title: Conservation of the cytotoxin-associated (cagA) gene of Helicobacter pylori and investigation of association with vacuolating-cytotoxin activity and gastroduodenal disease.
abstract: Polymerase chain reaction (PCR) amplification and DNA hybridization analyses were used to test for the presence of the cytotoxin-associated (cagA) gene in 108 strains of Helicobacter pylori. Fifty-two geographically diverse strains of known vacuolating cytotoxin activity, and 56 recent UK clinical isolates from patients with duodenal ulceration (n = 28) and from healthy individuals who were endoscopically normal (n = 28) were studied. Overall, cagA was detected by PCR in 74 (69%) strains and DNA hybridization provided evidence of gene homologues in a further eight strains. For 96% of the cytotoxin-producing strains and 46% of the non-cytotoxin producing strains, there was a close association either with presence or absence of cagA. At the genomic level, Southern blot DNA hybridization showed that cagA was probably present in a single copy in most of the H. pylori tested, and that HaeIII restriction site variation within and around the gene provided additional markers of diversity for the species. As 40% of the cagA containing strains did not produce an active cytotoxin, and no significant association between cagA presence and DU-disease was observed, we concluded that the presence of the cagA gene in H. pylori could not be used as a single reliable predictor of higher risk patients.
authors.affiliation: National Collection of Type Cultures, Central Public Health Laboratory, London, UK.
authors.forename: R J
authors.initials: RJ
authors.lastname: Owen
authors.forename: A
authors.initials: A
authors.lastname: Hurtado
authors.forename: N
authors.initials: N
authors.lastname: Banatvala
authors.forename: Y
authors.initials: Y
authors.lastname: Abdi
authors.forename: G R
authors.initials: GR
authors.lastname: Davies
authors.forename: R
authors.initials: R
authors.lastname: Feldman
authors.forename: J M
authors.initials: JM
authors.lastname: Hardie
mesh_terms: D000942:Antigens, Bacterial; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D003603:Cytotoxins / Q000633:toxicity*; D004381:Duodenal Ulcer / Q000209:etiology*; D005798:Genes, Bacterial; D016480:Helicobacter pylori / Q000235:genetics* / Q000472:pathogenicity; D006801:Humans; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D016133:Polymerase Chain Reaction
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D003603:Cytotoxins; C080866:cagA protein, Helicobacter pylori