Volume 19, Number 12—December 2013
Research
Antiviral Susceptibility of Highly Pathogenic Avian Influenza A(H5N1) Viruses Isolated from Poultry, Vietnam, 2009–2011
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).