Comparison of fluorescent in situ hybridization and conventional culturingfor detection of Helicobacter pylori in gastric biopsy specimens

In this study, we have investigated 201 gastric biopsy specimens obtained f rom dyspeptic patients for the presence of Helicobacter pylori, By means of fluorescent in situ hybridization (FISH) with rRNA-targeted fluorescence-l abeled oligonucleotide probes specific for H. pylori, this pathogen was det ected in 63 biopsy specimens. By using conventional culturing, H. pylori wa s isolated from 49 of these 63 gastric biopsy specimens. In contrast, FISH failed to identify H. pylori in four samples from which the pathogen was cu ltured, The lowest sensitivity was obtained by using the urease test. H. py lori was detected indirectly by this method in 43 of 67 biopsy specimens, w hich were positive for the pathogen as determined by FISH and/or culturing. All 49 H. pylori isolates that were detected by FISH and culturing underwe nt antimicrobial susceptibility testing for clarithromycin, a macrolide dru g that is a key component in the therapy of peptic ulcer disease caused by this pathogen, Clarithromycin susceptibility testing of cultured isolates w as carried out by the E-test, whereas FISH was used on biopsy specimens to detect clarithromycin-resistant mutant strains. No discrepancies were found between these two methods. Thirty-seven strains were clarithromycin sensit ive, and eight H. pylori isolates were resistant to the macrolide. From ano ther four biopsy specimens, a mixture of clarithromycin-sensitive and -resi stant strains was identified by both methods. Thus, FISH is a reliable tech nique for determining the clarithromycin susceptibility of this pathogen, T aken together, FISH is a more sensitive and rapid technique than culturing for detection of H. pylori in gastric biopsy specimens. However, in the mic robiology routine diagnostic laboratory, the combination of both FISH and c onventional culturing significantly increases the sensitivity in detection of H. pylori.