title: Single nucleotide polymorphisms of Helicobacter pylori dupA that lead to premature stop codons.
abstract: BACKGROUND
  The detection of the putative disease-specific Helicobacter pylori marker duodenal ulcer promoting gene A (dupA) is currently based on PCR detection of jhp0917 and jhp0918 that form the gene. However, mutations that lead to premature stop codons that split off the dupA leading to truncated products cannot be evaluated by PCR.
  
  
  METHODS
  We directly sequence the complete dupA of 75 dupA-positive strains of H. pylori isolated from patients with gastritis (n = 26), duodenal ulcer (n = 29), and gastric carcinoma (n = 20), to search for frame-shifting mutations that lead to stop codon.
  
  
  RESULTS
  Thirty-four strains had single nucleotide mutations in dupA that lead to premature stop codon creating smaller products than the predicted 1839 bp product and, for this reason, were considered as dupA-negative. Intact dupA was more frequently observed in strains isolated from duodenal ulcer patients (65.5%) than in patients with gastritis only (46.2%) or with gastric carcinoma (50%). In logistic analysis, the presence of the intact dupA independently associated with duodenal ulcer (OR = 5.06; 95% CI = 1.22-20.96, p = .02).
  
  
  CONCLUSIONS
  We propose the primer walking methodology as a simple technique to sequence the gene. When we considered as dupA-positive only those strains that carry dupA gene without premature stop codons, the gene was associated with duodenal ulcer and, therefore, can be used as a marker for this disease in our population.
authors.affiliation: Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil. sbmoura@icb.ufmg.br
authors.forename: Sílvia B
authors.initials: SB
authors.lastname: Moura
authors.forename: Rafaella F A
authors.initials: RF
authors.lastname: Costa
authors.forename: Charles
authors.initials: C
authors.lastname: Anacleto
authors.forename: Gifone A
authors.initials: GA
authors.lastname: Rocha
authors.forename: Andreia M C
authors.initials: AM
authors.lastname: Rocha
authors.forename: Dulciene M M
authors.initials: DM
authors.lastname: Queiroz
mesh_terms: D000328:Adult; D000368:Aged; D018389:Codon, Nonsense; D004381:Duodenal Ulcer / Q000382:microbiology; D005260:Female; D005756:Gastritis / Q000382:microbiology; D016481:Helicobacter Infections / Q000382:microbiology*; D016480:Helicobacter pylori / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D013274:Stomach Neoplasms / Q000382:microbiology; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D018389:Codon, Nonsense; C528428:DupA protein, Helicobacter pylori; D037521:Virulence Factors