Rapid detection of clarithromycin-resistant Helicobacter pylori in patients with dyspepsia by fluorescent in situ hybridization (FISH) compared with the E-test.

Background: Clarithromycin is the antibiotic of choice for treatment of H.pylori-related dyspepsia, but unfortunately, resistance to clarithromycin is not rare. Detection of resistant strains takes 2 to 4 days by conventional methods. In this report, we applied the FISH technique for rapid detection of H.pylori in biopsies of dyspeptic patients.

Methods: Gastric biopsies from 50 patients suffering from dyspepsia were tested in this study. Part of each biopsy specimen was cultured and the remainder was fixed in liquid nitrogen. After mounting of frozen sections on microscopic slides, they were hybridized with oligonucleotide probes for detection of clarithromycin-resistant H.pylori. The slides were visualized under a fluorescent microscope. Susceptibility of cultured strains of H. pylori to clarithromycin was also determined by the E-test and the results were compared.

Results: Twenty-five of 50 biopsy specimens examined by FISH were positive for H.pylori. FISH showed that 17 strains (68%) were susceptible to clarithromycin and 6 strains (24%) were resistant. Bacteria isolated following culture of 2 biopsy specimens had a mixture of both clarithromycin-susceptible and resistant strains (8%). There was no discrepancy between the E-test and FISH technique for detection of resistant strains of H.pylori.

Conclusion: FISH is a rapid technique for detection of H.pylori in clinical samples. Moreover, strains susceptible to clarithromycin can be detected quickly. Therefore, this method is suitable for determination of susceptibility of H.pylori to clarithromycin, especially when a quick decision is necessary for treating dyspeptic patients.