2026 Southeastern Residency Conference

Title: Evaluation of Antibiotic Duration Between Concordant vs Discordant Multiplex Pneumonia PCR and Respiratory Culture Results 
Authors: Kala Eliacin, Rachel Tendler, Haodi Ruan  
Background/Purpose: Multiplex pneumonia PCR panels provide rapid identification of respiratory pathogens; however, discrepancies between PCR results and conventional respiratory cultures can introduce uncertainty in antimicrobial decision-making. The purpose of this study is to evaluate PCR-culture concordance vs discordance and their implications  on antibiotic duration in critically ill patients with suspected pneumonia.
Methodology: This was a single-center, retrospective chart review of adult patients admitted to the intensive care units at Emory Saint Joseph’s Hospital between January 1, 2023 and December 31, 2025 . Patients were included if they had suspected pneumonia and underwent both a multiplex pneumonia pathogen panel (PPP) and respiratory culture during the same hospitalization. Patients were excluded if they had a concurrent infection, died within 5 days of specimen collection, or had concordant negative PCR and culture results. The primary outcome was total duration of antibiotic therapy within 14 days of PPP and culture collection. Secondary outcomes included antibiotic regimens eligible for change, antibiotic regimens changed, ICU length of stay (LOS), hospital LOS, and pathogen identification. Continuous variables were reported using descriptive statistics and compared between groups using an unpaired t-test.
Results: A total of 70 patients were included, with 36 (51.4%) concordant results and 34 (48.6%) discordant results. Average age was around 62.3 years in the concordant group and 61.3 years in the discordant group and average weight was about 75 kg in both groups. Overall, the majority type of pneumonia identified in patients for both groups was community acquired pneumonia (CAP) with 41.7% in the concordant group and 47.1% in the discordant group. The mean total days of antimicrobial therapy within 14 days of index testing were 7.8 days in the concordant group compared with 8.0 days in the discordant group (p = 0.8303). ICU LOS was 13.8 days in the concordant group versus 13.2 days in the discordant group. Hospital LOS for the concordant and discordant group was 26.4 days versus 18.5 days, respectively. Antibiotic regimens were eligible for modification in 48 patients (68.6%), including 23 (63.9%) in the concordant group and 25 (73.5%) in the discordant group. Antibiotic regimens were changed in 37 patients (52.9%) overall following PPP results. Multiplex PCR detected more pathogens than respiratory culture, with common organisms including Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Overall, resistance genes were detected in 9.7% of cases with mecA/C being the most common in both the concordant group (13.5%) and discordant group (25.7%).
Conclusions: There was no difference in antibiotic duration of treatment or ICU LOS between concordant and discordant PPP and respiratory culture results. Hospital LOS, however, was shorter in the discordant group but may have been due to confounding factors. PPP results frequently identified opportunities for antimicrobial optimization, and antibiotic regimens were modified in over half of patients. These findings show that concordance vs discordance between multiplex PCR and culture results were not associated with a difference in antibiotic duration in critically ill patients with suspected pneumonia.