Antibiotic resistance in Helicobacter pylori

A A van Zwet and colleagues2van Zwet AA Vandenbrouke-Grauls CMJE Thijs JC van der Wouden EJ Gerrits MM Kusters JG Stable amoxicillin resistance in Helicobacter pylori.Lancet. 1998; 352: 1595Summary Full Text Full Text PDF PubMed Scopus (85) Google Scholar emphasise the importance of susceptibility testing for H pylori in clinical practice. During the past 3 years, we have maintained a database of information from all patients who attended open-access endoscopy in the mid Essex region of the UK. For each patient we recorded: clinical information, histology, and helicobacter serology, culture, and sensitivity. For microbiological confirmation of H pylori infection, two antral biopsy samples were obtained and processed for culture. Specimens were transported in 2 mL of brain heart infusion broth (supplemented with 2–5% yeast extract, 5·0% horse serum) and processed within 2 h of receipt. Biopsy samples were inoculated directly on to Columbia blood agar and selective agar (DENT) plates and incubated for 5 days at 30°C under microaerobic conditions (oxygen 5%, carbon dioxide 5%, hydrogen 2%, nitrogen 88%). Sensitivity tests were done by standard methods on all positive isolates against amoxicillin, clarithromycin, tetracycline, and metronidazole. We examined samples from over 800 patients who presented with symptoms of duodenal ulceration or non-ulcer dyspepsia. The initial resistance rates for amoxicillin and metronidazole during the first year of the study were 0·3% and 33·2%, respectively, all for pretreatment strains. Metronidazole and amoxicillin resistance rates have remained fairly stable, but clarithromycin-resistant strains have increased from 2·3% to 5·7% (table).TableNumber of strains resistant in mid-EssexApril 1995–96(%)April 1996–7(%)April 1997–98(%)Amoxicillin1/308(0·3)2/321(0·6)1/213(0·5)Clarithtromycin7/308(2·3)14/324(4·3)12/211(5·7)Metronidazole103/310(0·3)122/318(0·6)77/211(36·5) Open table in a new tab Previous reports have shown that metronidazole resistance is generally associated with a poor outcome of H pylori eradication therapies that contain metronidazole.2Noach LA Langenberg WI Bertola MA Dankert J Tytgat GN Impact of metronidazole resistance on the eradication of Helicobacter pylori.Scand J Infect Dis. 1994; 26: 321-327Crossref PubMed Scopus (92) Google Scholar, 3Harris A Current regimens for treatment of Helicobacter pylori.Br Med Bull. 1998; 54: 195-205Crossref PubMed Scopus (37) Google Scholar A significant reduction in eradication rates occurs for isolates with dual resistance to metronidazole and clarithromycin and, perhaps more importantly, secondary resistance to clarithromycin was acquired in over 50% of cases of treatment failure.4Xia H Buckley MJ Keane CT O'Morain CA Clarithromycin resistance in Helicobacter pylori: prevalence in untreated dyspeptic patients in stability in vitro.J Antimicrob Chemother. 1996; 37: 473-481Crossref PubMed Scopus (78) Google Scholar, 5Buckley MJ Xia H Hyde DM Keane CT O'Morain CA Metronidazole resistance reduces efficacy of triple therapy and leads to secondary clarithromycin resistance.Dig Dis Sci. 1997; 42: 2111-2115Crossref PubMed Scopus (124) Google Scholar The implication of these findings is that in areas of high prevalence of primary metronidazole resistance, this is an important cause of treatment failure which can potentially lead to the selection of strains with dual resistance. Over the 3 years studied we found that in our subset of metronidazole resistant strains, dual resistance with clarithromycin was 2·9% (3/103), 5·8% (7/121), and 11·7% (9/77). In patients in whom isolates were initially resistant to metronidazole, secondary resistance to clarithromycin was acquired in four of the ten cases of treatment failure. We have now limited the use of serology in our open-access population in favour of management by endoscopic observation, culture, and sensitivity tests. After endoscopy, we wait for culture and sensitivity results before advising general practitioners. This approach greatly increases the sensitivity and specificity of H pylori diagnosis and as such, is an important quality marker. We would also point out that other diagnostic tests available such as urea breath tests and CLO testing do not identify antibiotic resistance, which has become important for future management of H pylori.