Biologically active isoniazid (INH) levels in plasma have been assayed by the tube dilution method
1 or by the vertical diffusion method
2, 3 using human tubercle bacillus as the test organism. The cylinder plate method has been widely used as the standard procedure for the assay in the antibiotic field, because of its simplicity and accuracy. UMEZAWA
et al4 reported using this method with mycobacteria 607 as the test organism. This only assays INH in the ranges over 8 μg/ml and was thus useless for clinical purposes.
In the present paper, the authors intend to report their studies
6, 7, 8, 9 of the assay method for biologically active INH in body fluids by the thin agar cylinder plate method' using rapidly growing, INH highly sensitive acid-fast bacterium as, test organism.
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