[Empyema due to Actinomyces: a diagnostic challenge].

a diagnostic challenge. Isolated pleural effusion due to actinomycosis is rare and poses a diagnostic challenge to clinicians not only because it is uncommon and often forgotten, but also because culture of the causative microorganism is technically difficult. The classic al microscopic appearance of this Gram-positive bacillus on cultures often forms the basis of diagnosis. This is the report of a case of massive left sided pleural effusion due to Actinomyces israelii that improved clinically and radiologically after surgery and prolonged antibiotic treatment.