Metronidazole- and clarithromycin-resistant Helicobacter pylori in dyspeptic patients in western Sydney as determined by testing multiple isolates from different gastric sites.

Abstract

It is unknown whether antibiotic susceptibility testing of antral isolates alone is representative of Helicobacter pylori susceptibility. We aimed to determine: (i) the prevalence of metronidazole- and clarithromycin-resistant strains in infected dyspeptic patients; and (ii) whether there is consistency in the susceptibility to metronidazole and clarithromycin among isolates cultured from different gastric sites. Antral, body and fundus biopsies were taken from 242 consecutive patients and cultured on blood agar under micro-aerophilic conditions for 5-7 days. Isolates from 66 patients (13 had one, 15 had two and 38 had three isolates) were tested for susceptibility to metronidazole and clarithromycin using previously validated disc diffusion tests. Of the 66 patients, 42 (64%) had strains resistant to metronidazole while four (6.1%) had clarithromycin-resistant strains. The prevalence of metronidazole resistance was not significantly different between men and women (65% vs 60%) or across different age groups. In five (9.4%) of the 53 patients with multiple isolates, discrepant results for metronidazole susceptibility were observed: susceptible antral and body isolates but resistant fundus isolates in two cases and susceptible antral isolates but resistant body and fundus isolates in the others. Clarithromycin susceptibilities were consistent among the isolates cultured from different gastric sites in all patients. It is concluded that metronidazole-resistant strains of H. pylori are common while clarithromycin-resistant strains are rare. Metronidazole susceptibility testing of antral isolates does not appear to be representative of isolates from the body and fundus in a subset of patients.