Volume 15, Number 12—December 2009
Oseltamivir-Resistant Influenza A Pandemic (H1N1) 2009 Virus, Hong Kong, China
|Sample||274H, no. samples positive/no. tested (%)||274Y, no. samples positive/no. tested (%)||IC50 for oseltamivir, nM||IC50 for zanamivir, nM|
|NPA||45/95 (47.37)||50/95 (52.63)||ND||ND|
|MDCK cell culture||2/96 (2.08)||94/96 (97.92)||197.5||0.8|
*50% inhibitory concentrations (IC50s) for oseltamivir and zanamivir were determined by using NA-Star influenza neuraminidase (NA) inhibitor resistance detection kits (Applied Biosystems, Foster City, CA, USA) according to the manufacturer’s instructions. Ratios of 274H and 274Y were evaluated by cloning neuraminidase (NA) gene PCR products from nasopharyngeal aspirate (NPA) samples or MDCK cell–cultured virus into the TA vector (Invitrogen, Carlsbad, CA, USA) and sequencing clones containing the NA gene. ND, not done.