Equine Probiotics-What Are They, Where Are We and Where Do We Need To Go?

Probiotics are live microorganisms that when consumed in adequate amounts confer a health benefit to the host. The objective of this review is to critically evaluate the definition of probiotics with reference to their use as supplements in horses, research regarding quality control, and propose areas for future focus. Several studies, performed over a 19-year period, have consistently identified deficiencies when comparing actual contents to label claims. Furthermore, basic information such as expiration dates and storage instructions are often missing from the labels. Finally, the authors will propose several criteria that consumers should consider when choosing probiotics marketed for use in horses.

Microbial Variability of Commercial Equine Probiotics.

Probiotics are defined as live microorganisms that confer a health benefit to the host when administered in adequate amounts, therefore the presence of viable microorganisms is essential. Previous studies reported inconsistencies when comparing contents of probiotics marketed for use in animals with label claims. However, to the author's knowledge the variability of the same product between different lots has yet to be evaluated. The objective of this observational study was to evaluate the content and inter-lot variability of commercial equine probiotic products using culture dependent and independent techniques. Eleven probiotics marketed for use in horses were evaluated for microbial content using culture-dependent and independent techniques. The content was then compared to microorganisms listed and quantities on the label of the probiotic. Statistical analyses were performed using a Kruskal-Wallis test. None of the 11 probiotics met their label claim. Nine of the 11 did not have statistically significant inter-lot variability. Several products lacked microorganisms listed on the label based on both culture and polymerase chain reaction (PCR) analyses.

Effect of an In Vitro Proximal Gastrointestinal Tract on Viability of Commercially Available Equine Probiotics.

Probiotics, by definition, are live micro-organisms and should remain viable when they reach the intended site of action which is typically the cecum and/or colon. In humans, probiotics often need enteric protection to survive transit through the proximal gastrointestinal (GI) tract. Typically, equine probiotics do not advertise enteric protection and to the author's knowledge the viability of equine probiotics after exposure to the proximal GI tract has not been evaluated. The objective of this study was to evaluate the effect of an in vitro simulation of the equine proximal GI tract on probiotic viability. We hypothesized that the simulated proximal GI tract would adversely effect microbial viability and that the adverse effects would be partially ameliorated by increasing the gastric pH to 4. A total of 11 products were evaluated of which six had at least one micro-organism that was adversely effected by exposure to the proximal GI tract and four of which had at least one micro-organism that was adversely affected when the gastric pH was increased to 4.0. Results from this study indicate that some micro-organisms in equine probiotics do not appear to be adversely affected by exposure to the equine proximal GI tract.

Evaluation of commercial probiotics for antimicrobial resistance genes.

The objective of this study was to determine if transferable antimicrobial resistance (AMR) genes are present in commercial animal probiotics. DNA was extracted from 50 probiotics, tested for the presence of bacterial DNA, and analyzed by polymerase chain reaction (PCR) for the presence of 8 transferrable AMR genes, including tetracycline, erythromycin, aminoglycoside, sulfonamide, and trimethoprim. Samples that were positive by PCR were confirmed by genome sequencing. Forty-seven (94%) products contained bacterial DNA. Of these, 97% contained at least 1 AMR gene, and 82% contained 2 or more. These results indicate that further evaluation of the risk for transmission of these AMR genes may be warranted.

Évaluation de probiotiques commerciaux pour des gènes de résistance aux antimicrobiens. L'objectif de la présente étude était de déterminer si des gènes transférables de résistance aux antimicrobiens (RAM) sont présents dans des probiotiques pour animaux du commerce. L'ADN a été extrait de 50 probiotiques, testé pour la présence d'ADN bactérien et analysé par réaction d'amplification en chaîne par la polymérase (PCR) pour la présence de huit gènes RAM transférables, incluant la tétracycline, l'érythromycine, les aminoglycosides, le sulfonamide et le triméthoprime. Les échantillons positifs par PCR ont été confirmés par séquençage du génome. Quarante-sept (94 %) produits contenaient de l'ADN bactérien. Parmi ceux-ci, 97 % contenaient au moins un gène RAM et 82 % en contenaient deux ou plus. Ces résultats indiquent qu'une évaluation plus approfondie du risque de transmission de ces gènes RAM peut être justifiée.(Traduit par Dr Serge Messier).

In Vitro Evaluation of the Effect of Storage at -20°C and Proximal Gastrointestinal Conditions on Viability of Equine Fecal Microbiota Transplant.

Fecal microbiota transplant (FMT), a technique used to restore normal intestinal microbial communities, has been successful in treating humans with Clostridioides difficile colitis. Subsequently, FMT is being used in veterinary patients with suspected intestinal dysbiosis. Unfortunately, little data are available regarding best practices for FMT in horses. The objective of this study was to evaluate the effects of storing manure prepared for equine FMT (MP-FMT) at -20°C for up to 4 weeks and passage through a simulated proximal gastrointestinal (GI) tract on the viability of MP-FMT. The results of this study indicate that storage at -20°C for greater than 1 week and exposure to conditions consistent with the proximal GI tract significantly decreased viability of the microbial population, with gram-negative enteric bacteria most significantly impacted. This preliminary evaluation indicates that further work is necessary to determine best practices to preserve the viability MP-FMT in horses.

Evaluation of commercial veterinary probiotics containing enterococci for transferrable vancomycin resistance genes.

OBJECTIVE: Vancomycin resistant enterococci (VRE) are of significant public health concern. The identification of VRE in livestock and food has increased. The objective of this study was to determine if the transferrable vancomycin resistance genes vanA and vanB were present in probiotics marketed for use in animals that claimed to contain Enterococcus spp. RESULTS: Of the 40 products selected, Enterococcus spp. DNA was successfully extracted from 36 products. Of these 36 products with enterococcal DNA, 2 (6%) had a PCR product consistent with vanA which was confirmed by sequencing. None of the products appeared to contain vanB.