I'm not sure I would be too confident about whatever bugs have found their way on to grocery store oranges. Just imagine the places they have been before they made it to your beer. I guess it doesn't hurt to try to ferment with them, but I would be sure to test that the pH has dropped as well as the gravity before I put it in my mouth.
On the other hand, just imagine the places they have been before they made it to your beer!
I once attempted to culture yeast off a peach I bought at the grocery store. I have no idea where it was grown but it wasn't local. The beer turned out very mediocre. I saved some of the slurry in a mason jar in the fridge. A couple years later I was pairing down my stock of yeast and discovered the mason jar. I figured I wouldn't brew with it again and dumped it. Only after dumping did I smell the jar and discover how stupid I had been. The smell was a glorious blend of brett funk and lactic acid. I was so disappointed that I had lost that culture. So I definitely think good yeast and LAB can be pulled from grocery store fruit even if the fruit's passengers are international in origin. Probably not coming from ISIS or al Qaeda.