[jfengel]

I wouldn't expect hot water to have a significant effect. In cooking, you need to hit 140F to kill bacteria, which would be extremely unpleasant. It's literally scalding; you can get second and even third degree burns in seconds. Pleasantly-hot shower temperature is in the "danger zone" for food handling, where bacteria grow faster.

Using soap will kill bacteria, and as long as the water is warm enough for the soap to foam up, that's going to do all of the work. Adding more heat will just make things easier on bacteria.