Division I.5.3 Incubation of cell cultures

The inoculated cell cultures shall be incubated at 15 °C for seven to 10 days. If the colour of the cell culture medium changes from red to yellow indicating medium acidification, pH adjustment with sterile bicarbonate solution or equivalent substances shall be performed to ensure cell susceptibility to virus infection.

At least every 6 months or if decreased cell susceptibility is suspected, titration of frozen stocks of VHSV and IHNV shall be performed to verify the susceptibility of the cell cultures to infection. The procedure set out in Section III shall be used, if possible.