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Helicobacter pylori (H. pylori) is a gram-negative microaerophilic spiral-shaped bacterium, which is able to colonize the mucus layer of the human stomach and the upper part of the small intestine (duodenum).

More than half of the world’s population is estimated to be infected with H. pylori, but most individuals are asymptomatic. H. pylori infection is usually acquired during childhood although the exact means of acquisition is not always clear. H. pylori is involved in the pathogenesis of atrophic gastritis, gastroduodenal ulcer, gastric cancer and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. At present, several diagnostic assays for H. pylori detection are available and grouped as “invasive” or “noninvasive”. Invasive methods include histology culture and rapid urease testing, which require gastric biopsy specimens obtained by gastroduodenoscopy. Noninvasive approaches include fecal antigen, serologic testing, and urea breath testing among others.

H. pylori infection is typically treated with combinations of 2–3 antibiotics along with a PPI (Proton pump inhibitor), taken concomitantly or sequentially, for periods ranging from 3 to 14 days. American College of Gastroenterology Management of H. pylori guidelines published in 2017 recommends Clarithromycin triple therapy consisting of a PPI, clarithromycin, and amoxicillin or metronidazole for 14 days as the first line of treatment in regions where H. pylori clarithromycin resistance is known to be <15%. Accurate statistical information on the prevalence of clarithromycin resistance in North American population is missing.

The presence of clarithromycin resistance reduces the success of clarithromycin triple therapy by ~50%. Until now, two major mutations A2142G and A2143G have been shown to confer the resistance phenotype in clinical isolates. As for other antibiotic resistances, defined mutations are yet to be identified making molecular methods for detection of these other resistances nonviable. Microbiology methods to culture H. pylori are highly challenging (10% success rate from symptomatic biopsy specimens) and characterizing antibiotic resistance is possible only if the culturing techniques were successful.

At Ascenda Biosciences, we have developed and validated a multiplex real-time PCR assay that will assess the presence of Helicobacter pylori in gastric biopsy specimens and determine the clarithromycin resistance genotype. In collaboration with CerTest Biotec in Spain, 300 clinical patient samples were analyzed. Symptomatic and asymptomatic populations were selected and results from Ascenda Biosciences’ molecular test were compared with the data obtained from CerTest Biotec. There was 98% correlation with an analytical specificity of the multiplex assay being 99%.

Determining the clarithromycin resistance associated with Helicobacter pylori will help the physician in determining the most effective antibiotic regimen. The results from the test will be available within 48 hours of the receipt of the biopsy specimens. Ascenda Biosciences also recommends doing the fecal antigen testing two weeks post treatment as a part of Helicobacter pylori eradication confirmation.

Author: Vidhya Narayanan, Ph.D.


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