Updating Primary Antibiotic Resistance in Helicobacter pylori Strains Isolated in Italy.

Background and aims: Bacterial resistance toward the most used antibiotics is increasing in Helicobacter pylori (H. pylori) strains worldwide. The emergence of multidrug resistance significantly affects the efficacy of standard therapy regimens. Therefore, this prospective study has updated the prevalence rates of primary antibiotic resistance in H. pylori strains isolated in routine practice.

Methods: H. pylori isolates obtained from patients consecutively observed in a single center were tested for primary resistance by using the E-test method. The minimum inhibitory concentration (MIC) breakpoints to define resistance to clarithromycin, metronidazole, and levofloxacin were, respectively, greater than 0. 25 mg/L, 8 mg/L, and 1 mg/L, according to updated EUCAST recommendations. The trend of antibiotic prevalence, either single or combined, during 2020-2023 was assessed.

Results: A total of 789 patients meeting inclusion criteria were diagnosed with H. pylori infection, but bacterial strains were overall recovered in 632 (80.1%) cases. At bacterial culture, primary resistance rate was 36.7% for clarithromycin, 32.8% for metronidazole, and 22.1% for levofloxacin, whilst dual clarithromycin-metronidazole resistance rate was detected in 17.4%, and triple resistance in 9%.

Conclusions: Our data found that primary resistance towards both clarithromycin and metronidazole, as well as dual resistance, is substantially stable in Italy whilst the prevalence of levofloxacin resistance seems to be decreasing in our geographic area.