Microbiological findings and antibiotic treatment in community-acquired pneumonia: a retrospective cohort study

BACKGROUND: National and regional guidelines are regularly updated to ensure the correct diagnosis and treatment of pneumonia while minimizing unnecessary antibiotic use. However, recent microbiological studies have raised concerns about the recommendations in Danish guidelines. This study aimed to describe the aetiology, empirical antibiotic treatment, and adherence to guidelines in the management of hospitalised patients with community-acquired pneumonia (CAP). METHODS: This retrospective cohort study included all adults hospitalised with CAP at the Emergency Department of Aalborg University Hospital, Denmark, over a one-year period from November 2021 to October 2022. Hospital records were reviewed, and the microbiological data and the antibiotic therapy were analysed. RESULTS: A total of 366 patients were included in the study. The most frequently identified pathogen was Haemophilus influenzae (25%), followed by influenza A (22%), Staphylococcus aureus (9%), respiratory syncytial virus (9%) and Streptococcus pneumoniae (8%). H. influenzae was the dominant bacterial pathogen in both patients with COPD and without COPD. S. aureus was among the most commonly detected pathogens in patients with a CURB-65 score of 3–5 (22%). Regarding antibiotic treatment, 41% of the patients did not receive the recommended therapy. Non-adherence to the guidelines was primarily driven by the overuse of broad-spectrum antibiotics. At admission time, the most commonly prescribed empirical antibiotics were amoxicillin/clavulanic acid (33%), piperacillin/tazobactam monotherapy (23%) and penicillin monotherapy (21%), respectively. CONCLUSION: Our study found that H. influenzae was the most frequently detected bacterial pathogen identified in both patients with and without COPD hospitalised with CAP. These findings highlight the need to reconsider the empirical treatment recommendations in the Danish guidelines. Amoxicillin/clavulanic acid was the most commonly prescribed empirical antibiotic. However, a substantial proportion of patients did not receive guideline-adherent treatment. Broad-spectrum antibiotic overuse was the main issue.