Development of a new test, GenoType HelicoDR, for molecular detection of antibiotic resistance in Helicobacter pylori
Abstract number: P803
Cambau E., Allerheiligen V., Corbel C., Deforges L., Megraud F.
Objectives: Eradication rate of Helicobacter pylori by standard therapy is decreasing due to an increase in antibiotic resistance. Our aim was to provide a new molecular test to facilitate detection of this resistance.
Methods: A panel of 126 H. pylori strains was studied for phenotypic (MIC) and genotypic resistance to clarithromycin (rrl mutation) and levofloxacin (gyrA mutation). Genotype correlated to phenotype at the rate of 97% for clarithromycin and 100% for levofloxacin. On the basis of the panel test sequencing results and literature data, we developed a genotyping test using the DNA Strip technology. Oligonucleotide probes were wild-type sequences or sequences of the most prevalent mutations. Twenty Helicobacter species other than H. pylori were tested to assess analytical specificity. Clinical strains (n = 64) and H. pylori positive gastric biopsies (n = 109) were tested blindly with the new molecular test GenoType® HelicoDR.
Results: The presence of mutations or the absence of hybridisation with wild-type sequences was predictive in rrl, for clarithromycin resistance in 85 cases (mostly the A2147G mutation), and in gyrA for levofloxacin resistance in 53 cases (mutations at codons 87 or 91). Sensitivity, specificity, and positive and negative predictive values for detecting resistance were 95.5%, 96.5%, 98%, and 96.5% for clarithromycin, respectively, and 87%, 99%, 98% and 93% for levofloxacin, respectively. Concordance score was 0.97 for clarithromycin and 0.95 for levofloxacin. Genotyping showed a mix of genotypes reflecting a co-infection in 31% of strains and 35% of biopsies.
Conclusion: GenoType® HelicoDR is an efficient method to detect mutations predictive of antibiotic resistance in H. pylori when applied to strains or directly to gastric biopsies.
|Session name:||19th European Congress of Clinical Microbiology and Infectious Diseases|
|Location:||Helsinki, Finland, 16 - 19 May 2009|
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