Significance of microbiological and biochemical analyses in empyema thoracis

Following the indifferent results of a retrospective analysis, a prospective study was undertaken to analyse the causative organisms in 51 cases of empyema. Cultures were positive in 44/51 (= 86.3%) cases. 2 bacterial species were recovered for each empyema. The aerobic gram-positive cocci represented the largest group (57%), followed by aerobic gram-negative bacteria (18.6%), anaerobic bacteria (18.6%), and fungi (5.8%). Polymicrobial empyema accounted for 59.1% of the cases. Anaerobic bacteria were cultured from 36.4% of empyema. Anaerobic bacteria were more frequently isolated from pleural effusions than from other specimens. Swabs were found to be of minor value for anaerobics. Analyses of glucose and pH value in pleural effusions have been reported to be useful in differentiating complicated from uncomplicated effusions in cases where the aspirated fluid is not purulent and is negative on gram stain, but clinical as well as radiological findings point to an empyema. Our results have shown that pH-values less than 7.30 and Glucose less than 60 mg/dl were not absolutely specific for empyema. In contrast, PMN-elastase in pleural effusion and HI-30 in urine showed a statistically significant differentiation of empyema from exudates of other origin.