Diagnosis and treatment of disease caused by nontuberculous mycobacteria.

1. Staining and culture. Current methods of specimen staining and culture used for M. tuberculosis are acceptable for most NTM species. The preferred methodology includes fluorochrome staining and culture in a liquid medium as well as on Middlebrook 7H10 or 7H11 agar. Species for which special growth conditions are needed include those responsible for cutaneous disease, which need lower incubation temperatures, and the relatively fastidious species M. haemophilum, M. genavense , and M. conspicuum . 2. Species identification. Methods of rapid species identification including commercial DNA probes ( M. avium complex, M. kansasii, M. gordonae ) and high-pressure liquid chromatography are preferred over the slower traditional biochemical methods. 3. Susceptibility testing of M. avium complex. Susceptibility testing with rifabutin and the antituberculosis drugs is not recommended. Routine testing against clarithromycin should not be performed, but that test should be performed on isolates from patients who have failed prior macrolide therapy or prophylaxis. Minimal inhibitory concentration (MIC) of . 32 m g/ml is the recommended resistance breakpoint. 4. Susceptibility testing of M. kansasii. Routine susceptibility testing of M. kansasii should include only rifampin, because currently used resistance breakpoints for isoniazid and streptomycin often give misleading results and methods for the other drugs have not been established. 5. Susceptibility testing of the rapid growers. Susceptibility testing of clinically significant rapidly growing mycobacteria ( M. fortuitum, M. abscessus, M. chelonae ) should not be performed with the antituberculosis agents. They should be tested against antibacterial drugs including amikacin, doxycycline, imipenem, the fluorinated quinolones, a sulfonamide, cefoxitin, and clarithromycin.