Surveillance for Oseltamivir-resistant influenza pandemic A H1N1 viruses in Guangdong province / 中华检验医学杂志

ABSTRACT

Objective To investigate the susceptibility to oseltamivir of influenza pandemic A (H1N1) 2009 viruses in Guangdong province during 2009,provide valuable information of prescription for clinics,and elucidate the variant trend of the epidemic strain based on phylogenetic analysis.Methods During April to December 2009,clinical specimens were collected from sentinel hospitals covering the whole Guangdong province.Virus isolation was performed by in MDCK cells or embryonated chicken eggs.A fluorescence-based neuraminidase (NA) enzyme inhibition assay was conducted to measure influenza susceptibility.The NAI susceptibility of influenza virus was expressed as the concentration of NAI needed to inhibit the NA enzyme activity by 50％.A subset of 68 viruses were performed NA sequencing for detecting resistant mutations and studying variant trends.Results During surveillance,221 influenza pandemic A ( H1N1 ) viruses were isolated.All strains were sensitive to oseltamivir inhibition assay,with a median IC50 of 0.24 nmol/L (range 0.02 -1.66 nmol/L).No mutation related to resistance was found.Phylogenic analysis illustrated that these NA genes were homology high to 99.5％ - 100.0％ with those from other countries.Conclusions influenza pandemic A (H1N1) 2009 viruses were sensitive to oseltamivir in Guangdong,and useful for prophylaxis and treatment of influenza infection.Little selective pressure was found by phylogenic analysis.Our laboratory will continue to observe antiviral-resistance among circulating influenza viruses.