Hi Mary,
Although I'm unsure about which beneficial bacteria would be helpful, I just wanted to put something to you. You are probably already aware that the abx you are on are minimally absorbed, so perhaps the improvements you are experiencing are due to the direct affects of the abx, on types of bacteria that might be contributing to your symptoms.
How skeptical is your doc? Would he be interested in investigating this further, if you were to contact him regarding your improvements?
KDM did the study below regarding higher than normal amounts of d-lactic acid producing bacteria found in stool samples of CFS patients.
http://www.cfids-cab.org/rc/Sheedy.pdf
This study is being followed up in Australia, here is a link. Perhaps you could print both links and take them to the doc, and ask if we would be prepared to investigate. It does say in the Nice guildlines that patients with ME can be investigated for bacterial infections.
http://sacfs.asn.au/download/Lactic acid study 2008 - Ethics Application.pdf
If he was interested, he could perform a urinary organic acid test, looking at lactate. This should show a high total reading, which would then suggest a further test for d-lactate. However, the sample must be taken either late afternoon or early evening, as d-lactate has a circadian rythm, and builds up during the day. In urine samples it has been known that morning tests show a negative reading.
D-lactate testing is not normally performed in path labs however, so if the urine test suggested a need for further testing, the doctor would need to look into this, to see where the test could be done. I know Birmingham Hospital to this test, but the blood would need to be centrifuged within a couple of hours of being taken.
High d-lactate causes neurological changes, such as severe lethargy, confusion, disorientation, blurred vision, hyperventilation, headaches, ataxia, slurred speech or difficulty in speaking, nausea, irritability or aggressive behaviour and other symptoms, but a patients would not necessarily have all of these symptoms.
Hope this is useful for you, and however your improvements have come about, I'm delighted that you are feeling better.
Tc,
Glynis x