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Disease caused by environmental mycobacteria

Chapter:
Disease caused by environmental mycobacteria
Author(s):

J. van Ingen

and P.D.O. Davies

DOI:
10.1093/med/9780199204854.003.070626_update_001

Update:

Chapter heavily revised.

Updated on 31 May 2012. The previous version of this content can be found here.

Introduction—there are over 130 species of mycobacteria; species other than M. tuberculosis complex and M. leprae are collectively referred to as the nontuberculous or environmental mycobacteria. Nontuberculous mycobacteria (NTM) are divided into two groups, the slow growers and the rapid growers. The most common organisms causing human disease are the slow-growing species M. avium complex and M. kansasii and, less commonly, M. marinum, M. xenopi, M. simiae, M. malmoense, and M. ulcerans. The rapid growers that are human pathogens are M. abscessus, M. fortuitum, and M. chelonae.

Ecology and epidemiology—NTM are ubiquitous in the environment and have been isolated from water, soil, domestic and wild animals, milk, and food products. Transmission to humans is though inhalation, ingestion, or traumatic inoculation. The prevalence of NTM infections is likely to have been underestimated, and appears to be increasing in developed countries.

Clinical features—four clinical syndromes have been described: (1) pulmonary disease; (2) lymphadenitis; (3) postinoculation mycobacteriosis; (4) disseminated disease. Cervical lymphadenitis is the most common presentation in children whereas chronic pulmonary disease is more frequent in adults.

Diagnosis—microscopic examination using acid fast stains and culture on appropriate media remain the cornerstone of diagnosis. The use of techniques such high performance liquid chromatography (HPLC), polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis and 16S ribosomal DNA sequencing have enabled more accurate speciation of nontuberculous mycobacteria.

Treatment—this depends on the site and severity of the infection, the presence of predisposing conditions, and the species of mycobacterium. Therapy of disease due to slow growers is usually based on regimens containing clarithromycin or azithromycin; that for rapid growers is largely empirical. Antiretroviral therapy is more beneficial than antimycobacterial agents in patients with AIDS-related disease.

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