High metronidazole and clarithromycin resistance of helicobacter Pylori isolated from previously treated and naïve patients

Background: Antimicrobial resistance is the main determinant for Helicobacter pylori treatment failure. Regional antimicrobial susceptibility testing is essential for appropriate antibiotic selection to achieve high eradication rates. Objectives: To assess primary and secondary H. pylori resistance in isolates recovered from Israeli naive and treatment failures. To identify predictors of resistance. Methods: In this retrospective study, in vitro activity of isolated H. pylori in Israel was tested against metronidazole, clarithro-mycin, tetracycline, amoxicillin, and levofloxacin in 128 isolates: 106 from treatment failures and 22 from naive untreated patients. The minimal inhibitory concentration values were determined according to the Etest instructions. Treatment failures previously failed at least one treatment regimen. Results: No resistance to amoxicillin and tetracycline was detected. Resistance to metronidazole and clarithromycin was high in H. pylori isolates both from treated and untreated patients: 68.9%, 68.2% for metronidazole (P = 0.95); 53.8%, 59.1% for clarithromycin (P = 0.64), respectively. Dual resistance to clarithromycin and metronidazole was seen in 45.3% and 50%, respectively (P = 0.68). Resistance to levofloxacin was detected in two (1.9%) isolates from treated patients. Simultaneous resistance to clarithromycin, metronidazole, and levofloxacin was seen in an isolate from a treated patient. Age was the only predictor of resistance to metronidazole and clarithromycin. Conclusion: The resistance rates to both single and dual metronidazole and clarithromycin in isolates recovered from both Israeli naive and treated patients is high. Low resistance renders levofloxacin an attractive option for second or third line treatment. Therapeutic outcome would benefit from susceptibility testing after treatment failure.