Quite true, except it would take more than a few minutes for it to build up. Road kill is far from ideal however; freshly killed (hunted/shot) bunnies, pigeons, crows etc are much better.
Must have had an enormous amount of bacteria when live, then. Bacteria only multiply every 20 minutes (by mitosis), so the numbers would "only" double in that time. That's a very small increase in bacterial terms. The live animal would have to have already been crawling in toxic bacterium to spawn a deadly amount inside 30 minutes (time for one set of mitosis) even under high heat and other condu