Prevalence of clarithromycin-resistant Helicobacter pylori in patients with chronic tonsillitis by allele-specific Scorpion real-time polymerase chain reaction assay.

Objectives/hypothesis: To investigate the allelic prevalence of resistance to clarithromycin in the DNA of clinical isolates of Helicobacter pylori obtained from biopsy specimens of patients with chronic tonsillitis by Scorpion real-time polymerase chain reaction (PCR).

Study Design: Pathologic specimens of patients with chronic tonsillitis were used for rapid urease test, and blocks of paraffin-embedded tonsillar tissue were used for McMullen staining, rapid urease test, and Scorpion real-time PCR test.

Methods: A total of 103 biopsy samples were obtained from patients with chronic tonsillitis and examined for the presence of clarithromycin resistant H. pylori. Modified McMullen staining and rapid urease test were done on the all the samples. The DNA of specimens was extracted from the pathology blocks, and Scorpion real-time PCR was performed on a final volume of 25 μL.

Results: Of 103 biopsy specimens, 22 samples were identified as infected by H. pylori, of which none were sensitive to clarithromycin. One had the A2143G genotype, and four had the A2142G genotype. Two had a mixed sensitive and the A2143G genotype, and five had a mixed sensitive and A2142G genotype. One strain had a mixed genotype of sensitive, A2143G, and A2142G.

Conclusions: The reported rate of resistance to clarithromycin is of great variation among H. pylori strains isolated from specimens in different countries. Our study showed that the most prevalent genotypes in our H. pylori-positive specimens was A2142G followed by A2143G, which is different from reported results of allele-specific genotyping of H. pylori strains isolated from gastric biopsy and may be a result of cross-resistance to erythromycin and other macrolides.