Ciencia y tecnología veterinaria

Abrogation of Salmonella and E. coli O157:H7 in Feedlot Cattle Fed a Proprietary Saccharomyces cerevisiae Fermentation Prototype

Abstract

Kristina M Feye, Kristi L Anderson, Mark F Scott, Darin L Henry, Kristy L Dorton, Brandon E Depenbusch and Steve A Carlson*

Salmonella and E. coli O157:H7 are insidious problems for the beef industry. Asymptomatic fecal shedding of these pathogens contaminates the hide and carcass. Furthermore, Salmonella are unique in their ability to infiltrate lymph nodes leading to the post-harvest contamination of ground beef. These contaminations yield the two most important food safety hazards associated with the consumption of beef. Herein, we report the anti-Salmonella and anti-E. coli O157:H7 effects of a novel Saccharomyces cerevisiae fermentation prototype (PRT; NaturSafeTM) fed to feedlot cattle. Cattle fed PRT were compared to those fed a combination of monensin, tylosin, and a direct-fed microbial- a standard conventional practice in the U.S. beef industry. In this investigator-blinded study, 1,495 feedlot heifers (300-400 kg) were fed PRT (n=747 heifers) or the standard industry diet (PC; n=748 heifers) without PRT for 125-146 days prior to slaughter. At the abattoir, fecal swabs were obtained from 400 animals (n=200/group) and subjected to selective culture for enumerating Salmonella and E. coli O157:H7. Additionally, subiliac lymph nodes were obtained from 400 carcasses for enumeration of Salmonella spp. Salmonella isolated from the feces and lymph nodes were subjected to a virulence assay and some antibiotic susceptibility and Salmonella serovar testing. When compared to cattle that received PC, Salmonella fecal shedding, lymph node infiltration, virulence, and antibiotic resistances were significantly decreased in cattle fed PRT. Additionally, PRT-fed cattle had a lower prevalence of certain Salmonella serovars (Newport, Typhimurium, and Dublin) and shed fewer E. coli O157:H7. The decrease in Salmonella virulence was associated with a decreased expression of hilA, a genetic regulator of Salmonella invasion into eukaryotic cells. This study revealed that a proprietary Saccharomyces cerevisiae fermentation prototype inhibits the shedding, lymph node carriage, downstream virulence, and antibiotic resistance of Salmonella residing in cattle beyond the standard conventional practice that includes monensin, tylosin, and a direct-fed microbial.