title: Characterization of oseltamivir-resistant influenza A(H1N1)pdm09 viruses in Taiwan in 2009-2011.
abstract: The early isolated swine-origin influenza A(H1N1)pdm09 viruses were susceptible to oseltamivir; however, there is a concern about whether oseltamivir-resistant influenza A(H1N1)pdm09 viruses will spread worldwide as did the oseltamivir-resistant seasonal influenza A(H1N1) viruses in 2007-2008. In this study, the frequency of oseltamivir resistance in influenza A(H1N1)pdm09 viruses was determined in Taiwan. From May 2009 to April 2011, 1,335 A(H1N1)pdm09-positive cases in Taiwan were tested for the H275Y mutation in the neuraminidase (NA) gene that confers resistance to oseltamivir. Among these, 15 patients (1.1%) were found to be infected with H275Y virus. All the resistant viruses were detected after the patients have received the oseltamivir. The overall monthly ratio of H275Y-harboring viruses ranged between 0% and 2.88%, and the peak was correlated with influenza epidemics. The genetic analysis revealed that the oseltamivir-resistant A(H1N1)pdm09 viruses can emerged from different variants with a great diversity under drug pressure. The ratio of NA/HA activities in different clades of oseltamivir-resistant viruses was reduced compared to those in the wild-type viruses, indicating that the balance of NA/HA in the current oseltamivir-resistant influenza A(H1N1)pdm09 viruses was interfered. It is possible that H275Y-bearing A(H1N1)pdm09 virus has not yet spread globally because it lacks the essential permissive mutations that can compensate for the negative impact on fitness by the H275Y amino acid substitution in NA. Continuous monitoring the evolution patterns of sensitive and resistant viruses is required to respond to possible emergence of resistant viruses with permissive genetic background which enable the wide spread of resistance.
authors.affiliation: Centers for Disease Control, Taipei, Taiwan.
authors.forename: Ji-Rong
authors.initials: JR
authors.lastname: Yang
authors.forename: Yuan-Pin
authors.initials: YP
authors.lastname: Huang
authors.forename: Feng-Yee
authors.initials: FY
authors.lastname: Chang
authors.forename: Li-Ching
authors.initials: LC
authors.lastname: Hsu
authors.forename: Hsiang-Yi
authors.initials: HY
authors.lastname: Huang
authors.forename: Yi-Tsan
authors.initials: YT
authors.lastname: Pan
authors.forename: Yu-Cheng
authors.initials: YC
authors.lastname: Lin
authors.forename: Ho-Sheng
authors.initials: HS
authors.lastname: Wu
authors.forename: Ming-Tsan
authors.initials: MT
authors.lastname: Liu
mesh_terms: D000998:Antiviral Agents / Q000494:pharmacology* / Q000627:therapeutic use; D024882:Drug Resistance, Viral; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000188:drug therapy / Q000821:virology*; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009439:Neuraminidase / Q000235:genetics; D053139:Oseltamivir / Q000494:pharmacology* / Q000627:therapeutic use; D012367:RNA, Viral / Q000235:genetics; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D013624:Taiwan; D014764:Viral Proteins / Q000235:genetics
chemical_list: D000998:Antiviral Agents; D012367:RNA, Viral; D014764:Viral Proteins; D053139:Oseltamivir; C487630:NA protein, influenza A virus; D009439:Neuraminidase