抗結核剤の耐性問題第2部: 臨床耐性限界その1. Rifampicin

抄録

Preliminary studies showed that some strains of tubercle bacilli were inhibited even by2, μg/ml of rifampicin (RFP), but 10μg/ml or higher concentrations were needed for theinhibition of all strains. Of 5, 100 patients with pulmonary tuberculosis who were admittedto our hospital during 12 years since January 1970 through 1981, 1, 344 patients had noprevious antituberculous drug therapy. All of the strains of Mycobacterium tuberculosisisolated from such 1, 344 patients showed no or less than 10% growth of control on 10 μg-RFP medium by indirect susceptibility tests. But, I defined the clinically applicable criteriaof resistance to RFP as “more than 1 % growth of control on 10μg-RFP medium” becauseof following reasons: 1) the growth more than 1% and less than 10% of control on 10μg-RFP medium could be reasonably explained as the results of some technical failures, 2) theresults of follow-up observations of respective cases, 3) our previous studies on thedistribution of RFP-susceptibility of natural resistant strains.
Among total 5, 100 cases, 605 cases had been treated with antituberculous drugspreviously but failed to achieve negative conversion of the bacilli, and restarted thetreatment with regimen including RFP (retreatment group), and the remains had noprevious treatment (initial treatment group). The negative conversion rates within threemonths of treatment were almost same (more than 95%) in both groups, but the rates ofRFP-resistance were 5.6% for the initial treatment group and 92.8 % for the retreatmentgroup.