I started passing this same stuff back in 2010 when I started doing enemas at home using either dilute apple cider vinegar or just plain water. In 2011 I went to see a Infectious Diseases specialist at a teaching hospital here in Australia and he had the slime/mucus analysed using a scanning electron microscope. The results were negative for candida, so I provided another specimen a few weeks later with the same negative result. I also had specimens sent to different pathology labs earlier on which I assume were analysed using regular light microscopes. These also showed only "bowel mucus", although one stool specimen that I passed naturally after eating lots of sugary foods in an effort to stimulate the growth of candida and have a positive test, showed lots of mucus mixed with red and white blood cells - major indicator of infection or inflammation.
The specialist said one of his areas of interest was biofilms but said that my specimens showed no candida suspended in a biofilm and that it was likely just bowel mucus. The only thing I can think may have happened is that the orally taken coconut oil I used to strip the mucus before I did the enema may have killed/destroyed the candida cells in the biofilm in the process, but who knows. I couldn't think of a way to strip the slime/candida any other way. Maybe I should try doing an enema without taking an antifungal beforehand.
I have to admit that the enemas made me feel a lot better and I think i made more progress with these and the coconut oil than anything else I have done.
What would be helpful if other sufferers like you and Dvorge could also try to have your specimens sent to a lab for electron microscopy. Then at least we can compare and see if we can make sense of all this.
Also, just for the record I also had a gastroscopy and colonoscopy in 2010 and all was normal as well.