You are opening yourself up to a much greater risk of contamination, and it's not really worth the hassle, and time lost. In operating a cell culture lab, general lab procedures are there to minimise the risk from natural occurring bacterial contaminants, which are precent at low levels, introducing a high level of bacteria into the lab would be inadvisable.
Set up a lab for mammalian cells and a lab for bacteria, and keep them apart. It will save you from a lot of trouble.