Bacteriological aetiology and antimicrobial treatment of pleural empyema

Our aims were to describe the aetiologies of culture-positive pleural infections and to evaluate the choice of empiric antimicrobial treatment regimens according to antimicrobial sensitivity, and to evaluate the possible influence of this on outcome.

All cases over a 9-y period were identified from 3 hospitals using the laboratory databases of the clinical microbiology departments, and were verified by evaluating the medical records.

We identified 291 isolates in pleural fluid cultures from 158 patients. These included viridans streptococci (25%), Staphylococcus aureus (18%), anaerobic bacteria (17%), Enterobacteriaceae (12%), Staphylococcus epidermidis (10%), and Streptococcus pneumoniae (7%), with differences between nosocomial and community-acquired infections. The mortality (overall 27%) was highest among the patients with Enterobacteriaceae (50%) and S. aureus (36%) infections, and in patients with mixed infections (34%). The actual empiric treatment or the recommended penicillin plus metronidazole had low antimicrobial coverage (49%) compared to the proposed cefuroxime plus metronidazole (78%). Thoracentesis was often delayed (median 2 days). The adequacy of empiric antimicrobial therapy was independently correlated with mortality (odds ratio 0.43, 95% confidence interval 0.30-0.62).

The early diagnosis of pleural infection could be optimized. In this North-European patient population, we suggest that the recommended empiric antimicrobial treatment be changed to cefuroxime plus metronidazole for community-acquired and nosocomial infections.