Z Gastroenterol 2005; 43 - 122
DOI: 10.1055/s-2005-869769

Detection of Helicobacter pylori's clarithromycin resistance by FISH. Possibilities and limitations

F Sükösd 1, A Tiszai 2, Z Kiss 2, I Németh 1, L Tiszlavicz 1, J Lonovics 2
  • 1University of Szeged Faculty of General Medicine Department of Pathology
  • 2University of Szeged Faculty of General Medicine First Department of Internal Medicine

Helicobacter pylori (H. pylori) infection is the most common chronic bacterial infection in humans. Estimates indicate that approximately 60% of the world population is colonized by this pathogen. Presence of H. pylori has been reported routineley in gastric biopsy samples since 1994 in our insitute. During this period, there was a decline in the number of H. pylori infected cases. One possible explanation might be a consistent detection and more efficient eradication of H pylori. International data reveal an increasing resistance to clarithromycin the central antibiotic used in treatment.

The number of Hungarian centres currently performing FISH detection increased to five from three since 2003, which was the year of the implementation of FISH technique.

The technique is a breakthrough in the detection of H. pylori's clarithromycin resistance and became a routine test, which can be offered to gastroenterologists.

Aim of the authors is to discuss not only the offered diagnostic use but also the limitations of the technique. Their experiment is based on 857 samples collected from eight geographical regions of Hungary.

A critical approach in diagnosing resistance is mandatory when one interprets the results.

In about 7.3% of H. pylori positive biopsy samples it is not possible to detect signal by FISH. One reason is a prolonged period of fixation as well as difference in the embedding process.

2. Precipitation of a non-specific fluorescent dye should be distinguished from signal of H pylori.

Coccoid forms of H. pylori can pose a diagnostic challenge.

4. In a dense bacterial colony, with intensive signal there might be an overlap leading to false positive result.

In 3.2% of the cases, clarithromycin sensitive and resistant bacteria are present the same time, which might pose difficulty for a clinician.

7. A standard reporting format and proper documentation can be used for auditing the results.

In summary both the clinician and pathologist or other FISH result evaluating person must realise the possibilities given by the technique, but be aware its limitations as well.