title: Spread of Influenza A(H1N1) oseltamivir-resistant viruses in Africa in 2008 confirmed by multiple introductions in Senegal.
abstract: BACKGROUND
  Among Influenza neuraminidase inhibitors (NAIs), oseltamivir corresponds to the most widely used agent to treat influenza disease. However since 2001, several cases of resistance to NAIs have been reported for circulating seasonal A(H1N1) Influenza viruses. A direct resistance mechanism may be invoked, involving critical mutations in the viral NA gene that prevent the drug binding to its target. Same phenomenon is reported for adamantanes drugs and mutations in the M2 channel protein gene of Influenza viruses.
  
  
  METHODS
  Reverse-Transcription/Restriction Fragment Length Polymorphism (RT-PCR/RFLP) method, phenotypic testing for oseltamivir resistance, and sequencing of NA, HA and M2 genes were used in this study. Phylogenetic analyses were performed using BioEdit and Mega 5 softwares for alignment of sequences and phylogenetic trees building respectively.
  
  
  RESULTS
  Using a simple RT-PCR/RFLP method, we found that the 86 seasonal A(H1N1) isolates from 2008 bear the oseltamivir resistance-associated mutation (H274Y) in the NA gene. In contrast all isolates isolated in Senegal in 2007 were sensitive to oseltamivir. These results were first confirmed by finding high IC50 values using a phenotypic testing for oseltamivir resistance, and secondly by sequencing the whole NA gene. Regarding M2 gene, no mutation associated to adamantanes resistance was characterized of the isolates.
  
  
  CONCLUSIONS
  The present work provides evidence of circulation of drug-resistant seasonal A(H1N1) viruses during the 2008 influenza season (July to September) in Senegal. The results are in favor of multiple introductions of oseltamivir resistant viruses (ORV) A(H1N1) in Senegal.Phylogenetic analyses of isolates with complete sequences of N1 and HA1 genes showed that they belong to clade 2B and suggest sequential introductions in Africa.
authors: Institut Pasteur de Dakar, Unité de Virologie Médicale, Dakar, Sénégal.
authors: Ndongo
authors: N
authors: Dia
authors: Mbayame N
authors: MN
authors: Niang
authors: Saadiya A
authors: SA
authors: Diadhiou
authors: Déborah G
authors: DG
authors: Goudiaby
authors: Abdourahmane
authors: A
authors: Faye
authors: Davy
authors: D
authors: Kiori
authors: Mady
authors: M
authors: Bâ
authors: Rémy
authors: R
authors: Michel
authors: Ousmane M
authors: OM
authors: Diop
mesh_terms: D000293:Adolescent; D000328:Adult; D000998:Antiviral Agents / Q000494:pharmacology; D002648:Child; D002675:Child, Preschool; D024882:Drug Resistance, Viral; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000145:classification / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology / Q000821:virology*; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D053139:Oseltamivir / Q000494:pharmacology*; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012675:Senegal / Q000453:epidemiology
chemical_list: D000998:Antiviral Agents; C543345:H1N1 virus hemagglutinin; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D053139:Oseltamivir