Background: Both national and regional guidelines are regularly published in order to ensure correct diagnosing and treatment of pneumonia contemporary with limiting unnecessary use of antibiotics. Recent studies have shown microbiological findings that question the recommendations in the Danish guidelines. This study aimed to report the aetiology, antibiotic treatment and guideline-adherence in the empirical management of patients hospitalised with pneumonia.

Methods: In this retrospective descriptive study, all adults hospitalised with pneumonia at the Emergency Department of Aalborg University Hospital, Denmark, in the period between November 2021 and June 2022 were included. Patients who were primarily admitted because of COVID-19 were excluded. Hospital records were reviewed, and the microbiological data and the antibiotic therapy were analysed.

Results: The study included 306 patients with a median age of 77 years. In total, 42% of the patients had chronic obstructive pulmonary disease (COPD), 16% had been hospitalised within the last 28 days and 8% were immunocompromised. The majority had a CURB-65 score below 2 (73%). In total, 97% had minimum one microbiological testing of which the proportion of positive findings was 26%. The most frequently identified pathogen was influenza A (22%). The dominant bacterial pathogen was Haemophilus influenzae (16%) followed by Staphylococcus aureus (10%). H. influenzae was the dominant bacterial pathogen amongst both COPD patients and non-COPD patients. S. aureus was the most frequently detected pathogen in patients with a CURB-65 score of 3-5 (23%). Regarding the antibiotic treatment, 40% of the immunocompetent patients with community-acquired pneumonia (CAP) did not receive correct empirical treatment in adherence to the regional guidelines. The major reason for non-adherence to guidelines was overtreatment with broad-spectrum antibiotics. At admission time, the most frequently prescribed empirical antibiotics were amoxicillin/clavulanic acid (32%), piperacillin/tazobactam monotherapy (21%) and penicillin monotherapy (18%), respectively. The median length of the antibiotic treatment was 8 days.

Conclusion: Our study showed that H. influenzae was the dominant bacterial finding amongst both COPD and non-COPD patients with pneumonia. Amoxicillin/clavulanic acid was the most frequently prescribed antibiotic at admission time. In total, 40% of the immunocompetent patients with CAP did not receive empirical antibiotic treatment in adherence to the regional guidelines. The main reason for non-adherence to guidelines was overtreatment with broad-spectrum antibiotics.