How do we differentiate between staph epidermidis and saprophyticus?

Both of Staph epidermidis or saprophyticus are catalase + and coagulase – these is why the only way which I can differentiate them from each other is that when I incubate them on agars or petri dishes, I can put a certain antibiotic disc (the disc is about 1 cm in diameter).anitbiogram using disc containing novobiocin, the saprophyticus is resistant to the novobiocin but the epidermidis is sensitive to novobiocin