Everyones crap smells, Everyones bowel smells. When you see people who have this condition asking for things that make your bowel movement "not smell" you know they are barking up the wrong tree. EVERYONES BOWEL SMELLS, hell most people when cleaning after a bowel movement only clean the after effects of the bowel movement on the anus not the inside(i certainly didnt!)
Now (from my perspective ofcourse) this makes me go back to my symptoms. Pain, feeling of the back door open, wetness, worst after bowel movement etc means for me that the hemmorhoid is causing my sphincter not to close properly thus causing the smell to seep out from the walls of the rectum. As i previously said the last few weeks for me have been very eye opening, and sphincter closing (puh bad joke but it was worth it).
I think someone like yourself in your situation would be in the same situation ie anal sex. One thing to remember is that people can get penetrated in the anus all day long but as long as it doesnt damage the sphincter muscle then they will be fine.
I really think you shouldnt go down the "bacteria" route because at the end of the day obese people, people with horrible diets,people who cant digest foods and such would certainly be much more aware of this if it were the case.
Another thing to remember talking about people who cant "digest foods" is thats the reason its coming out from you is you cant digest it, if you could then it would be used for some way by your body, you cant so it exits via the rectum. Same in everyone.
Candida as well, i wouldnt go near that diagnosis with a bargepoll. It honestly makes no sense with this.
As i said before i hope everything goes ok for you and you get back on track because none of us need this in our life.
All the best.