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Antimicrobial Agents and Chemotherapy, March 2001, p. 727-733, Vol. 45, No. 3
Department of Medical Microbiology and
Immunology, University of Alberta, Edmonton, Alberta, Canada
Received 5 September 2000/Returned for modification 15 November
2000/Accepted 7 December 2000
In this study, we systematically examined in vitro frequencies and
spectra of the spontaneous mutations in Helicobacter
pylori that confer resistance to clarithromycin
(Clar), metronidazole (Mtzr), amoxicillin
(Amxr), ciprofloxacin (Cipr), and rifampin
(Rifr). The mutation rate of Rifr
or Cipr determined in a fluctuation assay is
1 × 10
0066-4804/01/$04.00+0 DOI: 10.1128/AAC.45.3.727-733.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Spontaneous Mutations That Confer Antibiotic Resistance in
Helicobacter pylori
8 to 2 × 10
8 per
cell per division. In contrast, the mutation rates of Clar,
Mtzr, and Amxr are much
lower (<10
9). However, Mtzr mutants
could be readily selected in vitro by using the serial passage
method, suggesting that the mutagenic effect and selective effect of a sublethal dose of metronidazole contribute to the rapid
development of Mtzr. Analysis of spontaneous
Rifr, Clar, and Cipr mutants
confirmed previous results indicating that mutations within the
rpoB gene, the 23S rRNA gene, and the
gyrA gene, respectively, are responsible;
also, several new mutant alleles were identified. Mtzr
mutants resulted most frequently, but not always,
from mutations in the rdxA gene. DNA fragments
containing each mutant allele could readily transform susceptible
H. pylori strains to resistance, confirming that
each mutant allele is responsible for the resistance phenotype.
*
Corresponding author. Mailing address: Department of
Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada T6G 2H7. Phone: (780) 492-4777. Fax: (780) 492-7521. E-mail: diane.taylor{at}ualberta.ca.
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