Mycobacterium marinum is a waterborne mycobacterium that commonly infects fish and amphibians worldwide, but transmission to humans can occasionally occur, typically as a granulomatous skin infection following minor hand trauma. Infection involving the lungs is very rare. We herein describe a case of M. marinum-associated pneumonia and pneumothorax.
In August 2008, an 81-year-old man was admitted to a hospital for detailed examination of weight loss and an abnormal shadow on chest imaging. Based on a sputum test, nontuberculous mycobacteriosis caused by M. marinum was diagnosed. At that time, the blood chemistry revealed no respiratory symptoms or inflammatory findings, and the patient was treated on an outpatient basis with erythromycin and an expectorant. In late November 2008, sputum and coughing were observed. Furthermore, the patient developed a fever and chest pain that increased while breathing and he visited the emergency outpatient unit of our hospital on December 1. Hypoxemia, bilateral pneumonia, and right pneumothorax were observed, and a chest tube was inserted into the right thoracic cavity. Results of an acid-fast bacteria smear from the sputum and pleural effusion were positive, and M. marinum was identified on culture. The patient was diagnosed as having a lung infection complicated by pneumothorax caused by M. marinum. The lung infection was ameliorated with clarithromycin, rifampicin and ethambutol. However, no decreased in the air leaking from the chest tube was noted and inflation of the lung was incomplete. The department of respiratory surgery therefore performed thoracoplasty and lung cerclage. Subsequently, the air leak subsided, allowing removal of the chest tube and the patient was discharged.
