Nah, let your dog lick it clean since they have cleaner mouths than us filthy humans. Whenever I'm done eating I just let my dog lick the plate/bowl/whatever clean and then it's good to go back in the cupboard.
If you lick it clean and wipe it with a cloth it's probably fine, but that'd be crossing a line for me. I'd rather put a weeks worth of spooned peanut butter in a bag and skooge it out.
For me, I'm more concerned about getting bacteria into the highly nutritious PB. If you're only eating one spoonful then fine. I wouldn't stick a spoon that's been in my mouth back into the container though. I have done this "meal" though, but I scoop how much I want into a bowl first. Maybe drizzle some honey or something onto it.
Butter knife it onto some crackers. (I prefer Ritz.) The knife never goes into the mouth so I can keep using it. Does make a mess on the counter or table if you don't use a paper towel or plate(or bowl) to catch most of the crumbs. Guess you could eat over the sink...
Substituted a knife for the spoon and caulk for peanut butter. Awful taste, horrible recipe. Do not recommend. Would put zero stars but it won't let me.