Guideline-concordant therapy for community-onset pneumonia considering risk factors for drug-resistant pathogens: a propensity score-matched study.

PURPOSE: Guideline-concordant therapy (GCT) has been associated with improved outcomes in patients with community-onset pneumonia. However, the impact of GCT remains unclear when the risk of drug-resistant pathogens, such as methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa, is considered. METHODS: We retrospectively evaluated the safety and efficacy of GCT for hospitalised adult patients with community-onset pneumonia at a 270-bed community hospital in Yamanashi, Japan, between January 1, 2020, and May 31, 2025. GCT was defined according to adult pneumonia guidelines issued by the Japanese Respiratory Society 2024 (JRS 2024). Patients were matched one-to-one using propensity score matching. The primary endpoint was 28-day mortality. The study was approved by the Yamanashi Red Cross Hospital Ethics Committee (approval number: 7 - 2, approval date: 01/September/2025). RESULTS: Of the 540 eligible patients, 380 were included in the matched analysis. The Kaplan-Meier curve for 28-day mortality showed no statistically significant difference between the GCT group and the non-GCT group (hazard ratio, 1.02; 95% CI, 0.82-1.27, P = 0.94). CONCLUSION: In this single-center observational cohort of patients with community-onset pneumonia, GCT according to the JRS 2024 guideline was not associated with lower 28-day mortality than non-GCT. These findings should be interpreted cautiously in light of the observational study design, the clinical heterogeneity of the cohort, and the potential for residual confounding. Further studies are needed to evaluate the effectiveness of JRS 2024-based treatment strategies in broader clinical settings.