GREATER THAN 10% OF INFLUENZA A (H1N1) ISOLATES AT CENTRAL PUBLIC HEALTH LABORATORY (CPHL), TORONTO, ONTARIO, CANADA ARE POSITIVE FOR THE NEURAMINIDASE H274Y MUTATION

Session ID:	M10
Author Name:	Eshaghi, A.1, Burton, L1., Low, D.E.1,2,3,, Mazzulli, T.1,2,3, and Drews, S.J. 1,2,3 1Central Public Health Laboratory, Toronto, ON, Canada, 2Mount Sinai Hospital, Toronto, ON, Canada, and 3Department of Pathobiology and Laboratory Medicine, University
Country:	Canada
Conference Session:	Session II

Introduction: The H274Y mutation in the neuraminidase gene of influenza A (H1N1) has been linked to oseltamivir resistance. Recent data suggests that approximately 10% of all H1N1 strains isolated in Canada during the 2007-2008 influenza season are resistant to oseltamivir. This contrasts to previously published levels in other jurisdictions of approximately 1%. The Central Public Health Laboratory (CPHL) of the Ontario Public Health Laboratories acts as a reference virology laboratory for the Canadian province of Ontario and a primary virology testing site for the Greater Toronto Area.

Objective: The purpose of this investigation was to determine the percentage of influenza A (H1N1) isolates at CPHL, Toronto, Ontario, Canada that carry the H274Y mutation in the neuraminidase gene.

Methods: Isolates of influenza A collected from across the province during the 2007-2008 respiratory season at CPHL were screened by RT-PCR for the H1 and /or N1 subtypes. A subset of isolates was also selected for strain analysis by RT-PCR and sequencing of the influenza A neuraminidase gene (ABI 3100, Foster City, CA, USA). Isolate sequences were compared to accessioned sequences of vaccine strains from the 2007-2008 respiratory season. Analysis of strain sequence was carried out using the PHYLIP Phylogeny Inference Package (University of Washington). RT-PCR and sequencing of the region spanning the amino acid position 274 was carried out. Nucleic acid sequences were aligned using CLUSTALX. Translation of nucleic acid sequence to amino acid sequence was carried out by JavaScript DNA Translator 1.1 (Bioinformatics.Net). Query sequences were compared to sequence from isolates with described phenotypic oseltamivir resistance.

Results: A total of 29% (109/378) influenza A (H1N1) isolates were sequenced for strain analysis. All had a gene sequence most like influenza A/Solomon Islands/03/06 (H1N1). A total of 378 isolates of influenza A (H1N1) were sequenced for the H274Y mutation. 14% (53/378) of all sequenced influenza A (H1N1) isolates from the 2007-2008 respiratory season at CPHL carried the H274Y mutation associated with oseltamivir resistance.

Conclusions: Influenza A/Solomon Islands/03/06 (H1N1) was the most predominate strain of influenza A (H1N1) isolated by the CPHL during the 2007-2008 influenza season. Our investigation indicates that 14% of influenza A (H1N1) isolates from Ontario, Canada possess the H274Y mutation associated with oseltamivir resistance. Oseltamivir resistance among influenza A (H1N1) strains is a growing concern within Ontario, Canada and this emerging resistance requires the initiation of a comprehensive surveillance program.