LAUSR

Introduction/Hypothesis: In 2016, our trauma/surgical intensive care unit (SICU) implemented a hospital-associated pneumonia (HAP) protocol that utilized a nucleic acid amplification test (NAAT) to rapidly deescalate antibiotic therapy for MRSA and MSSA. This resulted in a reduction of anti-MRSA prescribing. However, in some instances there was discordance between NAAT and respiratory cultures, where NAAT positive cases had negative culture results. This clinical scenario was not addressed in our treatment protocol, and subsequent treatment was perceived to be variable. Our objective is to describe clinical outcomes in patients with discordance between NAAT and respiratory cultures. Methods: A post-hoc analysis of a single-center quasi-experimental study was conducted for adult patients admitted to the SICU with suspected HAP from December 2016 – March 2019. Patients included had a positive respiratory MRSA or MSSA NAAT and a simultaneously obtained respiratory culture and were stratified into two cohorts: concordance and discordance between respiratory samples. The primary outcome was the rate of recurrent pneumonia, defined as a respiratory culture growing >100k cfu/ml of MSSA or MRSA within 14 days of initial culture necessitating antibiotic treatment, between groups. Results: A total of 26 patients were included, with 19 in the concordant group and 7 in the discordant group. Patients had a mean age of 45.7 vs 61.1 years, respectively and were primarily male (68.4% vs 57.1%). A full course of appropriate antibiotic therapy was completed in 94.7% of patients in the concordant group and 71.4% in the discordant group, with a mean duration of 7.6 vs 6.6 days of therapy, respectively. There were 14 repeat respiratory cultures obtained (7 in each group) within 14 days of initial culture. The rate of recurrent pneumonia was 15.8% (3/19) and 57.1% (4/7) (p=0.057), respectively. The mean ICU length of stay was 14.1 days in the concordant group vs 17.0 days in the discordant group. Conclusions: The rate of recurrent HAP in patients with discordance between NAAT and respiratory cultures was higher than the concordant group, but failed to reach statistical significance. Changes to the HAP protocol are currently under consideration.