Emergence of H274Y oseltamivir-resistant A(H1N1) influenza viruses in Japan during the 2008-2009 season.
BACKGROUND
A substantial increase in oseltamivir-resistant A(H1N1) influenza viruses was reported in Europe in late 2007.


OBJECTIVE
To monitor the antiviral susceptibility profile of human A(H1N1) influenza viruses in Japan during the 2007-2008 and 2008-2009 seasons.


METHODS
Viruses were obtained from respiratory samples of patients with influenza collected in Japan between December 2007 and April 2008 (n=1046) and between December 2008 and April 2009 (n=1789). Oseltamivir resistance was determined by an H274Y-specific real-time PCR cycling probe assay and a neuraminidase inhibition assay. Amantadine resistance was assessed by sequencing the M2 gene. Sequencing of the hemagglutinin and NA genes was performed to infer phylogenetic relationships between different strains.


RESULTS
Three of 687 (0.4%) A(H1N1) viruses from the 2007-2008 season and 745 of 745 (100%) viruses from the 2008-2009 season carried the NA-H274Y substitution and demonstrated a >300-fold reduction in oseltamivir susceptibility. All oseltamivir-resistant viruses from the 2008-2009 season possessed an A193T substitution in the receptor-binding domain of the hemagglutinin. Amantadine resistance was detected in 431 of 687 (62.7%) and 0 of 745 (0.0%) of the A(H1N1) viruses from the 2007-2008 and 2008-2009 seasons, respectively.


CONCLUSIONS
A dramatic surge in oseltamivir-resistant A(H1N1) viruses possessing the NA-H274Y substitution was detected in Japan during the 2008-2009 season. The emergence of oseltamivir-resistant viruses was facilitated by mutations in the viral genome. Intensified surveillance, including phenotypic assays and sequencing of the hemagglutinin, neuraminidase, and M2 gene would allow monitoring of the spread and evolution of drug-resistant influenza virus variants.
Baranovich
Tatiana
T
Division of Public Health, Department of Infectious Disease Control and International Medicine, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-Dori, Chuoku, Niigata City, Niigata Prefecture 951-8510, Japan. tbar@med.niigata-u.ac.jp
Saito
Reiko
R
Suzuki
Yasushi
Y
Zaraket
Hassan
H
Dapat
Clyde
C
Caperig-Dapat
Isolde
I
Oguma
Taeko
T
Shabana
Iman Ibrahim
II
Saito
Takehiko
T
Suzuki
Hiroshi
H
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000998:Antiviral Agents / Q000494:pharmacology* / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D024882:Drug Resistance, Viral; D005260:Female; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D007251:Influenza, Human / Q000188:drug therapy / Q000453:epidemiology / Q000821:virology*; D007564:Japan; D008297:Male; D008875:Middle Aged; D009439:Neuraminidase / Q000235:genetics / Q000378:metabolism; D053139:Oseltamivir / Q000494:pharmacology* / Q000627:therapeutic use; D010802:Phylogeny; D017354:Point Mutation / Q000235:genetics; D018571:Sentinel Surveillance; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism
D000998:Antiviral Agents; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D014764:Viral Proteins; D053139:Oseltamivir; D009439:Neuraminidase