About your antigen, if you were making polyclonal antibodies the purity would be a problem. Technically, by making monoclonal antibodies you can still get the one you want. But I do envision some problems. Obviously your search for the MAb you want will be made more difficult due to the 20% non-antigen directed Abs. The major problem will be with the search itself. I am not sure how you will find your specific MAbs if you don't at least have pure epitope to facilitate your search. I would suggest that after you do the fusion, subtract the hybridoma cells that are producing MAb against the bacteria as a first screen by using pure bacteria without your antigen. This will help speed things in your search.