A two-year survey of the oseltamivir-resistant influenza A(H1N1) virus in Yamagata, Japan and the clinical effectiveness of oseltamivir and zanamivir

Table 2 Inhibition of the enzyme activity of the A(H1N1) isolates in Yamagata in the NA inhibition assay

Viruses	Amino Acid at position 275 in the NA gene	IC₅₀ values in the NA inhibition assay (nM)
		Oseltamivir	Zanamivir
2007-2008 isolates
A/Yamagata/1/2008	Histidine	0.08	0.52
A/Yamagata/66/2008	Tyrosine	50.16	0.45
A/Yamagata/67/2008	Histidine	0.03	0.22
A/Yamagata/68/2008	Tyrosine	39.71	0.55
A/Yamagata/69/2008	Histidine	0.17	0.78
2008-2009 isolates
A/Yamagata/126/2008	Tyrosine	59.04	0.50
A/Yamagata/128/2008	Tyrosine	47.59	0.40

ISSN: 1743-422X