One of the hot topics in medicine currently is information about the microbiome of particular organ systems, particularly the gastrointestinal tract (GIT). The microbiome of the gastrointestinal tract is considered to be very diverse, consisting primarily of anaerobes. Along the way, commensal and pathogenic microorganisms, plus their interactions, will impact the state of the microenvironment. This microenvironment and their by-products (e.g. pH or fatty acid production) interact through the local immune system and enterendocrine signaling ultimately affecting the health status of the GIT.
The normal microbiome in adult dogs and cats is composed mostly of organisms from the phyla Actinobacteria, Bacteroides, Bifidobacteria, Firmicutes, Fusobacteria, and Proteobacteria. It is believed that alterations in normal microbiome composition contribute to acute and chronic enteropathies. There may also be an effect both locally and outside the GIT too, partly as a result of alterations in microbial by-product formation (e.g. increased serum D-lactate concentrations in cats with GIT disease).
Probiotics are comprised of live microorganisms that when consumed in large enough quantities, can lead to a beneficial health effect. How probiotics confer this effect include displacement of pathogenic organisms, production of antimicrobial by-products, improvement in GIT epithelial barrier function, improvement in micronutrient absorption, and modulation of the enteric and innate immune responses. The authors note that even minor alterations to the microbiome can affect whether those benefits are realized.
The actual live microorganism concentration can vary greatly (0.008% to 215% of the labeled concentration) due to stability of the manufacturing process, contamination, long term storage, or just the fastidious nature of some microorganisms. Two products containing the same microorganism strain and concentration could have different effects on the FIT because the manufacturing process differed. Interactions among microorganism species are very important when considering the use of combination probiotic organisms with multiple microorganisms or when assessing synbiotics (a product that combines a prebiotic and probiotic). Prebiotics are defined as substrates for microorganism fermentation that can be tailored to a specific microorganism’s growth needs.
When studying probiotics, one must be aware the in vitro studies have limited clinically applicability because the inability to evaluate their impact on microbial by-product formation, microorganism interaction and other influences. It is noted that studies on the use of probiotics should define the study population clearly (diet, diet history, and microbiome before probiotic administration) and fully describe the probiotic (exact strain, dose, and dosage regimen). Part One. (VT)