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Helicobacter pylori cag pathogenicity island genotype diversity within the gastric niche of a single host

Mario José Matteo1, Gabriela Granados1, Cecilia Valeria Pérez1

  • 1Departamento de Microbiología, Parasitología e Inmunología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.

Journal of Medical Microbiology
|April 21, 2007
PubMed

Insights

Investigating Helicobacter pylori cag pathogenicity island (PAI) integrity in multiple patient biopsies revealed that nearly a third of patients had varied cagPAI genotypes within the same host, impacting virulence factor analysis.

Area of Science:

  • Microbiology
  • Genetics
  • Infectious Diseases

Background:

  • Helicobacter pylori infection is a major cause of gastritis and peptic ulcers.
  • The cag pathogenicity island (cagPAI) is a key virulence factor associated with severe H. pylori-related diseases.
  • Understanding cagPAI variability within a single host is crucial for correlating infection with clinical outcomes.

Purpose of the Study:

  • To investigate the integrity and variability of the cag pathogenicity island (cagPAI) in Helicobacter pylori isolates from multiple biopsies within individual patients.
  • To determine the prevalence of co-existing cagPAI-positive and cagPAI-negative strains or variants within a single host.
  • To assess the implications of cagPAI heterogeneity on virulence factor expression and clinical presentation.

Main Methods:

  • Analysis of cagPAI integrity using PCR amplification of seven specific loci and the left end of cagII across isolates from multiple biopsies per patient.
  • Confirmation of cagPAI absence via empty-site PCR.
  • Strain delineation using lspA-glmM RFLP and random amplified polymorphic DNA PCR.
  • Recovery and analysis of a total of 218 H. pylori isolates from 40 patients.

Main Results:

  • Mixed infections with distinct H. pylori strains were rare (2/40 patients).
  • A significant proportion of patients (approximately one-third) harbored isolates with intact cagPAI in all niches.
  • Another third had empty-site-positive isolates in all niches, while the remaining third showed disrupted cagPAI in at least one niche.
  • Co-existence of H. pylori variants with different cagPAI genotypes within the same host was observed in approximately one-quarter of patients.
  • Observed variations included diverse deletions, intact vs. partially deleted islands, and intact vs. empty-site-positive variants.

Conclusions:

  • Helicobacter pylori can exhibit significant cagPAI genotype heterogeneity within a single host, affecting virulence potential.
  • The presence of an intact cagPAI in at least one niche was common (50% of patients with genotypic variation).
  • Considering the co-existence of diverse virulence factor genotypes is essential when correlating H. pylori infection with clinical manifestations.

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