title: Hepatitis B virus genotyping among chronic hepatitis B patients with resistance to treatment with lamivudine in the City of Ribeirão Preto, State of São Paulo.
abstract: BACKGROUND
  Lamivudine is a nucleoside analogue that is used clinically for treating chronic hepatitis B infection. However, the main problem with prolonged use of lamivudine is the development of viral resistance to the treatment. Mutations in the YMDD motif of the hepatitis B virus DNA polymerase gene have been associated with resistance to drug therapy. So far, there have not been many studies in Brazil reporting on genotype-dependent development of resistance to lamivudine. Thus, the aim of the present study was to determine the possible correlation between a certain genotype and increased development of resistance to lamivudine among chronic hepatitis B patients.
  
  
  METHODS
  HBV DNA in samples from 50 patients under lamivudine treatment was amplified by means of conventional PCR. Samples were collected at Hospital das Clínicas, FMRP-USP. The products were then sequenced and phylogenetic analysis was performed.
  
  
  RESULTS
  Phylogenetic analysis revealed that 29 (58%) patients were infected with genotype D, 20 (40%) with genotype A and one (2%) with genotype F. Mutations in the YMDD motif occurred in 20% of the patients with genotype A and 27.6% of the patients with genotype D.
  
  
  CONCLUSIONS
  Despite the small number of samples, our results indicated that mutations in the YMDD motif were 1.38 times more frequent in genotype D than in genotype A.
authors.affiliation: Regional Blood Center of Ribeirão Preto, Ribeirão Preto, SP, Brazil. rodrigohaddad@hemocentro.fmrp.usp.br
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Haddad
authors.forename: Ana de Lourdes Candolo
authors.initials: Ade L
authors.lastname: Martinelli
authors.forename: Sérgio Akira
authors.initials: SA
authors.lastname: Uyemura
authors.forename: Jonny
authors.initials: J
authors.lastname: Yokosawa
mesh_terms: D000998:Antiviral Agents / Q000627:therapeutic use*; D001483:Base Sequence; D004279:DNA, Viral / Q000235:genetics; D024882:Drug Resistance, Viral / Q000235:genetics*; D005838:Genotype; D006515:Hepatitis B virus / Q000187:drug effects / Q000235:genetics*; D019694:Hepatitis B, Chronic / Q000188:drug therapy* / Q000821:virology; D006801:Humans; D019259:Lamivudine / Q000627:therapeutic use*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D010802:Phylogeny
chemical_list: D000998:Antiviral Agents; D004279:DNA, Viral; D019259:Lamivudine