JB
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Karunakaran, P.
Right arrow Articles by Davies, J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Karunakaran, P.
Right arrow Articles by Davies, J.

 Previous Article  |  Next Article 

Journal of Bacteriology, June 2000, p. 3331-3335, Vol. 182, No. 12
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Genetic Antagonism and Hypermutability in Mycobacterium smegmatis

Ponniah Karunakarandagger and Julian Davies*

Department of Microbiology and Immunology, The University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada

Received 27 October 1999/Accepted 31 March 2000

Multidrug-resistant strains of Mycobacterium tuberculosis are a serious and continuing human health problem. Such strains may contain as many as four or five different mutations, and M. tuberculosis strains that are resistant to both streptomycin and rifampin contain mutations in the rpsL and rpoB genes, respectively. Coexisting mutations of this kind in Escherichia coli have been shown to interact negatively (S. L. Chakrabarti and L. Gorini, Proc. Natl. Acad. Sci. USA 72:2084-2087, 1975; S. L. Chakrabarti and L. Gorini, Proc. Natl. Acad. Sci. USA 74:1157-1161, 1977). We investigated this possibility in Mycobacterium smegmatis by analyzing the frequency and nature of spontaneous mutants that are resistant to either streptomycin or rifampin or to both antibiotics. Mutants resistant to streptomycin were isolated from characterized rifampin-resistant mutants of M. smegmatis under selection either for one or for both antibiotics. Similarly, mutants resistant to rifampin were isolated from streptomycin-resistant strains. The second antibiotic resistance mutation occurred at a lower frequency in both cases. Surprisingly, in both cases a very high rate of reversion of the initial antibiotic resistance allele was detected when single antibiotic selection was used; the majority of strains resistant to only one antibiotic were isolated by this process. Determinations of rates of mutation to antibiotic resistance in M. smegmatis showed that the frequencies were enhanced up to 104-fold during stationary phase. If such behavior is also typical of slow-growing pathogenic mycobacteria, these studies suggest that the generation of multiply drug-resistant strains by successive mutations may be a more complex genetic phenomenon than suspected.

* Corresponding author. Mailing address: Department of Microbiology and Immunology, The University of British Columbia, 6174 University Blvd., Vancouver, B.C. V6T 1Z3, Canada. Phone: (604) 822-8883. Fax: (604) 822-6041. E-mail: jed{at}unixg.ubc.ca.

dagger Present address: University of British Columbia Centre for Disease Control, Vancouver, British Columbia V5Z 4R4, Canada.

Journal of Bacteriology, June 2000, p. 3331-3335, Vol. 182, No. 12
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
Appl. Environ. Microbiol. Infect. Immun. Eukaryot. Cell
Mol. Cell. Biol. J. Virol. Microbiol. Mol. Biol. Rev.
ALL ASM JOURNALS

Copyright © 2000 by the American Society for Microbiology. All rights reserved.