Time to Vancomycin De-Escalation in Pneumonia Patients Screened for MRSA Using Culture vs PCR Testing

Background: There is no published data comparing time to vancomycin de-escalation for patients with respiratory infections screened for methicillin-resistant Staphylococcus aureus (MRSA) with nasal culture compared to polymerase chain reaction (PCR). Objective: To compare the duration of vancomycin therapy between patients who underwent MRSA testing via culture vs PCR. Methods: This was an Institutional Review Board (IRB) approved, multi-site, retrospective cohort study which included patients receiving vancomycin therapy for the treatment of pneumonia who underwent MRSA screening with either culture or PCR testing. The primary outcome was total days of vancomycin therapy. Secondary outcomes included length of stay (LOS), incidence of acute kidney injury, and time from nasal swab to vancomycin discontinuation. Results: A total of 120 patients met inclusion criteria, with 57 in the culture group and 63 in the PCR group. The median duration of vancomycin was significantly shorter in the PCR group compared to the culture group (0.77 vs 1.80 days; P < 0.001). The median time from nasal swab collection to vancomycin discontinuation was also significantly shorter in the PCR group compared to the culture group (0.29 vs 1.38 days; P < 0.001). There was no difference in the median LOS or the incidence of acute kidney injury (AKI) between groups. Conclusions: This is the first study to directly compare duration of vancomycin therapy as the primary outcome for patients who underwent MRSA screening with nasal culture vs PCR. The use of MRSA PCR testing was associated with a significantly shorter duration of vancomycin therapy in patients with pneumonia when compared to culture-based testing.