The effect of growth rate on pyrazinamide activity in Mycobacterium tuberculosis - insights for early bactericidal activity?

Pullan, Steven T., Allnutt, Jon C., Devine, Rebecca, Hatch, Kim A., Jeeves, Rose E., Hendon-Dunn, Charlotte L., Marsh, Philip D. and Bacon, Joanna (2016) The effect of growth rate on pyrazinamide activity in Mycobacterium tuberculosis - insights for early bactericidal activity? BMC Infectious Diseases, 16. ISSN 1471-2334

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Background: Pyrazinamide (PZA) plays an essential part in the shortened six-month tuberculosis (TB) treatment course due to its activity against slow-growing and non-replicating organisms. We tested whether PZA preferentially targets slow growing cells of Mycobacterium tuberculosis that could be representative of bacteria that remain after the initial kill with isoniazid (INH), by observing the response of either slow growing or fast growing bacilli to differing concentrations of PZA. Methods: M. tuberculosis H37Rv was grown in continuous culture at either a constant fast growth rate (Mean Generation Time (MGT) of 23.1 h) or slow growth rate (69.3 h MGT) at a controlled dissolved oxygen tension of 10 % and a controlled acidity at pH 6.3 ± 0.1. Cultures were exposed to step-wise increases in the concentration of PZA (25 to 500 μgml−1) every two MGTs, and bacterial survival was measured. PZA-induced global gene expression was explored for each increase in PZA-concentration, using DNA microarray. Results: At a constant pH 6.3, actively dividing mycobacteria were susceptible to PZA, with similar responses to increasing concentrations of PZA at both growth rates. Three distinct phases of drug response could be distingished for both slow growing (69.3 h MGT) and fast growing (23.1 h MGT) bacilli. A bacteriostatic phase at a low concentration of PZA was followed by a recovery period in which the culture adapted to the presence of PZA and bacteria were actively dividing in steady-state. In contrast, there was a rapid loss of viability at bactericidal concentrations. There was a notable delay in the onset of the recovery period in quickly dividing cells compared with those dividing more slowly. Fast growers and slow growers adapted to PZA-exposure via very similar mechanisms; through reduced gene expression of tRNA, 50S, and 30S ribosomal proteins. Conclusions: PZA had an equivalent level of activity against fast growing and slow growing M. tuberculosis. At both growth rates drug-tolerance to sub-lethal concentrations may have been due to reduced expression of tRNA, 50S, and 30S ribosomal proteins. The findings from this study show that PZA has utility against more than one phenotypic sub-population of bacilli and could be re-assessed for its early bactericidal activity, in combination with other drugs, during TB treatment.

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Additional Information: This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.
Uncontrolled Keywords: pyrazinamide,chemostats,growth rate,gene expression,trans-translation,mycobacterium tuberculosis,sdg 3 - good health and well-being ,/dk/atira/pure/sustainabledevelopmentgoals/good_health_and_well_being
Faculty \ School: Faculty of Science > School of Biological Sciences
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Depositing User: Pure Connector
Date Deposited: 24 Sep 2016 00:08
Last Modified: 22 Oct 2022 01:21
DOI: 10.1186/s12879-016-1533-z


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