Detection of H275Y Mutation of A(H1N1)pdmO9 Viruses Using a Real-time RT-PCR Assay in Mongolia

Abstract

Objectives: Oseltamivir is recommended as a first-line drug for the prophylaxis and treatment of influenza A(H1N1)pdmO9 infection worldwide. However, oseltamivir-resistant influenza A(H1N1)pdmO9 viruses have been identified and are mostly associated with an H275Y substitution in the neuraminidase (NA) gene. Careful and rapid laboratory testing for antiviral resistance surveillance of influenza viruses are important to public health and clinical sectors. The aim of our study was to determine oseltamivir-resistant H275Y mutation in clinical specimens by the real-time reverse transcriptase polymerase chain reaction (rtRT-PCR) assay in Mongolia. Methods: A total of 215 clinical specimens tested positive for the A(H1N1)pdmO9 influenza virus by rtRT-PCR. The specimens were collected between January 2013 and August 2014 from patients who visited influenza surveillance sites. All collected specimens were tested for the presence of the oseltamivir-resistant H275Y mutation by rtRT-PCR and DNA sequencing on the NA gene was performed on four of the clinical samples. Results: For all specimens, the H275 (Ct value = 20.4-34.5) was sensitive to oseltamivir by rtRT-PCR assay for detection of the H275Y mutations in the NA gene. Four questionable clinical samples were sequenced for the full NA gene. The data of these samples are available in GISAID influenza virus database with accession numbers EPI533542, EPI462274, EPI462271 and EPI460844. Conclusion: The A(H1 N1)pdm09 viruses were susceptible to oseltamivir during the study period in Mongolia. The rtRT-PCR assay is useful for detection of the H275Y substitution but other possible mutations in the NA gene of the virus could limit the utility of this technique.