title: Virological surveillance and antiviral resistance of human influenza virus in Argentina, 2005-2008.
abstract: OBJECTIVE
  To describe the virological characteristics of the influenza strains circulating in Argentina in 2005-2008 and to assess the prevalence of antiviral resistance.
  
  
  METHODS
  On the basis of their geographical spread and prevalence, influenza A and B isolates grown in Madin-Darby canine kidney cells were selected after antigenic and genomic characterization to be analyzed for antiviral resistance by enzymatic assay and pyrosequencing. Amantadine susceptibility was evaluated by pyrosequencing for known resistance markers on 45 strains of influenza A. Susceptibility to oseltamivir and zanamivir was evaluated by enzymatic assay of 67 influenza A and 46 influenza B strains, some of which were further analyzed by sequencing the neuraminidase gene.
  
  
  RESULTS
  Resistance to amantadine was observed only on A(H3N2) strains (29/33); all of them carried the mutation S31N in their M2 sequence. Oseltamivir resistance was observed in 12 (34.3%) of the 35 A(H1N1) strains from 2008; all of them carried the mutation H275Y in their neuraminidase sequence. All these viruses remained sensitive to zanamivir.
  
  
  CONCLUSIONS
  This study describes a high incidence of amantadine-resistant influenza A(H3N2) viruses since 2006 and an unprecedented increase in oseltamivir resistance detected only in influenza A(H1N1) viruses isolated in 2008. Influenza A and B viruses were more sensitive to oseltamivir than to zanamivir, and influenza A viruses were more sensitive to both neuraminidase inhibitors than the influenza B viruses. The national data generated and analyzed in this study may help increase knowledge about influenza antiviral drug resistance, which is a problem of global concern.
authors.affiliation: Administración Nacional de Laboratorios e Institutos de Salud "Dr. Carlos G. Malbrán," Instituto Nacional de Enfermedades Infecciosas, Departamento Virología, Buenos Aires, Argentina. aponto@anlis.gov.ar
authors.forename: Andrea
authors.initials: A
authors.lastname: Pontoriero
authors.forename: Elsa
authors.initials: E
authors.lastname: Baumeister
authors.forename: Ana M
authors.initials: AM
authors.lastname: Campos
authors.forename: Vilma L
authors.initials: VL
authors.lastname: Savy
mesh_terms: D000547:Amantadine / Q000494:pharmacology; D000818:Animals; D000998:Antiviral Agents / Q000494:pharmacology*; D001118:Argentina / Q000453:epidemiology; D002460:Cell Line; D004285:Dogs; D024921:Drug Resistance, Multiple, Viral / Q000235:genetics; D024882:Drug Resistance, Viral; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000187:drug effects / Q000235:genetics; D009980:Influenza A virus / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D009981:Influenza B virus / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology / Q000821:virology; D009017:Morbidity / Q000639:trends; D020125:Mutation, Missense; D009439:Neuraminidase / Q000037:antagonists & inhibitors / Q000235:genetics; D053139:Oseltamivir / Q000494:pharmacology; D017354:Point Mutation; D011159:Population Surveillance; D012621:Seasons; D014776:Virus Cultivation; D053243:Zanamivir / Q000494:pharmacology
chemical_list: D000998:Antiviral Agents; D053139:Oseltamivir; D000547:Amantadine; D009439:Neuraminidase; D053243:Zanamivir