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Antimicrobial Agents and Chemotherapy, August 2009, p. 3353-3356, Vol. 53, No. 8
0066-4804/09/$08.00+0 doi:10.1128/AAC.00050-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Sequence Analyses of Just Four Genes To Detect Extensively Drug-Resistant Mycobacterium tuberculosis Strains in Multidrug-Resistant Tuberculosis Patients Undergoing Treatment 
,
Silke Feuerriegel,1*
Helen S. Cox,2
Nana Zarkua,3
Hamraev A. Karimovich,4
Kai Braker,5
Sabine Rüsch-Gerdes,1 and
Stefan Niemann1
Research Center Borstel, National Reference Center for Mycobacteria, Parkallee 18, 23845 Borstel, Germany,1 Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Victoria, Australia,2 Médecins Sans Frontières, Tashkent, Uzbekistan,3 Ministry of Health, Nukus, Karakalpakstan, Uzbekistan,4 Médecins Sans Frontières, Berlin, Germany5
Received 14 January 2009/ Returned for modification 29 March 2009/ Accepted 17 May 2009
The rapid detection of Mycobacterium tuberculosis isolates resistant to second-line drugs is crucial for the institution of appropriate treatment regimens as early as possible. Although molecular methods have successfully been used for the rapid detection of resistance to first-line drugs, there are limited data on mutations that confer resistance to second-line drugs. To address this question, we analyzed Mycobacterium tuberculosis strains resistant to ofloxacin (n = 26) and to capreomycin and/or amikacin (n = 48) from Uzbekistan for variations in target genes (gyrA, gyrB, rrs, and tlyA). Strains susceptible to ofloxacin (n = 49) and capreomycin and/or amikacin (n = 39) were included as controls. Mutations in gyrA or gyrB were found in 96% (25/26 strains) of the ofloxacin-resistant strains, while none of the susceptible strains displayed mutations in those two genes. The most common mutation occurred in gyrA at codon 94 (17/26 strains [65.4%]), followed by mutations at codons 90 and 91. Two strains showed a mutation in gyrB, at codons 485 and 543, respectively; both mutations have not been reported previously. The most frequent mutation in strains resistant to both amikacin and capreomycin was A1401G in rrs (34/40 strains [85.0%]). Three strains had mutations in tlyA, of which two (at codons 18 and 118) were associated with resistance to capreomycin alone. Overall, none of the 10 resistant strains (5 amikacin-resistant and capreomycin-susceptible strains) and none of the 39 susceptible control strains had mutations in the genes investigated. Our results clearly demonstrate the potential of sequence analyses of short regions of relatively few target genes for the rapid detection of resistance to second-line drugs among strains isolated from patients undergoing treatment for multidrug-resistant tuberculosis. The mechanisms that confer amikacin resistance in this setting remain unclear.
* Corresponding author. Mailing address. Research Center Borstel, National Reference Center for Mycobacteria, Parkallee 18, 23845 Borstel, Germany. Phone: 49-4537-188274. Fax: 49-4537-188311. E-mail: address: sfeuerriegel{at}fz-borstel.de
Published ahead of print on 26 May 2009.
Supplemental material for this article may be found at http://aac.asm.org/.
Antimicrobial Agents and Chemotherapy, August 2009, p. 3353-3356, Vol. 53, No. 8
0066-4804/09/$08.00+0 doi:10.1128/AAC.00050-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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