Can Helicobacter pylori loose its clarithromycin resistance?

Introduction: The most effective antibiotic is Clarithromycin (CLA) in the eradication of Helicobacter pylori (Hp). In cases of unsuccessful eradication, mutation of bacterial rRNA can be detected, which evolves spontaneously giving a selective advantage for the bacteria in cases when unsuitable dose of CLA is administered.

Outcome of resistance might be 1, further administration of any antibiotic will eventually eradicate bacteria 2, there is no eradication at all 3, following CLA administration resistant strain turns to sensitive (conversion). In vitro experiments revealed that the mutant strain is less viable on CLA free culture media than the CLA sensitive strain. On the tenth sequential passage, the sensitive bacterial colonies will dominate the culture media.

Material and methods: In a retrospective study, FISH was performed on gastric biopsy samples. 18 CLA resistant Hp. positive patients were followed with the proper documentation of antibiotic treatment. Mean follow-up time was 21.38 months. The resistant-sensitive conversation time was defined by the elapsed time between the consecutive biopsies taken.

Results: 16 of the 18 cases (89%) remained resistant during the follow-up time (21.81 months) Average number of biopsy samples examined: 2.44. Two cases showed conversion from a resistant strain to sensitive one. Conversion time was 15.5 months. Average number of biopsy samples was: 2.5. Administration of antibiotics turned to be an independent variable and showed a heterogeneous effect.

Discussion: We found only two cases where bacterial strain conversion happened. Resistance remained consistent in non-conversing bacteria despite of the variable antibiotic treatment in 89% of the cases

Conclusion: CLA resistance means from a clinician's perspective that resistance is constant and any treatment modalities should be planned accordingly.