New Zealand has the highest rate of Legionnaires’ disease (pneumonia caused by Legionella bacteria) in the world. As a notifiable disease and the most common cause of pneumonia during peak season, Legionella requires specific antibiotic treatment. However, clinicians must wait 24–48 hours for testing results, and current guidelines for treating suspected pneumonia chose antibiotic treatment based on severity rather than likely cause. As a result, many patients with Legionnaires’ disease do not receive specific anti-Legionella treatment as early as needed. Delays in the diagnosis of Legionnaires disease put patients at greater risk of treatment failure, with likely consequences including increased repeat hospitalisations, longer length of hospital stay and longer recovery times. We aim to develop and test a novel approach to selecting antibiotics for community-acquired pneumonia that will provide early treatment for Legionnaires’ disease that is more targeted and accurate than current approaches.