This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Starks, A. M. Articles by Posey, J. E. Search for Related Content PubMed PubMed Citation Articles by Starks, A. M. Articles by Posey, J. E.

 Previous Article  |  Next Article 

Antimicrobial Agents and Chemotherapy, March 2009, p. 1061-1066, Vol. 53, No. 3
0066-4804/09/$08.00+0     doi:10.1128/AAC.01357-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Mutations at embB Codon 306 Are an Important Molecular Indicator of Ethambutol Resistance in Mycobacterium tuberculosis

Angela M. Starks, Aysel Gumusboga, Bonnie B. Plikaytis, Thomas M. Shinnick, and James E. Posey^*

Division of Tuberculosis Elimination, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia 30333

Received 9 October 2008/ Returned for modification 10 November 2008/ Accepted 12 December 2008

Ethambutol resistance in clinical Mycobacterium tuberculosis isolates is associated primarily with missense mutations in the embB gene. However, recent reports have described the presence of embB mutations, especially those at embB codon 306, in isolates susceptible to ethambutol. To clarify the role of embB mutations in ethambutol resistance, we sequenced the ethambutol resistance-determining region in spontaneous ethambutol-resistant mutants. In our study, 66% of spontaneous mutants contained a single point mutation in embB, with 55% of these occurring at embB 306. The MIC of ethambutol for spontaneous mutants was increased two- to eightfold relative to the pansusceptible M. tuberculosis strains from which the mutants were generated. To further characterize the role of embB 306 mutations, we directly introduced mutant alleles, embB(M306V) or embB(M306I), into pansusceptible M. tuberculosis strains and conversely reverted mutant alleles in spontaneous ethambutol-resistant mutants back to those of the wild type via allelic exchange using specialized linkage transduction. We determined that the MIC of ethambutol was reduced fourfold for three of the four spontaneous ethambutol-resistant embB 306 mutants when the mutant allele was replaced with the wild-type embB allele. The MIC for one of the spontaneous mutants genetically reverted to wild-type embB was reduced by only twofold. When the wild-type embB allele was converted to the mutant allele embB(M306V), the ethambutol MIC was increased fourfold, and when the allele was changed to M306I, the ethambutol MIC increased twofold. Our data indicate that embB 306 mutations are sufficient to confer ethambutol resistance, and detection of these mutations should be considered in the development of rapid molecular tests.

---

* Corresponding author. Mailing address: 1600 Clifton Rd. NE, Bldg. 17, Room 4029, M/S F08, Atlanta, GA 30333. Phone: (404) 639-1712. Fax: (404) 639-1287. E-mail: jposey{at}cdc.gov

Published ahead of print on 22 December 2008.

Present address: Institute of Tropical Medicine, Nationaalstraat 155, B-2000 Antwerp, Belgium.

---

Antimicrobial Agents and Chemotherapy, March 2009, p. 1061-1066, Vol. 53, No. 3
0066-4804/09/$08.00+0     doi:10.1128/AAC.01357-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Goude, R., Amin, A. G., Chatterjee, D., Parish, T. (2009). The Arabinosyltransferase EmbC Is Inhibited by Ethambutol in Mycobacterium tuberculosis. Antimicrob. Agents Chemother. 53: 4138-4146 [Abstract] [Full Text]