COMPARISON OF CHARACTERISTICS OF PATIENTS AND TREATMENT OUTCOME FOR PULMONARY NONTUBERCULOUS MYCOBACTERIAL INFECTION AND PULMONARY TUBERCULOSIS

Background - Patients with non-tuberculous mycobacteria are usually st arted on conventional antituberculous triple therapy once acid fast ba cilli are detected, before the exact type of mycobacteria has been ide ntified. The ability to identify the characteristics of patients with tuberculous and non-tuberculous mycobacteria may be helpful in identif ying before treatment those patients more likely to have non-tuberculo us infection. Methods - A retrospective study was conducted of all pat ients in one unit in whom non-tuberculous mycobacteria were identified in sputum or bronchoalveolar washings in the period 1987-93. The patt ern of drug resistance was determined from laboratory records, and all case notes and chest radiographs were reviewed to identify the underl ying disease and treatment outcome. All cases were compared with a mat ched control group of patients with culture positive Mycobacterium tub erculosis diagnosed during the same period. Results - In the period st udied there were 70 non-tuberculous and 221 tuberculous isolates. The non-tuberculous bacteria were typed as follows: M xenopi 23 (33%), M k ansasii 19 (27%), M fortuitum 14 (20%), others 14 (20%). Of those with nontuberculous mycobacteria, 83% were white subjects compared with 47 % for tuberculosis. Patients with non-tuberculous mycobacteria were ol der than those with tuberculosis. Pre-existing lung disease or AIDS wa s present in 81% of patients with non-tuberculous mycobacteria and in 17% of patients with tuberculosis. Sensitivity to rifampicin and etham butol was seen in 95% of M xenopi and 96% of M kansasii isolates. Rela pse occurred in 60% of cases infected with M xenopi, 20% infected with M kansasii, and in 7% of cases with tuberculosis. Conclusions - In th e population studied non-tuberculous mycobacteria occurred most freque ntly in elderly white subjects with pre-existing lung disease. If myco bacteria are detected in this group, consideration should be given to the possibility of non-tuberculous infection before embarking on treat ment. A combination containing rifampicin and ethambutol is effective. The relapse rate for infection with M xenopi is high and prospective studies of the effect of the above combination of antituberculosis dru gs are needed.