i must admit ive done the (to be blunt) hole swapping on many occasions lol and had no infections or any other problems, i dont do the anal to mouth though somebody once made me do that and not only did it made me sick i spent the next few days constantly brushing my teeth and rinsing with mouth wash!

it can occasionally get a little messy but on the whole any 'spare' waste is in the upper colon tract and impossible for it to be reached (if thats part of your question?)
and what many people dont know is that while faeces admittedly isnt too healthy its the waste that doesnt come away and remains in the colon tract (and we all have around 2-6lbs of it) which becomes extremely toxic and basically sends toxic poisons around the whole body, you are just as likely to get infections from water sports for eg to vaginal penetraton and oral.

enemas dont really do an awful lot to clean you up they just basically empty your bowels (even high enemas dont make much difference) only colon cleansing and detox can actually do that.
as long as your externally clean as with any other part of your body even though nowhere no matter how much we bathe what products we use is free from bacteria and germs you should be fine.

lecture over sorry lol