Isolation of influenza viruses in MDCK 33016PF cells and clearance of contaminating respiratory viruses

► Multiplex PCR screening of clinical specimens from acute respiratory tract infections. ► Viruses found were influenza, entero/rhino, corona, adeno, boca, PI, RSV, and hMPV. ► After 3 or less passages in MDCK 33016 PF cells, only influenza virus was found. ► Co-infections together with influenza virus were lost within 2-3 MDCK passages. ► MDCK cells represent a barrier for co-infecting viruses in influenza vaccine strains.