For the life of me, I cannot successfully complete the "Prepare the Patient" mini-game no matter how much foam I scrub away. Here's an update:
Prepare the Patient: Swab away germs before they infect Cavity Sam
Use

to swab away the germs that show up.
Quickly keep moving side-to-side, not in a circle, swabbing away the white foam since that’s where the germs grow. The more foam, the more germs there are. You must not have any germs OR white foam on the screen as time expires. If there is, even though the thermometer isn’t completely red, you haven’t won the mini-game.