Assessment of Helicobacter pylori clarithromycin resistance mutations in archival gastric biopsy samples.

Aim: First, to assess the clarithromycin resistance (Cla(R)) rate 1) in patients with persistent Helicobacter pylori (H. pylori) infection after eradication,2) in patients with untreated infection and 3) in patients with successful status post eradication. Second, to evaluate the techniques sequencing and line probe hybridisation INNO-LipA for resolution of uniform and mixed populations in archival gastric biopsy samples.

Methods: The genomic 2142/43 23s rRNA mutations of the 50S ribosomal subunit conferring Cla(R) were detected by PCR-based assays.

Results: A total of 130 patients were investigated. Out of 21 patients of a first series with persistent infection after eradication, 19 (90%; CI (95%): 67-99%) exhibited point mutations at position 2142/43. In the second series of untreated patients, primary resistance was observed in 8 out of 93 patients (9%; CI: 4-16%). In a third series of 16 successfully eradicated patients, pure wild type populations (WT; for loci 2142/43) without any minimal mutated part were found (resistance rate 0%; CI: 0-21%). Further, in all 24 biopsies with uniform mutated and in 8 of 11 biopsies with mixed populations the two molecular biological methods yielded concordant results (100%; CI: 86-100% and 73%; CI: 39-94%, respectively).

Conclusion: In the Baden region of Switzerland, most clarithromycin resistant H. pylori strains harbour mutations at position 2142/43. The primary resistance rate is below 10%. Mixed populations, even with minor mutated part, cannot become successfully eradicated. The two investigated techniques are equally valid for resolution of uniform mutated or mixed H. pylori populations in archival biopsy material.