engleski

Secondary Helicobacter pylori Resistance to Azithromycin and/or Metronidazole after Treatment Failure

The aim of the study was to evaluate the incidence of secondary Helicobacter pylori resistance to azithromycin and metronidazole after different treatment regimens. Eighty Helicobacter pylori clinical isolates, obtained from gastrics biopsies of 40 patients, before and after unsuccessful eradication were studied. Gastric biopsies were taken before and aproximately 6 weeks after eradication treatment. Minimal inhibitory concentracions (MICs) were determined by agar dilution according to NCCLS documents M7-A4 and M100-S9. Inoculum was adjusted to the turbidity of a 2 McFarland standard. After 3 days of incubation plates were examined for visible growth. Starins were considered resistant with MIC of metronidazole gt then 8 mg/L and azithromycin gt then 2 mg/L. 19 patients received omeprazole 20 mg bid for 10 days + amoxicillin 1000 mg bid for 10 days + metronidazole 500 mg bid for 10 days (A). 16 patients received omeprazole 20 mg bid for 10 days + amoxicillin 1000 mg bid for 10 days + azithromycin 1000 mg once daily for 3 days (B), and 5 patients received omeprazole 20 mg bid for 10 days + metronidazole 500 mg bid for 7 days + azithromycin 1000 mg once daily fro 3 days (C). Results: In pre-treatmenet strains 8/40 (20 per cent) were resistant to azithromycin, and 21/40 (52.2 per cent) were resistant to metronidazole. After treatment 5/32 (15.6 per cent) formerly azithromycin susceptible became resistant, and 8/19 (42.1 per cent) metronidazole susceptible starains to azithromycin, metronidazole or both remained resistant after treatment. Overall pre and post-treatment Helicobacter pylori resistance to azithromycin and metronidazole is shown in figure 1. Conclusion: primary resistance to metronidazole and azithromycin are important prognostic parameters for eradication success. Secondary metronidazole as well as azithromycin resistance is common in unsuccessfully treated cases. Primary resistance to metronidazole is higher than for azithromycin in pre-treatment Helicobacter pylori isolates. The rate of secondary metronidazole resistance is also higher than for azithromycin. Moreover the frequency of azithromycin resistance is higher in starins that are alreaddy resistant to metronidazole. Combined resistance in Helicobacter pylori motivates a constant suceptibility surveilance.

Helicobacter pylori; therapy; resistance; azitromicin

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