I understand where this comes from, and your resistance to trying to override your spouse. My partner works in a hospital, too. She tries to keep her 'hospital clothes' separate from everything else, which is probably wise. In her old car, basically nothing else could go in the trunk. Groceries, day-to-day supplies, all went in the back seat, because the trunk was the dirty place. Who am I to argue? I don't see the horrible effects of infection day to day, and I don't go through the procedures they have drilled into them.

Thankfully, it's not like your partner's. We share a car now, and there's just one basket in the trunk for the 'dirty' hospital shoes. She tries to change out of work clothes as soon as getting home and throws them in the laundry. Reasonable precaution, that's fine. She's more squeamish than I am about touching raw meat. But those are all preferences, and it's well under control. I don't think it's OCD related at all, it's just precaution.

In your case, it sounds like your SO has crippling OCD that's being fed/reinforced by rationality. Can you have some kind of intervention where other people who are impacted by this behavior are the loudest voices in the room? It's not good for her, it's not good for you, it's not good for your relationship, and it's not good for your child.