Inhibition of fructan-fermenting equine faecal bacteria andStreptococcus bovisby hops (Humulus lupulusL.)β-acid

Abstract

Aims: The goals of this study were to determine if b-acid from hops (Humulus lupulus L.) could be used to control fructan fermentation by equine hindgut micro-organisms, and to verify the antimicrobial mode of action on Streptococcus bovis, which has been implicated in fructan fermentation, hindgut acidosis and pasture-associated laminitis (PAL) in the horse. Methods and Results: Suspensions of uncultivated equine faecal microorganisms produced fermentation acids when inulin (model fructan) was the substrate, but b-acid (i.e. lupulone) concentrations ≥9 ppm inhibited lactate production and mitigated the decrease in pH. Inulin-fermenting Strep. bovis was isolated from the b-acid-free suspensions after enrichment with inulin. The isolates were sensitive to b-acid, which decreased the viable number of streptococci in faecal suspensions, as well as growth, lactate production and the intracellular potassium of Strep. bovis in pure culture. Conclusions: These results are consistent with the hypothesis that hops b-acid prevented the growth of fructan-fermenting equine faecal bacteria, and that the mechanism of action was dissipation of the intracellular potassium of Strep. bovis. Significance and Impact of the Study: Bacterial hindgut fermentation of grass fructans has been linked to PAL and other metabolic disorders in horses. Hops b-acid is a potential phytochemical intervention to decrease the growth of bacteria responsible for PAL.

Degradation of spent craft brewer's yeast by caprine rumen hyper ammonia‐producing bacteria

“…The hops extract used as a point of comparison in this study did not contain humulone or other a-acids, but it is reasonable to surmise that they would act in a similar fashion. Furthermore, a broad spectrum of antimicrobial activity has been shown against other Gram-positive bacteria from diverse hosts, such as Clostridium perfringens from poultry (Siragusa et al 2008) and Streptococcus bovis from both horses (Harlow et al 2014) and cattle (Flythe and Aiken 2010).…”

Effect of starch source (corn, oats or wheat) and concentration on fermentation by equine faecal microbiota in vitro

“…After arrival at the laboratory, faecal cell suspensions were prepared as previously described (Harlow et al . ). Briefly, faecal material (450 g) was placed in a blender, continuously sparged with N 2 , and mixed (3 min) with 750 ml of cell‐suspension medium.…”

Effects of Hops (<i>Humulus lupulus</i> L.) Beta-Acids on Short Chain Fatty Acid Production from Complex Carbohydrates by Rumen Microbiota

“…The inability of beta-acids to inhibit fermentation of these oligofructose compounds was surprising. A previous study explored the effects of beta-acids on fructan fermentation by equine fecal bacteria [22]. In that case, beta-acids had a dramatic inhibitory effect on SCFA production and pH.…”

“…Streptococcus bovis was the predominant fructanolytic species in horses from which the microorganisms were collected. Streptococcus bovis has a Gram-positive cell envelope, and the susceptibility of multiple isolates to beta-acids has been shown [10] [22]. Streptococcus bovis is a numerically dominant rumen species only under particular conditions [11].…”