[Susceptibility of 36 Helicobacter pylori clinical isolates to four first-line antibiotics and virulence factors]

Rev Esp Quimioter. 2006 Mar;19(1):34-8.
[Article in Spanish]

Abstract

Helicobacter pylori possess various virulence factors, including cagA and vacA genes, that are associated with more aggressive symptoms such as bleed-ing ulcer and gastric cancer. Although there are different treatment regimens, there is still a failure rate of up to 20% due to antibiotic resistance, among other causes. In our country resistance to metronidazole and clarithromycin is increasing, especially in children, although they are still susceptible to amoxicillin and tetracycline. In order to determine the susceptibility pattern to these antibiotics 36 H. pylori clinical isolates were studied. MIC was determined by agar diffusion and agar dilution, and vacA and cagA genes were detected by conventional PCR. All isolates were susceptible to amoxicillin and tetracycline. Resistance to metronidazole by diffusion or dilution tests was 35.7% and 36.1%, respectively, and to clarithromycin, 21.4% and 22.3%, respectively. There was one strain that showed intermediate resistance to clarithromycin (MIC 0.38 mg/l), using agar diffusion, and that was included among the resistant strains. Three discrepancies were observed between the diffusion and dilution methods. The vacA s1 allele was detected in 17.2% of the strains, and vacA s2 in 82.8%; 51.7% of the total were cagA+. In conclusion, all strains tested in our study were susceptible to amoxicillin and tetracycline, allowing them to be considered as first-line antibiotics, while clarithromycin and metronidazole maintain a slight increase in their resistance level. The cagA+ strains were detected in expected quantities, while the s1 allele of the vacA gene was detected in lower quantities.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Amoxicillin / pharmacology*
  • Anti-Bacterial Agents / pharmacology*
  • Antigens, Bacterial / genetics
  • Bacterial Proteins / genetics
  • Child
  • Clarithromycin / pharmacology*
  • DNA, Bacterial / genetics
  • DNA, Bacterial / isolation & purification
  • Drug Resistance, Bacterial*
  • Drug Resistance, Multiple, Bacterial
  • Helicobacter Infections / microbiology*
  • Helicobacter pylori / classification
  • Helicobacter pylori / drug effects*
  • Helicobacter pylori / genetics
  • Helicobacter pylori / isolation & purification
  • Helicobacter pylori / pathogenicity
  • Humans
  • Metronidazole / pharmacology*
  • Microbial Sensitivity Tests
  • Species Specificity
  • Tetracycline / pharmacology*
  • Virulence / genetics

Substances

  • Anti-Bacterial Agents
  • Antigens, Bacterial
  • Bacterial Proteins
  • DNA, Bacterial
  • VacA protein, Helicobacter pylori
  • cagA protein, Helicobacter pylori
  • Metronidazole
  • Amoxicillin
  • Tetracycline
  • Clarithromycin