Efficacy of a multiplex bacterial PCR in identifying pathogens in pleural empyema

Abstract

Introduction: The identification of the pathogens involved in pleural empyema has mainly relied on conventional bacterial culture or single species polymerase chain reaction (PCR), both with relatively low sensitivity. We investigated the efficacy of a commercial multiplex pneumonia PCR assay to identify the pathogens involved in pleural empyema. Methods: Prospective, monocentric, observational study. Pleural fluid samples collected from 194 consecutive patients were analysed at the time of hospitalisation using conventional microbiology. Commercial multiplex pneumonia bacterial PCR was performed retrospectively. Results: There was a suspicion of empyema based on ultrasound findings in 18.5% of the cases, of these, 85.7% were diagnosed with empyema. When only taking into account the pathogens included in the multiplex PCR assay more pathogens were identified using the multiplex PCR assay than with conventional methods (23.3% vs. 6.7%, p=0.008). In those cases without suspicion of empyema, 9.7% had a final diagnosis of empyema. Using the same criteria, conventional methods identified pathogens in 0% of the cases and the multiplex PCR-based assay identified pathogens in 6.7% of the cases. The most common microorganisms identified in the cases diagnosed with empyema, were anaerobes (31) followed by gram-positive cocci (10) and gram-negative rods (4). Conclusion: The multiplex PCR-based assay had a higher sensitivity and specificity than conventional microbiology when only the pathogens on the panel were taken into account. A dedicated pleural empyema multiplex PCR panel including anaerobes would be needed to cover most common pathogens involved in pleural infection.