Characteristics and treatment outcomes of INH-resistant or RFP-resistant tuberculosis

As an effective regimen for isoniazid-resistant but rifampicin-susceptible tuberculosis (INHr-TB), the use of a 6-month three or four-drug treatment regimen including refampicin (or rifampin) and pyrazinamide has been recommended by many experts of the world. On the other hand, treatment regimen for rifampicin-resistant but isoniazide-susceptible tuberculosis (RFPr-TB) has not been well established because of the small number of such patients. In Japan the standard regimen has not been established even for INHr-TB, and the treatment has been done by each physician on the empirical bases. To determine the adequate therapy of INH-resistant TB or RFP-resistant TB. Retrospective cohort study. SUBJECTIVES: Hundred and eleven INHr-TB patients (4.9%) and 5 RFPr-TB patients (0.2%) out of 2252 new smear-positive tuberculosis patients who were admitted to our hospital from 1994 to 1998. Patients with previous tuberculosis history was found in 35 of 111 INHr-TB (31.5%) patients, of which 13 (37.1%) were re-treated within 3 years. On the other hand 146 patients (21.1%) of all new culture-positive tuberculosis patients (N = 690) treated in our hospital from 1997 to 1999 had the previous tuberculosis history of which only 8 patients (5.5%) were retreated within 3 years while 115 patients relapsed more than 10 years after the onset of previous tuberculosis history. The frequency of recurrence within 3 years after the onset of previous tuberculosis history was, significantly higher (p < 0.0001) in cases of INHr-TB (13/111 [11.7%]) than in cases of newly registered ones (8/690 [1.2%]), and the fact indicates that the incidence of tuberculosis recurrence was higher in INHr-TB patients than in pan-sensitive TB patients when the previous treatment was discontinued or insufficiently implemented. The resistance pattern of the INHr-strains were as follows. INH alone 40 (36.0%), SM-resistant 47 (42.3%), TH resistant 19 (17.1%), EB-resistant 18 (16.2%), KM-resistant 6 (5.4%), and others 3 (2.7%). Therefore the mean number (+/- SD) of resistant drugs excluding INH was 1.4 +/- 0.7. Eighteen out of 71 (25.4%) strains with low grade INH-resistance (0.1 microgram/ml complete resistance) had also TH-resistance, while only one out of 40 (2.5%) strains with high grade INH-resistance (1 microgram/ml resistance) was resistant to TH (p = 0.005). Of 111 INHr-TB patients, 9 patients (8.1%) discontinued treatment by themselves, 17 patients (15.3%) admitted to another hospital, and 17 patients (