Background and importance Community-acquired pneumonia (CAP) is still one of the leading causes of death worldwide. In previous studies, guideline adherence to national and international CAP guidelines in terms of agent choice was found to be poor. Implementation of the Antibiotic Stewardship Program (ASP) aimed to improve correct and responsible antibiotic use by encouraging guideline adherence.

Aims and objectives This retrospective observational before-and-after study aimed to evaluate whether the ASP may improve guideline adherence, antibiotic exposure, and clinical outcomes in patients hospitalised with CAP in Hungary.

Materials and methods The study was conducted at the Pulmonology Department of a tertiary care medical centre in Hungary. The ASP implementation consisted of written and published guidelines available to all professionals, continuous supervision, and counselling services on antibiotic therapies. The intervention was performed by a multidisciplinary antibiotic stewardship team (AST) at an individual level, with the aim of ensuring compliance with CAP guidelines. Overall guideline adherence (agent selection, route of administration, dose), clinical outcomes (length of stay (LOS), 30-day mortality), and antibiotic exposure were compared between pre-intervention and ASP periods (both retrospective observational). Fisher’s exact test and t-test were applied to compare categorical and continuous variables, respectively. Significant p values were defined as below 0.05.

Results A significant improvement in overall CAP guideline adherence by 30.2%, p = 0.017 and a significant reduction in the total duration of antibiotic therapy by 13.5%, p = 0.002 were observed. Guideline non-adherent combination therapies of metronidazole decreased significantly by 28.1%, p ˂0.001. Antibiotic exposure decreased by 7.2%, p = 0.061, and sequential therapy increased significantly by 10.5%, p = 0.01. Moreover, ASP has a positive effect on clinical outcomes (LOS decreased by 13.5%, p = 0.016; 30-day survival increased by 5.9%, p = 0.711).

Conclusion and relevance The availability of written protocols on the ward and the continuous counselling service are crucial in optimising antibiotic use. Implementation of ASP led to a significant improvement in CAP guideline adherence and sequential therapy, which also entailed a significant reduction in the total duration of antibiotic therapy and length of stay.