Antimicrobial effect of selected yeast fractions on Clostridium perfringens

Saccharomyces cerevisiae derived products are used worldwide to improve the health and performance of animals. Their activity relies in part on their capacity to bind enteropathogenic bacteria, although the in vitro and in vivo mode of action is still not entirely understood. The inhibitory effect exerted by yeast fractions on bacteria seems to be limited to some gram-negative enteropathogens (Salmonella and Escherichia coli), although several in vivo studies report their anti-infectious activity on gram-positive pathogens like clostridia. The effectiveness of four yeast fractions in inhibiting the growth of Clostridium perfringens was quantitatively determined. The most effective fraction, at the minimum effective concentration of 1.25mg/mL, reduced the final cell count by 102 cfu/mL in 24hrs, increased by 3.6hrs the lag phase duration, and reduced by more than 50% the maximum growth rate with respect to the control. All products adsorbed C. perfringens in a dose- and time- dependent manner. The equilibrium adsorption isotherm approach was used to study the inhibition of C. perfringens as a consequence of adsorption, and to determine the maximum adsorption capacity and affinity. The selected yeast fraction sequestered up to 104 cfu of C. perfringens per mg of product. Results were confirmed on other strains, including a NetB toxin producing strain. Cell adsorption onto this product was fast, stable over time, and occurred with high affinity. To the best of our knowledge, this is the first report showing the in vitro efficacy of yeast fractions to inhibit the growth of C. perfringens, and to reduce the culturable cells by an adsorption process.