[Treatment outcomes of multidrug-resistant tuberculosis--comparison between success and failure cases]

The thirty-two times of treatment in 27 patients with multidrug-resistant tuberculosis (MDR-TB) were analyzed retrospectively. In twenty-eight times of treatments cases had previous histories of antituberculosis chemotherapy. Drug sensitivity tests were performed by Microtiter method for isoniazid (INH), rifampicin (RFP), ethambutol, streptomycin, kanamycin, enviomycin, ethionamide, para-aminosalicylic acid and cycloserine. A drug is defined as 'active drug' when the drug was proved to be sensitive by the drug sensitivity tests or never used in the past or used for not more than 2 months in case of pyrazinamide (PZA) and less than one month for fluoroquinolones. Outcomes of treatments were grouped as follows; A: bacteriologically negative for more than 24 months, B: bacteriologically negative for more than 6 months but less than 24 months, C: bacteriologically relapsed after negative conversion, D: continuously bacilli positive for M. tuberculosis. Mean age of patients in each group were; 61.0 yrs for group A (n = 10), 61.0 yrs for group B (n = 7), 52.5 yrs for group C (n = 4), 57.9 yrs for group D (n = 11). All patients had cavitary disease and positive sputum smears for acid-fast bacilli. Mean numbers of 'active drugs' used per treatment in each group, were 3.6, 3.3, 2.5 and 1.8 respectively, while the mean number of resistant drug including INH and RFP were 2.8, 3.3, 2.5 and 3.7. The number of drugs, which was unable to use due to toxicity, were 0.20, 0.14, 0.50, and 0.73 per treatment respectively. All of 9 patients treated with four 'active drugs' were in group A or B and succeeded to achieve negative conversion. The duration of chemotherapy in group A was 13 to 44 months. Treatment had failed in 4 out of 11 patients treated with 3 'active drugs' and 11 out of 12 patients treated with less than 2 'active drugs'. Fluoroquinolones (ofloxacin, levofloxacin or sparfloxacin) were used in 7 out of 10 patients in group A and in 6 out of 9 patients treated with four-drug regimens while they were used only in 3 out of 11 patients in group D. Regimens with at least 4 sensitive drugs are mandatory for the successful treatment of MDR-TB and fluoroquinolones are needed in the majority of cases to ensure the four-drug regimen, because of frequent drug resistance or toxicity to other antituberculosis drugs.