Helicobacter pylori pathogenicity and primary antimicrobial resistance in Northern Spain

Helicobacter pylori infection is associated with chronic gastritis, ulcers and gastric cancer. Antimicrobial resistance has increased worldwide affecting the efficacy of current treatments. Most guidelines recommend implementation of regional surveillance of primary antibiotic resistance of H pylori. Only a fraction of individuals infected with H pylori develop gastric diseases which are related to virulence factors of the bacteria. The aims of the study were to determine the primary antimicrobial resistance rates of H pylori and to know the virulence factors prevalence of strains circulating in Southern Europe.

Susceptibility testing by Etest to clarithromycin, levofloxacin, metronidazole, amoxicillin and tetracycline was performed in 102 isolates (99 naïve patients). The prevalence of virulence factors (cagA, vacA, oipA, babA and dupA) was evaluated in 102 H pylori isolates from patients with mild-disease symptoms and in 22 isolates from patients with severe-disease symptoms.

Primary resistance rates were 12.1% to clarithromycin, 13.1% to levofloxacin, 24.2% to metronidazole and 0% to amoxicillin and tetracycline. Combined resistance to clarithromycin and levofloxacin was 3% and to clarithromycin and metronidazole 4%. Prevalence of virulence factors in the mild- and severe-disease group was 35.3% and 81.8% for cagA, 20.6% and 54.5% for cagA/vacAs1m1, 94.1% and 95.4% for babA2, 78.4% and 100% for oipA and 30.4% and 18.2% for dupA.

Primary antimicrobial resistance rates were under 15% for clarithromycin and levofloxacin. The prevalence of H pylori carrying the virulent genotype cagA/vacAs1m1 was higher than 20% in the mild-disease and 54% in the severe-disease symptom group.