[Risk of acquisition of RFP resistance out of INH resistant RFP susceptible tuberculosis].

OBJECTIVE: To investigate the prognosis of isoniazid (H) resistant rifampicin (R) susceptible tuberculosis cases with emphasis on the risk factors of developing MDR.

METHOD: Retrospective review of H resistant R susceptible tuberculosis cases that were treated at Fukujuji Hospital in Japan between 1990 and 2000.

RESULTS: Four cases developed drug resistance and became MDR. Seventy seven cases completed treatment with bacteriological confirmation of negativity during treatment and 2 years after treatment (cure). Other 38 cases completed treatment with confirmation of culture negativity at the end of treatment but one of them relapsed within 2 years and the remaining 37 cases were not followed up for 2 years. Fourteen cases died, 13 cases defaulted and 17 cases were transferred out. The comparison of the regimen of chemotherapy between cured cases and cases who became MDR showed that more cured cases were found among those who started treatment with 4 drugs or more than cases who started treatment with 3 drugs or less. Other factors that were related (but not significant) to cure rate were non-diabetics in comparison with diabetics and 4 drug standard regimen (HRZS, HRZE) in comparison with 3 drug standard regimen (HRS, HRE).

DISCUSSION: Prevention of MDR could be achieved by wider use of 4-drug standard regimen and changes of chemotherapy regimen promptly responding to the results of drug susceptibility tests.