In Ian Lipkin et al 2017 study, high Anaerostipes Caccae and Eubacterium Hallii was reported (on average). [Index to all posts on Study] in CFS patients WITH IBS. ” butyrate-producing and acetate and lactate-utilising bacterium” [Wikipedia]. PubMed has some 18 citations on A.Caccae. It was discovered in 2002. E. Halli occurs very often in those same articles — so I am doing two strains in one post.
- “Whereas E. hallii and A. caccae strains used both D- and L-lactate, the remaining strains used only the d form.”  –NOTE: E. hallii was also reported high with IBS in Lipkin’s study. These species being high may be because they are well fed due to D-Lactic Acidosis.
- “The potential for metabolic cross-feeding between Bifidobacterium adolescentis and lactate-utilizing, butyrate-producing Firmicute bacteria related to Eubacterium hallii and Anaerostipes caccae was investigated in vitro. E. hallii L2-7 and A. caccae L1-92 failed to grow on starch in pure culture, but in coculture with B. adolescentis L2-32 butyrate was formed, indicating cross-feeding of metabolites to the lactate utilizers. Studies with [(13)C]lactate confirmed carbon flow from lactate, via acetyl coenzyme A, to butyrate both in pure cultures of E. hallii and in cocultures with B. adolescentis. Similar results were obtained in cocultures involving B. adolescentis DSM 20083 with fructo-oligosaccharides as the substrate.” 
- ” The patient was initially treated with vancomycin and piperacillin-tazobactam on admission and with amoxicillin-clavulanate upon discharge. The slow-growing organism was subsequently found to be susceptible to metronidazole and ertapenem.” 
- “Anaerostipes caccae DSM 14662T on oligofructose, the latter strain converted lactate (produced by the former strain[Lactobacillus acidophilus] from oligofructose) into butyrate and gases, but only in the presence of acetate.” 
- ” only A. hadrus and A. caccae demonstrated augmented butyrate production from L-sorbose or xylitol. These findings suggest that L-sorbose and xylitol cause prebiotic stimulation of the growth and metabolic activity of Anaerostipes spp. in the human colon.” 
In general leave these alone — they consume d-lactic which we have in abundance with CFS. They are high because of so much food for them. We want to decrease d-lactic production.
However, eliminating L-sorbose and xylitol from the diet seems warranted.