This is a great question and I do recommend taking the difficult step and eliminating antibiotics. New cell culture people should learn from their mistakes and not use antibiotics. This eliminates poor techniques and reinforcing bad habits. I suggest you begin by having multiple vials of cryopreserved cells for each cell type. I would also suggest if everyone is eliminating antibiotics at the same time I would stop culturing cells for a period and do a thorough cleaning of the cell culture labs incubators, biological safety cabinets, water baths, floors etc. Then I would begin thawing each cell type and plate them in media without antibiotics. As the cells grow I would look for low level contaminants popping up. If you find some of your cells are contaminated I would dispose of them and purchase new non-contaminated ones from a vendor. If your cells are a “one of a kind” , then a curing routine is necessary. Of course the goal is good technique and you really learn when using cells grown in antibiotic-free medium.