Empyema: do we know enough?

Abstract

Introduction Pleural empyema is an uncommon but serious condition defined by infected fluid in the pleural space. These patients are often given long courses of empirical broad-spectrum antibiotics as the yield from conventional culture methods is notoriously low. The literature shows that with conventional culture methods of the pleural fluid up to 40-60% of causative pathogens remain unidentified. In recent years methods such as DNA analysis have been developed in an attempt to increase identification rates of pathogens. This paper aims to review the literature to determine the additional benefit of DNA analysis methods above conventional culture of fluid in pleural empyema. Methods A review of the literature searching for studies investigating bacteria present in pleural fluid in patients with empyema was carried out. Studies in which adult patients had a diagnosis of empyema and where conventional culture and molecular methods were used to identify the causative bacteria were included. Descriptive statistics were used to compare the increased yield from molecular methods. Results Five studies which compared conventional culture techniques and molecular methods for identification of the pathogen in pleural empyema cases were identified. The mean culture-positive rate and molecular-positive rate in these studies was 37.5% (range 10-58%) and 80.0% (range 22.5-82%) respectively. All the studies concluded that molecular techniques provided a greater identification rate than conventional culture techniques. Conclusion Pleural empyema is often culture negative leading to broad-spectrum antibiotic use. This review shows that molecular methods significantly increase the yield of causative bacteria present in pleural fluid.