(522) Impact of Methicillin-Resistant Staphylococcus aureus Nasal PCR on Vancomycin Use in Pneumonia

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) polymerase chain reaction (PCR) is a rapid diagnostic testing used for lower-respiratory tract infections (LRTI) that can reduce unnecessary vancomycin (VAN) utilization due to a high negative-predictive value. The MRSA PCR test may provide more timely results compared to nasal culture, which requires prolonged incubation. There are limited data that directly compare vancomycin utilization and patient safety between these two rapid diagnostic tests. The purpose of this study was to assess the impact of MRSA nasal PCR on vancomycin utilization after transitioning from MRSA culture.

Methods: This was an IRB-approved, single pre and post-test quasi-experiment conducted at a five-hospital health system. Hospitalized adult patients admitted from 9/2021-12/2021 (MRSA culture) and 9/2022-12/2022 (MRSA PCR) were included. Additional inclusion criteria were: receipt of intravenous vancomycin for suspected LRTI, antibiotic therapy ≥5 days, negative MRSA PCR or culture. Patients with ventilator-associated pneumonia and COVID-19 infection were excluded. The primary endpoint was the proportion of patients with VAN levels ordered. Secondary endpoints were VAN duration (days), the incidence of VAN-associated acute kidney injury (AKI), and all-cause 30-day readmission.

Results: 200 patients were included; 100 culture and 100 PCR groups. Forty percent of patients received care in the intensive care unit. The proportion of patients that had a VAN level ordered was 67% culture vs. 52% PCR (P=0.031). The median (IQR) number of VAN levels ordered was 1(0-2) and 1(0-1) (P=0.029) in culture vs. PCR respectively. The median (IQR) VAN duration was 3 (2-4) and 2 (1-3) days culture vs. PCR (P < 0.001). The incidence of VAN-associated AKI was 19% vs. 4% in culture vs. PCR (P < 0.001). There was no difference in readmission rates in culture (28%) vs. PCR (30%) (P=0.755). When adjusting for critical illness and sex, patients in the PCR group were significantly less likely to develop AKI adjusted odds ratio (0.14; 95%CI, 0.04-0.44).

Conclusions: Patients in the MRSA PCR group had significant reductions in vancomycin utilization and AKI without any change in readmissions. These findings support the adaptation of more efficient rapid diagnostic tests in infected patients.