Using antibiotic ointment can create a barrier from the outside air and the inside of your nose which can help prevent the flu virus getting into your body through your nose.
But you can still get the flu through other ways of the flu getting into your body so just using antibiotic ointment in your nose won't prevent you from catching the flu virus.
If you touch your eyes or mouth you can get the flu virus into your body that way.
Always wash your hands a lot more when you or someone has the flu and if possible stay away from other people that have the flu to avoid you catching the flu virus from them.
And always call in sick and stay home from work when you have the flu to keep from spreading the flu virus to other people as well.