Section 6
Chapter 5,642

Improved method for testing susceptibility of Mycobacterium tuberculosis to pyrazinamide

Butler, W.R.; Kilburn, J.O.

Journal of Clinical Microbiology 16(6): 1106-1109


ISSN/ISBN: 0095-1137
PMID: 6819309
Accession: 005641886

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The acid medium required to test susceptibility of Mycobacterium tuberculosis to pyrazinamide (PZA) is a major problem in obtaining reliable test results. Satisfactory growth is usually obtained on Middlebrook and Cohn 7H10 medium at pH 5.5 if albumin-dextrose-catalase (ADC) supplement rather than oleic acid-albumin-dextrose-catalase is used; however, some lots of ADC supplement still fail to support growth at this low pH. A rapid turbidimetric test was developed to determine the growth-supporting potential of ADC enrichment for M. tuberculosis at pH 5.5. An atmosphere supplemented with 5 to 10% carbon dioxide, used to stimulate growth of tubercle bacilli on 7H10 medium, counteracted the growth-inhibiting effects of PZA. By using optimum conditions of medium and pH, the susceptibility of 90% of M. tuberculosis strains to PZA was determined.

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