Antimicrobial Susceptibility of Canadian Isolates ofHelicobacter pyloriin Northeastern Ontario

Abstract

BACKGROUND:Helicobacter pyloriplays a significant role in gastritis and ulcers. It is a carcinogen as defined by the WHO, and infection can result in adenocarcinomas and mucosa-associated lymphoid tissue lymphomas. In Canada, rates of antimicrobial resistance are relatively unknown, with very few studies conducted in the past 15 years.OBJECTIVE: To examine rates of resistance in Sudbury, Ontario, compare antimicrobial susceptibility methods and attempt to determine the molecular basis of antibiotic resistance.METHODS: Patients attending scheduled visits at Health Sciences North (Sudbury, Ontario) provided gastric biopsy samples on a volunteer basis. In total, 20H pyloriisolates were collected, and antimicrobial susceptibility testing (on amoxicillin, tetracycline, metronidazole, ciprofloxacin, levofloxacin and clarithromycin) was conducted using disk diffusion and E-test methods. Subsequently, genomic DNA from these isolates was sequenced to detect mutations associated with antimicrobial resistance.RESULTS: Sixty-five percent of the isolates were found to be resistant to at least one of the listed antibiotics according to E-test. Three isolates were found to be resistant to ≥3 of the above-mentioned antibiotics. Notably, 25% of the isolates were found to be resistant to both metronidazole and clarithromycin, two antibiotics that are normally prescribed as part of first-line regimens in the treatment ofH pyloriinfections in Canada and most of the world. Among the resistant strains, the sequences of 23S ribosomal RNA andgyrA, which are linked to clarithromycin and ciprofloxacin/levofloxacin resistance, respectively, revealed the presence of known point mutations associated with antimicrobial resistance.CONCLUSIONS: In general, resistance to metronidazole, ciprofloxacin/levofloxacin and clarithromycin has increased since the studies in the early 2000s. These results suggest that surveillance programs ofH pyloriantibiotic resistance may need to be revisited or improved to prevent antimicrobial therapy failure.