Mycobacteriosis: the most common causative agents.

The annual number of diagnosed diseases caused by non-tuberculous mycobacteria in predisposed individuals remains constant in the Czech Republic. Their clinical characteristics vary depending on the properties of the causative species and its presence and quantity in the immediate environment of the patient. The most common clinically relevant species are Mycobacterium avium, M. kansasii, and M. xenopi. The most important source of M. avium is peat and products derived from it. M. avium may colonise warm water systems, posing a high risk of exposure to users (jacuzzi users in particular). M. kansasii is still present in waters of areas affected by industrial and mining activities. Its recently isolated genetic variants are mostly of no clinical significance but may be present as contaminants in medical preparations. M. xenopi permanently colonises most warm water systems, and its practical ubiquity makes difficult the interpretation of ambiguous findings on imaging. The antibiotic treatment, which may not always be successful, should be initiated after a comprehensive assessment of the patient's condition, imaging data, and disease progression. Similarly, the results of laboratory tests may not always be authoritative in decision making.