Table 1.

NA-mediated binding of Sydney/2014 is conferred by a D151G mutation in NA. RG viruses were generated with D151 and G151 NA and their titres recorded in the presence and absence of 40 nM oseltamivir. The HA titre of Sydney/2014 NA D151 was unchanged, while the HA titre of Sydney/2014 NA G151 was entirely abrogated by oseltamivir. Cell-passaged Sydney/2014 isolate (top) demonstrated an intermediate phenotype with a fourfold reduction in HA titre in the presence of oseltamivir owing to the minor (22 %) NA G151 population, determined by NGS

	Amino acid identity at NA151		Haemagglutination assay titre
A/Sydney/71/2014 virus type	D151	G151	−Oseltamivir	+Oseltamivir
Cell-passaged clinical isolate	78 %	22 %	64	16
NA D151 RG virus	100 %	0 %	8	8
NA G151 RG virus	0 %	100 %	64	0