Bacteriology of complicated parapneumonic effusions

Purpose of review The bacteriology of complicated parapneumonic effusions has changed in recent decades, but the causative organisms often remain obscure in up to 40% of cases. Recently, new molecular methods have become available which might help clinical management and improve our understanding of this condition. In this review, we will consider the current bacteriological spectrum of pleural infection and look at some of the new molecular methods. Recent findings Hospital-acquired pleural infection exhibits a different bacteriology than pleural infection originating in the community. It carries a significantly higher mortality and requires different antibiotics at presentation. Streptococcal and anaerobic infections have low associated mortalities whereas staphylococcal, enterobacterial and mixed aerobic infections carry a worse prognosis. The yield of causative organisms can be significantly increased by the use of bacterial nucleic acid amplification and this may have a role in routine clinical practice in the near future. Summary The bacteriology of pleural infection has changed markedly in recent years. Mortality is highest with hospital-acquired pleural infection and infections caused by staphylococci, Enterobacteriacae and mixed aerobes. New molecular microbiological methods substantially increase bacterial yield in pleural fluid.