Novel Molecular Test for H. pylori Evaluated

In times of increasing antibiotic resistance, the need for more rapid resistance screening procedures that replace conventional cultural methods gain importance as H. pylori is a fastidious and slow growing bacterium that can make susceptibility testing from culture a time consuming and challenging task.

Medical microbiologists at the University of Zurich (Switzerland) used a set of 60 H. pylori strains from the culture collection of their Institute of Medical Microbiology. These strains were isolated between 2013 and 2015 from gastric biopsies that were sent to the laboratory for susceptibility testing after clarithromycin (CLR) treatment failure. The strains were intentionally selected based on their phenotypic resistance status to get an evenly distributed number of CLR susceptible (minimum inhibitory concentrations (MIC) ≤0.25 mg/L) and CLR resistant strains (MIC from 0.016 to 256 mg/L).

The scientists compared the CLR susceptibility testing by E-Test and the Lightmix Real-Time Polymerase Chain Reaction assay. A Veriti Thermal Cycler was used for the cycle sequencing program. The team found high concordance (95%) between phenotypical CLR resistance screening by E-Test and the Lightmix RT-PCR. Discrepant results were verified by sequencing of the 23S rRNA gene that always confirmed the results obtained by Lightmix RT-PCR. Furthermore, H. pylori was detected in clinical biopsy and stool specimens by Lightmix RT-PCR that identified the correct H. pylori genotype.

The authors concluded that their data showed that there is a strong association between specific mutations in the 23S rDNA and CLR resistance. The RT-PCR proved to be an exceptional tool for a fast and reliable detection of H. pylori. Furthermore, it allows for CLR resistance screening within a few hours prior to the prescription of an antibiotic therapy and should drastically reduce the cases of treatment failure. The study was published in the January 2018 issue of the journal Diagnostic Microbiology and Infectious Disease.

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