Detection of influenza B viruses with reduced sensitivity to neuraminidase inhibitor in Morocco during 2014/15 season

ABSTRACT

We monitored phenotypic and genotypic susceptibility of influenza viruses circulating in Morocco during 2014-2015 to oseltamivir and zanamivir. Throat and nasal swab specimens were collected from outpatients [with influenza-like illness] and inpatients [with severe acute respiratory illness] and tested for influenza viruses using real-time reverse transcription polymerase chain reaction. Positive samples were inoculated in MDCK cells and virus phenotypic susceptibility to neuraminidase inhibitors [NAIs] was assessed using fluorescent NA inhibition. Of 440 specimens, 135 were positive for influenza B Yamagata-like virus, 38 were A[H1N1] pdm09 and 25 were A[H3N2]. Sixty influenza B viruses isolated from MDCK cells showed no significant resistance to NAIs. However, two of these strains, B/Morocco/176H/2015 and B/Morocco/CP10/2015, showed reduced susceptibility to oseltamivir. The two influenza B viruses with reduced susceptibility to oseltamivir show that ongoing NAI susceptibility surveillance is essential