In vitro neuraminidase inhibitory activity of four neuraminidase inhibitors against influenza virus isolates in the 2011-2012 season in Japan.
J Infect Chemother 2013;
20:77-80. [PMID:
24560563 DOI:
10.1016/j.jiac.2013.07.002]
[Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 06/12/2013] [Accepted: 07/03/2013] [Indexed: 11/29/2022]
Abstract
The neuraminidase inhibitors oseltamivir phosphate (Tamiflu®), zanamivir (Relenza®), laninamivir octanoate (Inavir®), and peramivir (Rapiacta®) have been available for the treatment of influenza in Japan since 2010. To assess the extent of viral resistance, we measured the 50% inhibitory concentration (IC₅₀) of each drug for influenza virus isolates from the 2011-2012 influenza season. Specimens were obtained from patients prior to treatment. Viral isolation was done using Madine-Darby canine kidney cells, and the type and subtype of influenza A(H1N1)pdm09, A(H3N2), or influenza B were determined by RT-PCR using type- and subtype-specific primers. The IC₅₀ was determined by a neuraminidase inhibition assay using a fluorescent substrate. The lineage of influenza B virus was determined by direct sequencing of the hemagglutinin gene. Influenza A(H3N2) and influenza B viruses were isolated in 283 and 42 patients, respectively, while no influenza A(H1N1)pdm09 virus was isolated. No isolate showed an IC₅₀ value exceeding 50 nM for any of the neuraminidase inhibitors. IC50 values for A(H3N2) were similar between the 2010-2011 and 2011-2012 seasons. In contrast, the IC₅₀ values for influenza B viruses in the 2011-2012 season to the four drugs were significantly lower than those found in the 2010-2011 season. These results indicate that the currently epidemic influenza viruses are susceptible to all four neuraminidase inhibitors, with no trend for IC₅₀ values to increase in Japan at present.
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