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Volume 19, Number 12—December 2013

Research

Antiviral Susceptibility of Highly Pathogenic Avian Influenza A(H5N1) Viruses Isolated from Poultry, Vietnam, 2009–2011

Ha T. Nguyen, Tung Nguyen, Vasiliy P. Mishin, Katrina Sleeman, Amanda Balish, Joyce Jones, Adrian Creanga, Henju Marjuki, Timothy M. Uyeki, Dang H. Nguyen, Diep T. Nguyen, Hoa T. Do, Alexander I. Klimov, Charles T. Davis, and Larisa V. GubarevaComments to Author 
Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (H.T. Nguyen, V.P. Mishin, K. Sleeman, A. Balish, J. Jones, H. Marjuki, T.M. Uyeki, A.I. Klimov, C.T. Davis, L.V. Gubareva); Battelle Memorial Institute, Atlanta (H.T. Nguyen, A. Creanga); National Center for Veterinary Diagnostics, Hanoi, Vietnam (T. Nguyen, D.H. Nguyen, D.T. Nguyen); Atlanta Research and Education Foundation, Atlanta (J. Jones)

Main Article

Table 1

Clade-specific analysis of drug susceptibility of highly pathogenic avian Influenza A(H5N1) viruses in the neuraminidase inhibition assay*

Neuraminidase inhibitor Clade No. IC50 (nmol/L)
Baseline‡
Mild outliers§
Extreme outliers¶
Min-Max Median Mean±SD† No. Min-Max No. IC50 No. IC50
Oseltamivir
1.1 25 0.04–0.69 0.06 0.07 ± 0.02 23 0.04–0.16 1 0.52 1 0.69
2.3.2.1 70 0.13–527.26 0.41 0.43 ± 0.17 67 0.13–0.87 2 1.72–2.01 1 527.26
2.3.4 28 0.51–11.36 1.62 1.48 ± 0.74 24 0.21–2.79 4 6.76–11.36 0 NA
2.3.4/R**
2
0.48–0.52
NA ‡‡
0.50 ± 0.10

2
0.48–0.52

0
NA

0
NA
Zanamivir
1.1 25 0.13–18.89 0.26 0.28 ± 0.10 23 0.13–0.54 1 1.33 1 18.89
2.3.2.1 70 0.14–1.11 0.32 0.34 ± 0.12 68 0.14–0.68 1 1.11 0 NA
2.3.4 28 0.21–1.71 0.51 0.52 ± 0.18 27 0.21–0.99 1 1.71 0 NA
2.3.4/R
2
0.48–0.62
NA
0.55 ± 0.07

2
0.48–0.62

0
NA

0
NA
Peramivir 1.1 25 0.07–0.31 0.13 0.14 ± 0.03 25 0.07–0.31 0 NA 0 NA
2.3.2.1 70 0.09–91.22 0.20 0.21 ± 0.09 69 0.09–0.47 0 NA 1 91.22
2.3.4 28 0.16–0.52 0.29 0.31 ± 0.10 30 0.16–0.52 0 NA 0 NA
2.3.4/R 2 0.28–0.39 NA 0.33 ± 0.05 2 0.28–0.39 0 NA 0 NA

*IC 50, 50% inhibitory concentration; No., number of viruses analyzed; Min-Max, minimum to maximum of IC50 values; NA, not applicable; IQR, interquartile range.
†Mean and SD of IC50 values after exclusion of outliers.
‡ Viruses with IC50 values <U = Q3+3.0*(IQRIQR= Q3-Q1; Q1 = 25th percentile; Q3= 75th percentile.
§Mild outliers, with IC50 >U but <10-fold difference compared with the median IC50.
¶Extreme outliers, with IC50 >U and ≥10-fold difference compared with the median IC50.
**2.3.4/R,reassortants; the viruses belong to clade 2.3.4 but the neuraminidase genes are grouped with clade 2.3.2.1 (also see Technical Appendix, Table 2).

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