Comparison of Antimicrobial Resistance Testing and Treatment Failure Rates for Helicobacter pylori
T. J. Butler , Deirdre McNamara [1,2], S. Smith [1,3]
 Dept. of Clinical Medicine, School of Medicine, Trinity College Dublin.  Dept. of Gastroenterology, Tallaght University Hospital,  School of Pharmacy and Pharmaceutical Sciences, Trinity College Dublin.
With Helicobacter pylori (HP) resistance on the rise nationally and globally, screening for antibiotic resistance is necessary to ensure populations are receiving appropriate therapies. Unfortunately, antimicrobial susceptibility testing (AST) has poor yields which are complicated by the ever increasing usage of proton pump inhibitors.
To compare the antimicrobial resistance rates by AST to the observed treatment failure rates via urea breath testing (UBT).
All patients referred for their first post eradication urea breath test, having received clarithromycin based triple therapy between 2020-2022 were identified. A positive UBT, delta >4 was considered a marker of clinical treatment failure. Following ethical approval and informed consent, adults were prospectively recruited for AST between February 2020 and August 2022. During routine gastroscopy subjects had 2 additional biopsies (1 antrum and 1 corpus) taken for AST.
In all 482 patients were identified following UBT with the overall clarithromycin treatment failure rate of 25.5%. 250 patients were recruited following gastroscopy for AST, with 29 (11.6%) culture positive for HP and 96 (38.4%) reporting PPI usage. Of the 29 HP strains tested 12 (41.4%) were resistant to clarithromycin as per EUCAST guidelines. Results highlight the significant difference between culture-based resistance rate (41.4%) and treatment failure rates (25.5%) likely owing to the low yield on culture.
Current observed treatment failure rates do not correspond well with culture based methods for antimicrobial resistance, with high rates of PPI usage likely affecting culture success rates.