title: Conservation of the cag pathogenicity island of Helicobacter pylori: associations with vacuolating cytotoxin allele and IS605 diversity.
abstract: OBJECTIVE
  Specific regions of the cag pathogenicity island (PAI) believed to enhance the virulence of Helicobacter pylori, as well as vacuolating cytotoxin gene alleles and IS605 inserts, were investigated to define diversity within infecting strain populations from patients with peptic ulcer disease and from healthy individuals.
  
  
  METHODS
  The H. pylori studied comprised 67 isolates from 26 subjects and 14 reference strains. Specific polymerase chain reaction assays were used to test for cagA and picB in the cagI region, the virD4 homologue in the cagII region, IS605 in the genome and in the cag PAI, the "empty site" indicating absence of the cag PAI, and different vacA gene alleles.
  
  
  RESULTS
  Most (89%) subjects were infected by H. pylori with a contiguous cag PAI. No intermediate forms were found. IS605 was not detected within the cag PAI of any strain but was present elsewhere in the genomes of strains from 62% of subjects. Twenty individuals were infected with genotypically conserved populations of H. pylori. Six subjects had mixed infections, and in 3 of these cag(+)/cag(-) variants were present.
  
  
  CONCLUSIONS
  The cag PAI-positive H. pylori was a feature of most infected individuals, irrespective of severity of associated disease. Combined genotyping showed that 8 individuals (31%) had mixed infections, which suggests that strain population structure may be an additional contributing factor in disease development.
authors.affiliation: Laboratory of Enteric Pathogens, Central Public Health Laboratory, London, England.
authors.forename: E
authors.initials: E
authors.lastname: Slater
authors.forename: R J
authors.initials: RJ
authors.lastname: Owen
authors.forename: M
authors.initials: M
authors.lastname: Williams
authors.forename: R E
authors.initials: RE
authors.lastname: Pounder
mesh_terms: D000483:Alleles; D000942:Antigens, Bacterial; D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics*; D004251:DNA Transposable Elements / Q000235:genetics; D014644:Genetic Variation; D005838:Genotype; D016481:Helicobacter Infections / Q000382:microbiology; D016480:Helicobacter pylori / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity; D006801:Humans; D010437:Peptic Ulcer / Q000382:microbiology*; D037521:Virulence Factors
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; C103937:PicB protein, Helicobacter pylori; C074689:VacA protein, Helicobacter pylori; D037521:Virulence Factors; C080866:cagA protein, Helicobacter pylori