title: Tetracycline resistance in Chilean clinical isolates of Helicobacter pylori.
abstract: OBJECTIVE
  Since high-level tetracycline resistance in Helicobacter pylori has been associated with a AGA926-928-->TTC substitution in the 16S rRNA genes rrnA/B, the aim of the study was to screen for tetracycline resistance in H. pylori clinical isolates obtained from Santiago, Chile by using a recently reported molecular assay.
  
  
  METHODS
  A PCR-restriction fragment length polymorphism (PCR-RFLP) assay of the conserved 535 bp region of the H. pylori 16S rRNA genes rrnA/B (between nucleotides 710 and 1245) using HinfI was followed by DNA sequencing of the same fragment obtained from tetracycline-resistant H. pylori clinical isolates.
  
  
  RESULTS
  The PCR-RFLP assay revealed that the tetracycline-resistant H. pylori isolates lacked the AGA926-928-->TTC substitution. In contrast, DNA sequencing of the 535 bp PCR fragment from 11 tetracycline-resistant H. pylori Chilean clinical isolates showed an association of low-level tetracycline resistance with 1 bp (A928C) or 2 bp (AG926-927-->GT and/or A926G/A928C) substitutions in both 16S rRNA genes.
  
  
  CONCLUSIONS
  The PCR-RFLP (HinfI) assay alone is unreliable for the detection of tetracycline resistance in Chilean clinical isolates of H. pylori. To that end, it must be complemented by sequencing of the 535 bp PCR fragment.
authors.affiliation: Programa de Biología Celular y Molecular, ICBM, Facultad de Medicina, Universidad de Chile, Avenida Independencia 1027, Casilla 70086, Santiago-7, Chile. htoledo@med.uchile.cl
authors.forename: Héctor
authors.initials: H
authors.lastname: Toledo
authors.forename: Remigio
authors.initials: R
authors.lastname: López-Solís
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002677:Chile; D004269:DNA, Bacterial / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D020459:Genes, rRNA; D016481:Helicobacter Infections / Q000382:microbiology*; D016480:Helicobacter pylori / Q000187:drug effects* / Q000302:isolation & purification; D006801:Humans; D025202:Molecular Diagnostic Techniques / Q000379:methods; D017354:Point Mutation; D016133:Polymerase Chain Reaction / Q000379:methods; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA; D013753:Tetracycline Resistance
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; D011933:Reagent Kits, Diagnostic