Elly,
I have bought this for my daughter but had to do some careful research first because it is not listed as a medicine and can't be sold as such.
She is sensitive to a lot of components so I tracked down the manufacturer and their website is mannose source . Once I went through all content I knew it couldn't do any harm. Worst that could happen was for it not to work. It is just a sugar in the end so it is safe.
I ordered it from just natural stuff here buy d-mannose and it has helped her really well. Now my coleague uses it too and she says it takes indeed a few hours to feel the irritation subside.
Give it a try, if it is not e.coli bothering you it will still be helpful in clearing out other particles in your blood.
Another good article is here.
Good luck!
http://www.saccharides.net/d_mannose.htm