TABLE 2.

Chemiluminescent neuraminidase inhibition assay of A/Texas/12/2007 (H3N2) and plaque-purified clones

Strain designation	Passage levelb	NA mutation	Mean IC50 ±SD (nM)a
			Oseltamivir	Zanamivir	Peramivir	A-315675
A/Texas/12/2007	X/C2	E119V	9.18 ± 1.10	1.09 ± 0.01	ND	ND
A/Texas/12/2007	X/C3	E119(V/I)	8.06 ± 0.41	1.54 ± 0.47	0.51 ± 0.00	1.35 ± 0.15
A/Texas/12/2007 clone 1	X/C4	E119V	5.49 ± 0.03	1.38 ± 0.45	0.43 ± 0.02	1.25 ± 0.03
A/Texas/12/2007 clone 2	X/C4	E119I	33.25 ± 7.01	12.67 ± 5.33	0.90 ± 0.11	4.96 ± 0.47
A/Washington/01/2007 (sensitive control)		None	0.16 ± 0.03	0.76 ± 0.08	0.28 ± 0.02	0.74 ± 0.01

^aAverage IC₅₀ of two independent chemiluminescent NI assays; IC₅₀s of test viruses are compared with those of oseltamivir-sensitive control A/Washington/01/2007 (H3N2) to determine the fold difference in IC₅₀. ND, not done due to insufficient specimen volume.

^bX denotes that the virus isolate was grown in the originating laboratory with an unknown passage number and cell culture, and C2, C3, and C4 denote that the same virus isolate was passaged an additional two, three, or four times, respectively, in MDCK cells at the CDC reference laboratory.