High prevalence of mixed infections by Helicobacter pylori in Hong Kong: metronidazole sensitivity and overall genotype

Background: Diversity in metronidazole susceptibility and genotypes of Heli cobacter pylori have been reported with varying results in different areas. Aims: To investigate the prevalence of multiple strain infection in a sympt omatic Chinese population and to determine the metronidazole susceptibility pattern and genotypic characteristics of these infecting strains. Methods: Gastric biopsies from antrum, body and cardia were taken during up per endoscopy in symptomatic patients referred to our department. Pooled cu ltures and single colony isolates were obtained and tested for metronidazol e susceptibility and random amplified polymorphic DNA (RAPD) fingerprint pa tterns. Results: A total of 461 isolates were successfully cultured from 46 patient s. Fifty-seven per cent of subjects had metronidazole-resistant strains. Am ong them. 77% carried a mixture of sensitive and resistant strains, nan-uni formly distributed in the gastric mucosa. Mixed genotypes were found by RAP D typing in 24% of subjects. These did not correlate with the metronidazole susceptibility/resistance pattern. Conclusion: H. pylori infections with mixed metronidazole sensitive/resista nt strains and mixed genotypes are common in Hong Kong. This makes it prude nt to use bacterial strains from several biopsy sites when testing for trai ts such as drug resistance or virulence in relation to disease.