MADISON BM, GEORGE I, GROSS W, LIPMAN H, MAZUREK J, METCHOCK B, ROBINSON-DUNN B, SLOUTSKY A, SAMONS L, RIDDERHOF JC; Interscience Conference on Antimicrobial Agents and Chemotherapy.
Abstr Intersci Conf Antimicrob Agents Chemother Intersci Conf Antimicrob Agents Chemother. 1999 Sep 26-29; 39: 204 (abstract no. 866).
CDC, Atlanta, GA
Isoniazid (INH) is an important drug for the treatment of tuberculosis (TB). Resistance to INH is more common than resistance to other drugs. Therapy with INH may be effective in patients with isolates that have "low-level" INH resistance; however, most laboratories only test one concentration of INH in BACTEC and, thus cannot determine the level of resistance. In addition, there are few data on the reproducibility of INH results between methods and laboratories. In this study, four laboratories provided routine susceptibility data that included results of testing by BACTEC and re-testing resistant (R) isolates using the agar proportion (AP) method. Resistance was detected by BACTEC in isolates from 12.5 % (87/696) of patients. Of 63 isolates R at 0.2 ug/ml in AP, 27 (42.9%) were low-level resistant (i.e., S at 1.0 ug/ml in AP). Resistance in BACTEC (0.1 ug/ml) was confirmed at 0.2 ug/ml in AP for 92.2 % (83/90) of the isolates. Of isolates that were R at 0.4 ug/ml in BACTEC, 83.8% (31/37) confirmed at the equivalent concentration of 1.0 ug/ml in AP. Of 24 isolates tested by BACTEC with INH at 0.1 ug/ml, there was inter-laboratory agreement on 20/24 of the isolates. These data suggest that many isolates have low-level resistance, and testing two concentrations of INH may provide helpful information to clinicians. There is good agreement(>95%) between the critical concentrations of INH between BACTEC and AP, but there is less agreement (<85%) for the higher concentrations of drug.
Publication Types:
Keywords:
- Agar
- Disease Susceptibility
- Drug Administration Routes
- Evaluation Studies
- Humans
- Isoniazid
- Mycobacterium tuberculosis
- Physical Examination
- Research Design
- Tuberculosis
- methods
Other ID:
UI: 102245221
From Meeting Abstracts