title: Novel genotypes in Helicobacter pylori involving domain V of the 23S rRNA gene.
abstract: BACKGROUND
  Helicobacter pylori is a pathogenic bacterium that infects a half of the human population. In Chile, between 55% and 79% of people are colonized by H. pylori. At present, therapeutic strategies to eradicate the bacterium depend on the knowledge of its resistance to antibiotics. The clarithromycin resistance in H. pylori is associated with point mutations in the 23S rRNA. This study analyzes 23S rRNA gene mutations and minimum inhibitory concentration (MIC) for clarithromycin in H. pylori isolates from patients of the metropolitan region of Chile.
  
  
  METHODS
  H. pylori isolates from 50 dyspeptic patients with no history of clarithromycin exposure were tested for clarithromycin resistance by agar dilution method. Resistant strains were analyzed for mutations in the 23S rRNA gene by polymerase chain reaction-based restriction fragment length polymorphism and sequencing.
  
  
  RESULTS
  Primary resistance was observed in 10 isolates (20%). A single mutation was detected in four of the 10 isolates and two or more mutations in the other six cases. The C2147G transversion and G1939A, T1942C, and A2142G transitions in the peptidyltransferase region of domain V were novel.
  
  
  CONCLUSIONS
  The study shows: 1, novel variants of the H. pylori 23S rRNA gene; and 2, a high prevalence of H. pylori displaying primary clarithromycin resistance with low level of MIC in an urban area of the Metropolitan Region of Chile.
authors.affiliation: Programa de Biologia Celular y Molecular, ICBM, Facultad de Medicina, Universidad de Chile, Avenida Independencia 1027, Casilla 70086, Santiago-7, Chile.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Garrido
authors.forename: Hector
authors.initials: H
authors.lastname: Toledo
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002677:Chile / Q000453:epidemiology; D017291:Clarithromycin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D020459:Genes, rRNA / Q000235:genetics*; D005838:Genotype; D016481:Helicobacter Infections / Q000453:epidemiology* / Q000382:microbiology; D016480:Helicobacter pylori / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012338:RNA, Ribosomal, 23S / Q000737:chemistry / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D000900:Anti-Bacterial Agents; D012338:RNA, Ribosomal, 23S; D017291:Clarithromycin