[Pulmonary infection caused by Mycobacterium gordonae (M. gordonae) in a healthy middle-aged male].

A 51-year-old man was admitted to our hospital in July 1989 because of an abnormality in his chest radiograph. On his yearly health check-up, an abnormality of his chest radiography was first noted in June 1988. At that time, examinations including bronchoscopy were performed but no specific diagnosis was made. On admission, his chest radiograph revealed new infiltrates at the apex of the right lung which were not present in June 1988. Three out of 5 consecutive sputum specimens after admission produced a pure growth of 100 colonies to 1+ of acid-fast bacilli (AFB). This AFB was scotochromogenic, and hydrolysis of Tween 80 at 5 days was positive. It did not reduce nitrate, and niacin test was negative. It was sensitive to ethambutol at a concentration of 5 micrograms/ml, and was not tolerant to 0.2% picric acid. We thus identified this AFB to be M. gordonae. The patient was treated with rifampicin (450 mg/day), isoniazid (400 mg/day), and ethambutol (1000 mg/day) for 9 months. After 2 months of treatment the sputum cultures became negative, and the chest radiograph showed improvement of the infiltrates. M. gordonae is considered to be one of the least pathogenic AFB to man. Most recent reports of M. gordonae infection have been in immunocompromized hosts or patients with a history of pulmonary tuberculosis. The present case is a very rare example of this organism affecting a healthy male, and thus yields new information on the pathogenesis of M. gordonae in man.