INTRODUCTION:The diagnosis of nontuberculous mycobacterial (NTM) disease is especially difficult in patients with underlying chronic lung diseases. Mycobacterium szulgai is a rare cause of NTM lung disease. We present a patient with essentially untreated M. szulgai infection for at least nine years resulting in severe cavitary lung disease.
CASE PRESENTATION:The patient is a 58 year old man with COPD referred in January 2006 with cavitary lung disease, chronic intermittent fevers, night sweats, and a productive cough. He had lost 25 pounds unintentionally over the last 18 months. The patient recalled taking five drug therapy for tuberculosis many years ago but had discontinued therapy after two weeks. He had rare and erratic medical follow-up and received no other treatment. A PPD skin test in September 2005 was negative. A chest radiograph revealed extensive, predominantly left sided cavitary lung disease. An older film from 2001 was obtained and revealed only a solitary moderate sized cavitary lesion in the left lung apex. Expectorated sputum was smear positive for AFB and he was started on four drug anti-tuberculous therapy. Subsequently, his previous records were obtained revealing growth of M. szulgai from sputum in 1997. The organism was sensitive to ethambutol, rifampin, clarithromycin, ciprofloxacin, and high doses of INH, cycloserine and streptomycin. Based on MICs, he was placed on clarithromycin (500 mg BID) and ethambutol (1200 mg daily). The AFB cultures eventually grew 4+ M. szulgai at two weeks. After three months of treatment, he reported complete resolution of his systemic symptoms and had regained 25 pounds. Follow up chest radiographs demonstrated clearing of the parenchymal infiltrates, but with persistent volume loss and cavitary lesions. Repeat AFB cultures after three months of treatment were negative. He continues on two drug therapy with plans to complete a year of therapy after his cultures have turned negative.
DISCUSSIONS:Mycobacterium szulgai is a very rare pathogen with only about 36 cases of pulmonary disease reported in humans. It represents <0.5% of all NTM isolates and is primarily a pulmonary pathogen, although isolated from other sites. The typical patient is a middle aged man with risk factors including smoking, alcohol and COPD (1). It is usually associated with disease, and therefore requires therapy whenever isolated and should not be considered a contaminant or colonizer. This case represents the longest known period of essentially untreated M. szulgai infection (1997-2006) and highlights the indolent yet progressive nature of this infection. The optimum treatment regimen for M. szulgai is not established. Historically, it is known to respond well to anti-tuberculous treatment, in three and four drug combinations, with some reporting success with two drugs. Fluoroquinolones and macrolides also have reported efficacy. Our patient has had a good clinical, radiologic and microbiologic response with a two drug regimen of clarithromycin and ethambutol. Brown and colleagues found clarithromycin to have MICs of 0.5 μg/ml against 100% of M. szulgai (2).
CONCLUSION:M. szulgai lung infection can have an indolent yet progressive course. Its isolation is uniformly associated with disease and therefore requires treatment. Clarithromycin seems particularly effective and should be considered as part of the treatment regimen for M. szulgai lung disease.
DISCLOSURE:Kanwaldeep Randhawa, No Financial Disclosure Information; No Product/Research Disclosure Information