The burden of secondary antibiotic resistance in Helicobacter pylori in Auckland, Aotearoa New Zealand.

[AIM] Helicobacter pylori (H. pylori) infection is the principle modifiable risk factor for gastric cancer and a key driver of ethnic disparities in gastric disease within Aotearoa New Zealand. Increasing antibiotic resistance threatens eradication success, yet secondary resistance patterns have not previously been described in New Zealand. This study aimed to describe, for the first time, secondary H. pylori antibiotic resistance rates in New Zealand and identify demographic predictors to inform eradication strategies.

[METHODS] A retrospective review was conducted of H. pylori isolates referred for antibiotic susceptibility testing in Auckland between January 2018 and December 2023. Testing was performed at Middlemore Hospital Laboratory using gradient diffusion minimum inhibitory concentration (MIC) strips for amoxicillin, clarithromycin, metronidazole and tetracycline. Demographic data were obtained from the Auckland TestSafe database and analysed using univariate and multivariable logistic regression.

[RESULTS] Of 3,234 patients tested, 644 (20%) were culture positive. Resistance rates were clarithromycin 68%, metronidazole 68.5%, amoxicillin 2.5% and tetracycline 0%. Male sex was associated with lower odds of metronidazole resistance (p<0.001). Māori and Pacific peoples had lower odds of both metronidazole and clarithromycin resistance compared with Europeans (p<0.05), while Asian ethnicity was associated with higher clarithromycin resistance (p=0.02).

[CONCLUSION] This first-in-New Zealand description of secondary H. pylori resistance shows high rates of clarithromycin and metronidazole resistance. These findings lend support to use of non-clarithromycin-based salvage regimens. Future prospective studies of secondary and also, most importantly, primary resistance data are essential to inform testing and treatment guidelines and improve eradication outcomes.