For updated information see Microbiome Prescription
Megasphaera elsdenii NCIMB 41125 is used as a probiotic with cattle
There are 400+ studies on PubMed.
- “We identified links between rosacea and several changes in gut microbiota: reduced abundance of Peptococcaceae family unknown genus, Methanobrevibacter (genus), Slackia (genus), Coprobacillus (genus), Citrobacter (genus), and Desulfovibrio (genus), and increased abundance of Acidaminococcus (genus), Megasphaera (genus), and Lactobacillales order unknown family unknown genus. ” 
- ” Bifidobacterium, Megasphaera, Haemophilus and Streptococcus; and five genera enriched in infants with eczema: Escherichia/Shigella, Veillonella, Faecalibacterium, Lachnospiraceae incertae sedis ” 
- “The levels of Selenomonas ruminantium, Anaerovibrio lipolytica, Ruminobacter amylophilus, Succinivibrio dextrinosolvens and Megasphaera elsdenii were increased by ginkgo extract supplementation, possibly contributing to the higher propionate production.” 
- “Dietary supplementation with B. subtilis resulted in increased (P < 0.05) cecal counts of Megasphaera elsdenii.” 
- Bacillus subtilis