Validation of a PNA-FISH method for the detection of Helicobacter pylori

• Author(s): Cerqueira, L. ; Fernandes, RM. ; Ferreira, RM. ; Oleastro, M. ; Carneiro, F. ; Brandão, C. ; Pimentel-Nunes, P. ; Dinis-Ribeiro, M. ; Figueiredo, C. ; Keevil, CW. ; Vieira, MJ. ; Azevedo, NF.
• Date: 2013
• Persistent ID: http://hdl.handle.net/10400.18/1585
• Origin: Repositório Científico do Instituto Nacional de Saúde
• Subject(s): Helicobacter pylori; Peptide Nucleic Acid-fluorescence in Situ Hybridization; Macrolides Resistance; Infecções Gastrointestinais
• Document Type: Article
• Language: English

Description

Here, we evaluated a previously established peptide nucleic acid-fluorescence in situ hybridization (PNA-FISH) method as a new diagnostic test for Helicobacter pylori clarithromycin resistance detection in paraffin-embedded gastric biopsy specimens. Both a retrospective study 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. Compared to the reference method (culture followed by Etest), the specificity and sensitivity of PNA-FISH were 90.9% (95% confidence interval [CI], 57.1% to 99.5%) and 84.2% (95% CI, 59.5% to 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 sensitivity of 80.0% (95% CI, 29.9% to 98.9%) and specificity of 93.8% (95% CI, 67.7% to 99.7%). These values likely represent underestimations, as some of the discrepant results corresponded to patients infected by more than one strain. PNA-FISH appears to be a simple, quick, and accurate method for detecting H. pylori clarithromycin resistance in paraffin-embedded biopsy specimens. It is also the only one of the methods assessed here that allows direct and specific visualization of this microorganism within the biopsy specimens, a characteristic that allowed the observation that cells of different H. pylori strains can subsist in very close proximity in the stomach.