Effect of selected yeast fraction on the growth of Clostridium perfringens: quantitative determination of growth inhibition and adsorption capacity

Yeast fractions are used worldwide as promising nutritional solutions to enable the reduction of antibiotics use with respect to the promotion of health and performance in livestock, based on their capacity to bind enteropathogenic bacteria, and for their immunomodulatory activity. The in vitro and in vivo mode of action of YCW yeast fractions, with respect to improving animal performance, is still not entirely understood. The inhibition mechanism exerted by yeast fractions on pathogens seems to be limited to some specific Gram-negative enteropathogens (Salmonella and E. coli), although several in vivo studies report their effect also on Gram positive pathogens like clostridia. The literature lacks in vitro evidences for antimicrobial effect of yeast fractions on C. perfringens strains. The effectiveness of yeast fractions in inhibiting the growth of several C. perfringens strains was quantitatively determined, and one product out of four materials was selected as the best candidate for C. perfringens inhibition. The selected product, at an optimal dosage of 1.25 mg/mL, increased the lag phase duration, and reduced the maximum growth rate and the final cell count in a significant manner with respect to the control. Interestingly, the study proved that the product adsorbed C. perfringens cells in a dose and time dependent manner. Equilibrium isotherms showed that the cell adsorption onto the product was fast, stable over the time, and occurred with high affinity and capacity. The selected product sequestered up to ca. 104 cels of C. perfringens strains per mg, including the NetB toxin producing strain. To the best of our knowledge, this is the first report showing the in vitro efficacy of yeast fraction products to inhibit the growth of C. perfringens, and to reduce the culturable cells by an adsorption process. The in vitro approach proposed herein is as a powerful approach to study the adsorption of aerobic or anaerobic pathogens by eubiotics, thanks to the possibility of modulating culture conditions.