no other appropriate indication for vancomycin therapy was present as per protocol criteria (Supplemental Figure 1). All local pharmacists and primary providers received initial in-person and newsletter education on the evidence basis for MRSA nares testing, testing indication, protocol workflow, and exclusion criteria from nares-based vancomycin de-escalation.

Figure 1.

Pharmacist MRSA nares protocol workflow. Note: MRSA, methicillin-resistant Staphylococcus aureus.

Interventions were tracked in an antimicrobial stewardship intervention tracker, and manual data extraction was performed from the EHR. Outcome measures included the rate of MRSA swabs ordered, efficiency metrics (time to swab order, collection, and result), duration of vancomycin therapy among patients with negative MRSA screen results, rate of same-day vancomycin discontinuation, rate of  acute kidney injury (AKI) (serum creatinine elevation of ≥ 0.3mg/dl from baseline per Kidney Disease Improving Global Outcomes guidelines), and rate of nares to respiratory culture discordance. ^{Reference Khwaja9} MRSA nares test characteristics were evaluated against respiratory cultures collected within 7 days of screening.

Data were summarized using descriptive statistics including means, frequencies, and percentages. Bivariate analyses were conducted using χ² or Fisher’s Exact for categorical variables and the Mann-Whitney test for non-normally distributed continuous variables. All statistical analyses were performed in SAS statistical software, version 9.4 (SAS Institute, Cary, North Carolina).