79 - Outcomes Associated with the Utilization of the Methicillin-Resistant Staphylococcus aureus (MRSA) Nasal Polymerase Chain Reaction (PCR) Assay to De-escalate Vancomycin Therapy in Patients with Suspected Pneumonia at a Rural Community Hospital

Background: Vancomycin is often added to standard inpatient community acquired pneumonia therapy, but the incidence of MRSA pneumonia is relatively low. The MRSA nasal PCR assay is used to detect if a patient’s nares are colonized with MRSA. Studies have found that this test has an excellent negative predictive value at ruling out MRSA pneumonia. In practice, there is reluctance to utilize this data to de-escalate vancomycin, possibly because little data exists investigating clinical outcomes associated with this intervention. The purpose of this study was to evaluate how this assay, in combination with antimicrobial stewardship, impacts de-escalation of vancomycin and consequently, length of stay, days of therapy, readmission, and mortality.

Methods: We performed a cohort study of patients who received vancomycin for pneumonia during the period 2017-2019. In July 2018, we implemented a pharmacy-led process to de-escalate vancomycin in pneumonia patients based on the results of the nasal MRSA PCR. Patient were excluded if they had concomitant skin/skin structure infection, osteomyelitis, were transferred to another facility, signed out against medical advice, or required mechanical ventilation. Data on patient characteristics, disease severity, length of stay, days of therapy, readmission, and mortality were compared between the groups.Figure 1: Patient disposition with reasons for exclusion from study


Results: 101 and 107 patients were included in the before and after group, respectively. The average length of stay was 5.31 (before group) vs 4.33 days (after group), resulting in a 0.98 day decrease (p=0.0095). Days of therapy was 3.16 (before group) vs 1.96 days (after group), resulting in a 1.2 day reduction (p< 0.0001). 30-day mortality was significantly higher in the before group (19.8%) than the after group (9.3%) (RR 0.47, 95% CI 0.23-0.96). 30-day readmission was similar between the two groups (21.8% pre-intervention vs 19.6% post-intervention, p=0.7).Figure 2: Length of Stay and Duration of therapy reductions between the pre- and post-intervention groups.
Figure 3: 30-day readmission rate and 30-day mortality rate in the pre- and post-intervention groups.
Figure 4: Vancomycin days of therapy per 1000 patient days from July 2017 to May 2020


Conclusion: Use of the MRSA nasal PCR to deescalate vancomycin therapy appears to significantly reduce length of stay and days of vancomycin therapy. Use of this assay did not negatively impact readmission but, may have a positive impact on mortality. Further research is needed to determine the impact of this intervention on length of stay and mortality.