Distribution of fluoroquinolone MICs in Helicobacter pylori strains from Korean patients

Objectives: The aim of this study was to assess the prevalence rate of primary fluoroquinolone resistance in Helicobacter pylori isolates from Korean patients over the past 16 years. Methods: One hundred and thirty-five strains of H. pylori (34 strains in 1987, 36 in 1994 and 65 in 2003) were isolated from antral gastric mucosal biopsy specimens. The determination of MICs for the H. pylori isolates of ciprofloxacin, levofloxacin and moxifloxacin was examined by using the serial 2-fold agar dilution method. DNA sequences of the gyrA gene in fluoroquinolone-resistant strains were determined. Results: The distribution of fluoroquinolone MICs (ciprofloxacin, levofloxacin and moxifloxacin) shifted to higher concentrations during 1987-2003. All of the levofloxacin- or moxifloxacin-resistant strains were resistant to ciprofloxacin. Sequence analysis in fluoroquinolone-resistant strains showed point mutation of the gyrA gene at A272G and G271A, indicating mutations of the codon Asp-91 in the fluoroquinolone-resistance-determining region of the DNA gyrase. Conclusions: These results suggest that resistance to fluoroquinolones has been increasing in the Korean population and the resistance is most likely mediated through point mutation in gyrA.