Purpose: Non tuberculous mycobacterial (NTM) infections, also called atypical mycobacterial infections, are caused by environmental mycobacteria and usually occur in cases of general or local immunosupression. These infections usually concern the lungs, the lymphatic system, the skin or the bones tissues. They are sometimes disseminated. In spite of new efficient antibiotics, including macrolides, therapeutic failures are common and favoured by long treatments with their potential adverse effects and drug interactions.

Current knowledge and key points: The prevalence of atypical mycobacterial infections is increasing and is also observed in internal medicine and geriatric wards. Their clinical expression can be varied. Nowadays, these infections are more and more frequent in non-infected HIV patients, whether immunosupressed or not. Concerning other localisations of atypical mycobacterial infections, iatrogenic causes seem to be increasing and cases of nosocomial transmissions have also been described. When a NTM is found in a sample, its role in the cause of an infection must be assessed with criterias distinguishing infection from colonisation.

Future prospects and projects: For those who are not locally or generally immunosupressed, it is important to search for an immunological deficiency. Indeed, patients having congenital deficiencies occurring in the interferon and interleukine pathways can develop repeated NTM infections. Therefore, for pulmonary infections in treatment failure and for disseminated infections, an adjuvant treatment by interferon gamma could be proposed. New molecules have recently been tested and can be used in some atypical mycobacterial infections.