LAUSR

OBJECTIVES Helicobacter pylori infection is responsible for considerable morbidity and mortality worldwide, and eradication rates are falling in many countries, primarily due to clarithromycin and metronidazole resistance. However, there is a paucity of contemporary Australian data, which we sought to address by evaluating local rates of resistance of H. pylori to amoxicillin, clarithromycin, metronidazole, and tetracycline over the past 20 years. DESIGN All gastric biopsy specimens collected at endoscopy to detect H. pylori infection at a single centre underwent routine culture and antibiotic susceptibility testing between 1998-2017. Specimens from 12,842 patients were cultured for H. pylori, of which 1,473 positive cultures were tested for antibiotic susceptibility. RESULTS Antibiotic resistance to clarithromycin increased by 3.7% per year (IRR 1.037, p=0.014) over 20 years, with a corresponding 5.0% annual increase in minimum inhibitory concentration (MIC) (OR 1.050, p<0.001). Since 2010, average clarithromycin resistance has exceeded 20%, with >25% of isolates resistant in the last 2 years of data capture. By contrast, rates of resistance to metronidazole (35.3%), amoxicillin (0.14%) and tetracycline (0.34%) and their MICs have remained stable. Review of a representative sample of these patients (n=120, 8%) revealed that only 5% had documented prior H. pylori eradication therapy. CONCLUSIONS Over the last 20 years there has been a substantial rise in clarithromycin resistance, with stable metronidazole resistance and low rates of resistance to amoxicillin and tetracycline. Current first line H. pylori eradication therapy may fail to achieve adequate eradication rates, and optimal first line therapy in Australia should be revisited. This article is protected by copyright. All rights reserved.