Community acquired pneumonia (CAP) is increasing in incidence, and is presently responsible for about 1% of emergency medical admissions with an associated mortality of between 5% and 24%. Improving the outcome of CAP is, therefore, a major health priority, but what is the best method to do this? Many audits have shown poor adherence to national guidelines for the management of CAP, with the inference that this may negatively affect outcome. One example of poor compliance is with empirical antibiotic therapy, the mainstay of treatment for most patients. Major guidelines for CAP advise that patients admitted to hospital with moderate and severe CAP should be treated with a combination of a β lactam and a macrolide,1 yet large national audit datasets show that over a third of patients may be treated with β lactams alone.2 ,3 If the poor compliance with CAP guidelines affects outcome this would have serious implications for care of these patients and provide an obvious mechanism to improve their mortality. Conversely, using dual therapy when monotherapy is adequate will incur unnecessary additional cost, an increased risk of complications, and potentially encourage antibiotic resistance among commensal organisms.

The guidance to use dual β lactam and macrolide antibiotics for empirical therapy of CAP for hospitalised patients moderate and severe CAP is based on microbiology data showing around 20% of CAP is caused by ‘atypical’ organisms (Mycoplasma pneumoniae, Chlamydophila pneumoniae and Legionella pneumophila); these do not respond to β lactams but are sensitive to macrolides. However, there are almost no controlled trial data on the relative efficacy of these regimens to support the guideline recommendations. In this context, Rodrigo et al have used data from the British Thoracic Society …