In several of my deep dives, Lactobacillus Kefiri is mentioned as being effective against selective bacteria genus over growths. A reader in Spain found that it is available!
It is not just available, but the strain is given: Lactobacillus Kefiri LKF01 (DSM 32079) LKEF Store URI (In EU)
For this specific strain:
"L. kefiri was recovered in the feces of all volunteers after one month of probiotic administration, while it was detected only in three subjects belonging to the pre-prandial group and in two subjects belonging to the post-prandial group one month after the end of probiotic consumption. After one month of probiotic oral intake we observed a reduction of Bilophila, Butyricicomonas, Flavonifractor, Oscillibacter and Prevotella. Interestingly, after the end of probiotic administration Bacteroides, Barnesiella, Butyricicomonas, Clostridium, Haemophilus, Oscillibacter, Salmonella, Streptococcus, Subdoligranolum, and Veillonella were significantly reduced if compared to baseline samples.
L. kefiri LKF01 showed a strong ability to modulate the gut microbiota composition, leading to a significant reduction of several bacterial genera directly involved in the onset of pro-inflammatory response and gastrointestinal diseases."  [Full Text]
For the species,
- Deleterious Metabolic Effects of High Fructose Intake: The Preventive Effect of Lactobacillus kefiriAdministration .
- " Overall, our results indicate that the administration of probiotics prevents the deleterious effects of fructose-rich diet intake and should therefore be promoted to improve metabolic disorders."
- "Thus, these data suggest that tetracycline resistance in the L. buchneri group (includes L. Keriri) strains is intrinsic, which complies with the requirements defined in the qualified presumption of safety outline." 
- So may be taken with minocycline and other tetracyclines.
This appears to not only reduce many high bacteria genus that CFS patients but also reduces inflammation and appear to take up residency.
If you have any of the high bacteria genus cited above, it is definitely a strong recommendation to discuss with your medical professional.
Q: Could we potentially benefit from eating regular kefir?
A: Alas not -- Kefir is a mixture of many bacteria. They isolate the most effective strain from dozens of different kefirs. A listing of those that could be in Kefir:
Lb. brevis [Possibly now Lb. kefiri]
Lb. casei subsp. casei
Lb. casei subsp. rhamnosus
Lb. paracasei subsp. paracasei
Lb. delbrueckii subsp. bulgaricus
Lb. delbrueckii subsp. lactis
Lb. helveticus subsp. lactis
Lb. kefiranofaciens subsp. kefirgranum
Lb. kefiranofaciens subsp. kefiranofaciens
St. paracitrovorus ^
Lactococcus lactis subsp. lactis
Lc. lactis subsp. lactis biovar. diacetylactis
Lc. lactis subsp. cremoris
Leuconostoc mesenteroides subsp. cremoris
Leuc. mesenteroides subsp. mesenteroides
Leuc. dextranicum ^
Dekkera anomala t/ Brettanomyces anomalus a
Kluyveromyces marxianus t/ Candida kefyr a#
Pichia fermentans t/ C. firmetaria a
Yarrowia lipolytica t/ C. lipolytica a
Debaryomyces hansenii t/ C. famata a#
Deb. [Schwanniomyces] occidentalis
Issatchenkia orientalis t/ C. krusei a
Galactomyces geotrichum t/ Geotrichum candidum a
Kluyveromyces lactis var. lactis #
Saccharomyces cerevisiae #
Sacc. subsp. torulopsis holmii
Sacc. turicensis sp. nov
Torulaspora delbrueckii t
* Zygosaccharomyces rouxii
This is an education post to facilitate discussing this approach with your medical professionals. It is not medical advice for the treatment of CFS. Always consult with your medical professional before doing any changes of diet, supplements or activity. Some items cites may interfere with prescription medicines.
New Probiotic that appears to reduce many of the actual overgrowths seen in IBS and CFS Microbiomes
Blog entry posted by Lassesen, Oct 29, 2017.