Distribution of Anti-viral resistant influenza viruses in Phramongkutklao Hospital

Abstract

Influenza A pandemic 2009 H1N1, influenza A H3N2, and influenza B have all been in circulating in Thailand. The data indicate increasing influenza like illness as reported by the Thai National Influenza Center every week. Adamantane an M2 channel blocker and Neuraminidase inhibitors (NAIs) are two classes of antiviral that are available for medical health care. Influenza A resistance to Adamantane drugs is greater than 99% worldwide leaving NAI agents as the only class which the World Health Organization (WHO) recommends for treatment. Oral Oseltamivir is the most commonly used agent worldwide, but many European countries have found Oseltamivir resistance emerging and spreading around the world. Pyrosequencing is a rapid and high throughput method for screening gene markers associated with antiviral susceptibility whereas, the NAI assay is a tool for monitoring phenotypic antiviral resistant by cell culture. Antiviral resistant influenza virus surveillance reports are limited in Thailand. This study was designed to determine the distribution of antiviral resistant influenza virus in Bangkok, Thailand by comparing the results of pyrosequencing and the NAI assay. All seasonal influenza A samples tested had genetic markers consistent with known resistance markers to Adamantane but were still susceptible to Oseltamivir. Both genotypic and phenotypic results showed that Oseltamivir was effective against all influenza viruses in this study. Although antiviral resistance surveillance of influenza virus in Thailand has found a very low percentage of resistant strains the use of Oseltamivir to treat influenza patients should still be monitored and continued surveillance of influenza for resistance in recommended.