The prevalence of Mycobacterium tuberculosis drug resistance in New Caledonia, 1995-1996.

Setting: Study of the susceptibility to anti-tuberculosis drugs of Mycobacterium tuberculosis strains isolated in New Caledonia, a French South Pacific Territory, where tuberculosis continues to be a public health problem.

Objective: To assess the stability of this susceptibility in order to justify both non-systematic susceptibility testing and the implementation of simplified chemotherapy regimens.

Methods: Over a period of nearly 2 years (1995-1996), every new case of tuberculosis confirmed by the laboratory was included in the study. A total of 105 strains were tested against five anti-tuberculosis drugs: isoniazid, rifampicin, ethambutol, pyrazinamide and streptomycin.

Results: No primary drug resistance was detected for the main drugs. One strain with acquired resistance to isoniazid and streptomycin was isolated from one of the 12 patients suffering a relapse of the disease.

Conclusions: The results of this exhaustive study justify the non-systematic approach to susceptibility testing for new patients. However, for strains isolated from patients suffering from relapse or therapeutic failure, or who belong to a high risk population, drug susceptibility testing should be performed. This kind of management will aid in the detection of possible isoniazid and streptomycin resistance, thus avoiding the selection and possible emergence of strains resistant to rifampicin. The results of the study argue for the use of a fixed dose regimen using triple combination tablets of isoniazid, rifampicin and pyrazinamide (HRZ) for 2 months, followed by dual drug therapy (HR) for 4 months.