Reference: September 2026 | Issue 9 | Vol 12 | Page 32
New research led by Trinity College Dublin has identified very high rates of Helicobacter pylori (H pylori) antibiotic resistance in the Irish population, with resistance to metronidazole reaching almost 50 per cent.1 The findings have important clinical implications. The study analysed data collected from patients attending Tallaght University Hospital, St James’s Hospital, Letterkenny University Hospital, and Mayo University Hospital for upper endoscopy between January 2018 and June 2023.
Samples from 138 culture-positive patients were included in the study. The mean age of participants was 49.4 ± 15.7 years and 47.1 per cent were female. Just over 83 per cent were treatment-naïve for H pylori. The analyses revealed high levels of resistance.
Rates of resistance to clarithromycin and metronidazole were 41.3 per cent and 49.3 per cent, respectively. Resistance to levofloxacin and amoxicillin reached 19.6 per cent and 17.4 per cent, respectively, while rates for tetracycline and rifampicin resistance were 10.1 per cent and 10.9 per cent.
In the treatment-naïve group, less than a third (28.7%) were susceptible to all six antibiotics tested. Only one sample from the previously treated group was susceptible to all six antimicrobials. Primary resistance to clarithromycin and metronidazole was high in samples from treatment-naïve patients (36.5 per cent and 44.3 per cent, respectively), with dual resistance to clarithromycin and metronidazole observed in 22.6 per cent of isolates. A concerning 13.0 per cent of isolates were multidrug resistant.
When rates were compared between treatment-naïve and previously treated individuals, resistance to clarithromycin significantly increased from 36.5 per cent to 65.2 per cent, and resistance to metronidazole increased from 44.3 per cent to 73.9 per cent.
There was also a significant increase in dual resistance to clarithromycin and amoxicillin (8.7 per cent to 26.1 per cent), clarithromycin and metronidazole (22.6 per cent to 52.2 per cent), and clarithromycin and levofloxacin (7.8 per cent), when rates were compared between samples from treatment-naïve versus previously treated patients.
Multidrug resistance increased from 13.0 per cent in treatment-naïve isolates to 43.5 per cent in isolates from previously treated patients.
Antimicrobial resistance was significantly higher in females compared to males. Clarithromycin resistance rates were 56.9 per cent in females versus 27.4 per cent in males, while rates of resistance to amoxicillin were 24.6 per cent versus 11 per cent, respectively.
Dual resistance to both clarithromycin and amoxicillin reached 23 per cent in females and 4.1 per cent in males, and dual resistance to both clarithromycin and metronidazole was 43.1 per cent versus 13.7 per cent, respectively.
Levofloxacin resistance was over twice as high in older participants (≥65 years) than in those aged less than 65 (38.2 per cent versus 13.5 per cent). Dual resistance to levofloxacin and either clarithromycin or metronidazole was also significantly higher in the ≥60 group. Multidrug resistance was 32.4 per cent versus 13.5 per cent.
Based on the findings, the authors recommend that, since primary clarithromycin resistance decreases the efficacy of standard clarithromycin-amoxicillin-PPI triple therapy by 70 per cent, this combination should not be used as first-line therapy in areas where primary clarithromycin resistance is over 15 per cent.
Based in part on this data, updated Irish consensus guidelines now recommend that clarithromycin triple therapy should only be used in cases where clarithromycin susceptibility has been confirmed. Non-bismuth concomitant therapy (PPI, clarithromycin, metronidazole, and amoxicillin) is not a suitable first-line alternative due to high dual clarithromycin-metronidazole resistance rate.
Hence, bismuth quadruple therapy (PPI, bismuth salt, metronidazole, and tetracycline) is now the recommended first-line treatment. In the absence of antibiotic sensitivity tests (AST), knowledge of a patient’s antibiotic history may prove useful in therapy decision-making, especially in females and older patients.
The authors also advise close monitoring of emerging resistance to amoxicillin, tetracycline, and rifampicin, along with the associated impacts on treatment outcomes.
A recent analysis of more than 900 international samples reported a clarithromycin resistance rate of 22.2 per cent. The rate for metronidazole resistance was 69.2 per cent, while amoxicillin resistance was identified in just 1.2 per cent.2 It is worth noting that Ireland has a proportionately higher use of antimicrobials compared to many other countries in the EU and consumption of β-lactam antibiotics and tetracyclines has been steadily increasing over the years.3
References
- Butler TJ, Molloy S, Douglas A, et al. High levels of Helicobacter pylori antimicrobial resistance in Ireland – a multicentre study. Microorganisms. 2026 Mar 21;14(3):704. doi: 10.3390/microorganisms14030704.
- Mégraud F, Graham DY, Howden CW, et al. Rates of antimicrobial resistance in Helicobacter pylori isolates from clinical trial patients across the US and Europe. Am J Gastroenterol. 2023 Feb 1;118(2):269-275. doi: 10.14309/ajg.0000000000002045.
- Smith SM, Boyle B, Buckley M, et al. The second Irish Helicobacter pylori Working Group consensus for the diagnosis and treatment of Helicobacter pylori infection in adult patients in Ireland. Eur J Gastroenterol Hepatol. 2024;36:1000-1009. doi: 10.1097/MEG.0000000000002796.
