Thanks for this thread! It helped me decide to try something I was otherwise avoiding.
I tried metronidazole just recently.
First couple of days were no change (I already had all the symptoms they list as side effects: food going straight through me and coming out like vomit, nausea, pain, blah blah blah -to much effort to go back and find the list but yes, had them all).
Then it felt like a cure. I could use my brain again, I've gone a bit drunk with the crazy thrill of being able to use words again, I can understand what people mean when they say things, I wasn't getting those insane heart things where my pulse drops to 30-something bpm for a minute when active, or the thing that means I get freezing cold on a summer day when wearing 3-4 layers of wool and everyone else is in t-shirts (first time I realised this was a real symptom is when I was trying to offer people blankets on such a day), or sweating so hard my clothes were weighed down with sweat.
I took notes, best I stop trying to remember details and just ramble: if anyone wants it I can go find my notes. But really really good. I thought/hoped maybe I was just still weak from a chronic infection that lasted so many months/year but otherwise cured.
But I kept getting overoptimistic and doing too much: not just 20% more than my known limits but 200% or even 500% more. I attended a medical callout, I walked to the top of the hill, I did 3 loads of laundry and vacuumed half the house. Normally it's a good day to get away with a load of laundry (I usually need to do it over a week or so in stages). So the next day my symptoms would return. Not as bad as a crash but bad.
Other than pacing, and avoiding sulphites and preservatives, this is the only thing that has had any real, measurable impact on my function.
[In the end I crashed completely (from the optimistic overdoing). I've been unable to do anything but dress, eat a premade meal, drink, and sit looking at the view (each only for a few minutes before back to bed). When it's bad I feel like my nerves are screaming through from my hands to my stomach and brain. It takes all my considerable strength to simply bear it. As I recovered I started to itch at doing something, so many things, but know that doing anything, including reading (oh for the days when that was what I called rest), sets me back. You all know how important it is to not be in the crash. If I even focused on anything for more than 7minutes my ribs would force me to curl up, my hands shake erratically and I would get so cold, from the tips of my feet and in toward my centre til I couldn't get warm.
Sorry, got lost again, I'm still on the way up and overextending.]
The point is: I think it made a huge difference to my quality of life. But it was not a cure. I still have PEM, I still have to keep to my energy envelope. But now I can think, if I pace myself. I can read this blog in more than 1-2minute intervals. I can do 18 moves of tai chi (really helps with the back, although I can end up soaked in sweat and shaking afterward at the moment). And I'm not always going to the toilet.
The heart stuff and the cold are still happening but I think my limits before they hit are a little wider.
I don't recommend antibiotics. We just don't know enough about that ecology. But there are occasionally times, when the specific antibiotic matches a set of specific pathological parasites and bacteria for my example, when it does help. It's possible.