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Antimicrobial Agents and Chemotherapy, February 2004, p. 596-601, Vol. 48, No. 2
0066-4804/04/$08.00+0     DOI: 10.1128/AAC.48.2.596-601.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

Multiplex PCR Amplimer Conformation Analysis for Rapid Detection of gyrA Mutations in Fluoroquinolone-Resistant Mycobacterium tuberculosis Clinical Isolates

Augustine F. B. Cheng,1* Wing W. Yew,2 Edward W. C. Chan,1 Miu L. Chin,1 Mamie M. M. Hui,1 and Raphael C. Y. Chan1

Department of Microbiology, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories,1 Tuberculosis and Chest Unit, Grantham Hospital, Aberdeen, Hong Kong, China2

Received 6 July 2003/ Returned for modification 22 August 2003/ Accepted 27 October 2003

A new strategy known as multiplex PCR amplimer conformation was developed for detection of mutation in the gyrA gene of 138 clinical isolates of Mycobacterium tuberculosis. The method generated a single-stranded and heteroduplex DNA banding pattern of multiplex PCR amplimers of the region of interest that was extremely sensitive to specific mutations, thus enabling much more sensitive and reliable mutation analysis compared to the standard single-stranded conformation polymorphism technique. The genetic profiles of the gyrA gene of the 138 isolates as detected by MPAC were confirmed by nucleotide sequencing and were found to correlate strongly with the in vitro susceptibilities of the mutant strains to six fluoroquinolones (ofloxacin, levofloxacin, sparfloxacin, moxifloxacin, gatifloxacin, and sitafloxacin). All 32 isolates that contained gyrA mutations exhibited cross-resistance to the six fluoroquinolones (ofloxacin MIC for 90% of strains > 16 mg/liter), although moxifloxacin, gatifloxacin, and sitafloxacin (MIC for 90% of strains <= 4 mg/liter) were apparently more active than ofloxacin, levofloxacin, and sparfloxacin (MIC for 90% of strains >= 16 mg/liter). All gyrA mutations were clustered in codons 90, 91, and 94, and aspartic acid 94 was most frequently mutated. Twenty-three isolates without gyrA mutations were also found to exhibit reduced susceptibility to ofloxacin (MIC for 90% of strains = 4 mg/liter), but largely remained susceptible to other drugs (MIC for 90% of strains <= 1 mg/liter). Another 83 isolates without mutations were fully susceptible to all six fluoroquinolones (ofloxacin MIC for 90% of strains = 1 mg/liter). In conclusion, high-level phenotypic resistance to fluoroquinolones among M. tuberculosis clinical isolates, which appears to be predominantly due to gyrA mutations, may be readily detected by genotyping techniques such as multiplex PCR amplimer conformation.


* Corresponding author. Mailing address: Department of Microbiology, Chinese University of Hong Kong, Prince of Wales Hospital, 30-32 Ngan Shing St., Shatin, New Territories, Hong Kong SAR, China. Phone: (852) 2632 3333. Fax: (852) 2647 3227. E-mail: a-cheng{at}cuhk.edu.hk.


Antimicrobial Agents and Chemotherapy, February 2004, p. 596-601, Vol. 48, No. 2
0066-4804/04/$08.00+0     DOI: 10.1128/AAC.48.2.596-601.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.




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