Detection of clarithromycin-resistant Helicobacter pylori in frozen gastric biopsies from pediatric patients by a commercially available fluorescent in situ hybridization.

Clarithromycin resistance is an important factor of eradication failure. A commercially available fluorescent in situ hybridization (FISH) kit (creaFAST) was used to detect H. pylori infection and the resistance to clarithromycin in frozen biopsies. A total of 33 biopsies, H. pylori culture-positive, obtained from pediatric patients were retrospectively studied. Clarithromycin resistance was compared with MICs detected by E-test from H. pylori clinical isolates. All culture-positive biopsies were positive by FISH. Detection of clarithromycin resistance showed sensitivity of 90%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 86.7% compared with results obtained by E-test. Discrepant results were 2 biopsies, clarithromycin-susceptible by FISH but intermediate by E-test. In conclusion, FISH technology is a rapid, easy-to-implement, and reliable cultivation-independent method for routine application; however, when frozen biopsies are studied, some modification of the recommended procedure should be used to obtain better results.