Validation of a Fluorescence In Situ Hybridization Method Using Peptide Nucleic Acid Probes for Detection of Helicobacter pylori Clarithromycin Resistance in Gastric Biopsy Specimens

Cerqueira, Laura, Fernandes, Ricardo M., Ferreira, Rui M., Oleastro, Mónica, Carneiro, Fátima, Brandao, Catarina, Pimentel-Nunes, Pedro, Dinis-Ribeiro, Mário, Figueiredo, Céu, Keevil, Charles W., Vieira, Maria J. and Azevedo, Nuno F. (2013) Validation of a Fluorescence In Situ Hybridization Method Using Peptide Nucleic Acid Probes for Detection of Helicobacter pylori Clarithromycin Resistance in Gastric Biopsy Specimens. Journal of Clinical Microbiology, 51 (6), 1887 - 1893. (doi:10.1128/JCM.00302-13). (PMID:23596234)

Abstract

In here, we evaluated a previously established PNA-FISH method as a new diagnostic test for H. pylori clarithromycin resistance detection in paraffin embedded gastric biopsies. Both a retrospective and a prospective cohort study were conducted to evaluate the specificity and sensitivity of a PNA-FISH method to determine H. pylori clarithromycin resistance. In the retrospective study (n=30 patients), full agreement between PNA-FISH and PCR-sequencing was observed. When compared to the reference method (culture followed by Etest®), specificity and sensitivity of PNA-FISH were 90.9% (95% confidence interval [CI], 57.1-99.5%) and 84.2% (95% CI, 59.5-95.8%), respectively. In the prospective cohort (n=93 patients), 21 cases were positive by culture. For the patients harboring clarithromycin-resistant H. pylori, the method showed a sensitivity of 80.0% (95% CI, 29.9-98.9%) and specificity of 93.8% (95% CI, 67.7-99.7%). These values are likely to be underestimated, as in some discrepant results patients were infected by more than one strain. PNA-FISH appears to be a simple, quick and an accurate method for detecting
H. pylori clarithromycin resistance in paraffin embedded biopsies. It is also the only one of the methods assessed here that allows direct and specific visualization of this microorganism within the biopsies, a characteristic that allowed observing that different H. pylori strains can subsist very closely in the stomach.

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Contributors

Author: Charles W. Keevil

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