The concern for Salmonella infections and antibiotic resistance demands the use of safe and effective new interventions in the poultry industry. Yeast postbiotics have been proven to reduce the cecal load of Salmonella in birds, and consequently, the shedding in the environment.

According to the World Health Organization (WHO), unsafe food causes 600 million cases of foodborne diseases and 420,000 deaths each year. Foodborne diseases are caused by eating food contaminated with bacteria, viruses, parasites, or chemical substances, and contamination can occur at any stage of the food production, delivery, and consumption chain. The alarming number of cases responds to the world’s population growth and the increasing demand for food, which puts greater responsibility on food producers to ensure food safety and prevent harmful substances from reaching final consumers. Salmonellosis, for example, is a leading cause of foodborne illness in many countries, with eggs and poultry being primary vehicles of transmission. Eggs are food products that play an important role in supporting the growing global population and provide the final consumer with one of nature’s highest quality sources of protein, vitamins, and minerals that are essential for a healthy diet. Total egg production worldwide rose from 61 million tons in 2008 to 76.8 in 2018; however, the increasing demand for egg production also carries a secondary effect on the transmission of Salmonella as a public health concern.

Zoonotic potential

The Centers for Disease Control and Prevention (CDC) estimates that Salmonella bacteria cause about 1.35 million infections, 26,500 hospitalizations, and 420 deaths in the United States every year. The U.S. Food and Drug Administration (FDA) estimates that 79,000 cases of foodborne illness and 30 deaths each year are caused by eating eggs contaminated with Salmonella. The prevalence of Salmonella represents a major concern in the poultry industry due to the negative impact on the quality of the products destined for human consumption, reduction of production performance, and economic loss for poultry producers. Some prevention and control programs have been developed to protect the health of the birds, ensure the safety of the consumers, strengthen the reliability of the poultry production chain, and prevent vertical and horizontal transmission of multiple pathogens. Such measures include microbiological monitoring, increased biosafety measures, vaccination of flocks, sanitization of feed, and the inclusion of feed additives in the diet.

Previous studies and considerations

Probiotics and postbiotics have gained more attention from researchers and producers due to their efficacy against Salmonella colonization and the increased demand for eggs and poultry free of antibiotics. Recent studies have focused on the use of yeast postbiotics such as Safmannan^®, a selected yeast fraction from Saccharomyces cerevisiae, due to its immunostimulant effect, which has been demonstrated in several animal species, including poultry. This yeast postbiotic is the focus of extensive research as new solution to reduce the use of antibiotics for pathogen control. Research has also shown that supplementing birds with yeast postbiotic may enhance the immune response and reduce the number of pathogens by binding bacteria and creating a complex gut microflora. In a study conducted by Imunova Análises Biológicas, Safmannan^® supplementation led to significant changes in the microflora of broiler birds; microflora was more diverse and beneficial bacteria were significantly increased. Other studies have shown that birds fed with Safmannan^® are more resilient to pathogens and environmental stressors, and exhibit enhanced performance, with improved growth and egg production.

Inhibition of foodborne pathogens

In avian species, the intestines play an essential role not only for nutrients absorption but also as a barrier for pathogens. The caecum, an organ used for fermentation, has an abundant and complex microbiota that has also been reported as a pathogen reservoir for zoonotic pathogens such as Salmonella. Therefore, a recent study at Texas A&M Poultry Research Center evaluated the efficacy of Safmannan^® in reducing the load of Salmonella Typhimurium in ceca of hens. For this study, 90 pullets were divided into two groups in large pens under controlled lighting; one group was supplemented with the Safmannan^® at 500 g/t in the basal diet for three weeks, and the second group was used as control. The birds’ diet was adjusted, following nutritional recommendations, and the lighting was increased daily at 17 weeks of age.

To determine the effect of the Safmannan^® in birds infected with Salmonella Typhimurium, 24 of these pullets were transported to a USDA facility and randomly assigned to one of two groups. Each bird was placed in a cage in a controlled environment and supplemented with either the Safmannan^® supplemented diet or control basal diet. After a two-week acclimatization period, all birds were orally infected with 8.7×10⁹ CFU mL-¹ of Salmonella Typhimurium, and after one week, they were euthanized for sample collection of ceca and ovaries.  Figure 1 shows the levels of Salmonella Typhimurium in the positive ceca as a dot plot. Salmonella Typhimurium counts in the 10 (10/12; 83.3%) ceca positive cultures of the Safmannan^® group were lower than the counts in the 12 (100%) positive cultures from the control group.

Table 1 shows mean ceca counts and after enumeration control sample counts were 4.71 log₁₀ CFU mL^-1, while Safmannan^® sample counts were 3.41 log10 log₁₀ CFU mL^-1 (p = 0.015). Safmannan^® treatment significantly reduced the level of Salmonella Typhimurium in the ceca by 1 log resulting in less Salmonella Typhimurium being shed into the environment. Salmonella spp. can bind to mannose via the type-1 binding fimbriae. Safmannan^® has been shown to bind a variety of gram-negative organisms (Posadas et al., 2017). Reduction of the level of Salmonella in the ceca will reduce the overall load in the environment leading to reduced risk of eggshell contamination and transmission of foodborne illness. Safmannan^® significantly reduced the load of Salmonella Typhimurium in the ceca of the layer type hens. Adding Safmannan^® in layer diets can decrease the cecal load of Salmonella Typhimurium leading to lower contamination of the environment effectively reducing the risk of the zoonotic transmission of Salmonella Typhimurium.

In this study, Safmannan^® reduced the level of Salmonella Typhimurium in the ceca by 1 log. A 1 log reduction of cecal Salmonella is a biologically important result indicating there may be some potential for Safmannan^® to impact levels of Salmonella Typhimurium in the ceca. A reduction of Salmonella in the ceca will reduce the amount shed into the environment reducing the risk of fecal contamination of eggs that enter the food supply. The use of Safmannan^® is gaining relevance in the prevention and control of foodborne pathogens as a strategic food safety intervention in the poultry industry.

References:

Price, P.T., Gaydos, T., Padgett, J.C., Gardner, K. and Bailey, C., 2019. Salmonella colonization of production hens fed a parietal yeast fraction with high levels of mannan and beta-glucan. Int. J. Poult. Sci, 18(9), pp.410-415

Ricke, S.C., Lee, S.I., Kim, S.A., Park, S.H. and Shi, Z., 2020. Prebiotics and the poultry gastrointestinal tract microbiome. Poultry Science, 99(2), pp.670-677.

Stanley, D., Hughes, R.J. and Moore, R.J., 2014. Microbiota of the chicken gastrointestinal tract: influence on health, productivity and disease. Applied microbiology and biotechnology, 98(10), pp.4301-4310