Early Use of Molecular Diagnostics in the Emergency Department Reduces All-Cause Mortality in Patients with Pneumonia at Risk of Multidrug-Resistant Pathogens

Background/Objectives: Patients with community-acquired pneumonia at risk of multidrug-resistant pathogens (CAP-MDR) represent a high-risk population in which empiric therapy is frequently inadequate. Evidence on the impact of multiplex syndromic panels (MSP) on clinical outcomes in CAP-MDR pneumonia remains limited, particularly in the emergency department (ED). Methods: We conducted a single-center observational pre–post study including patients presenting to the ED with CAP-MDR. Patients were managed either with early MSP-guided therapy (prospective cohort) or standard empiric treatment (retrospective cohort). The primary outcome was 30-day mortality. Analyses were performed in the overall population and subsequently in a propensity score–matched cohort. Results: A total of 718 patients were included (MSP n = 128; no-MSP n = 590). Thirty-day mortality was significantly lower in the MSP group (22.7% vs. 31.9%; p = 0.04). At multivariable logistic regression, MSP use was independently associated with reduced mortality (OR 0.51, 95% CI 0.30–0.88; p = 0.016), confirmed by Cox analysis (HR 0.60, 95% CI 0.36–0.99; p = 0.04). Kaplan–Meier analysis showed improved survival (log-rank p = 0.002). After propensity score-matching (MSP n = 128; no-MSP n = 128), mortality remained lower in the MSP group (22.7% vs. 35.1%; p = 0.02). MSP use was independently associated with reduced mortality (OR 0.45, 95% CI 0.20–0.99; p = 0.04), confirmed by Cox regression (HR 0.50, 95% CI 0.31–0.82; p = 0.006). Conclusions: Early use of MSP in patients with CAP-MDR was associated with a significant reduction in 30-day mortality. Rapid molecular diagnostics may provide the greatest clinical benefit when applied early in high-risk populations in which empiric therapy is frequently inadequate.