Salmonella are a group of bacteria responsible for foodborne illnesses and, as a result, represent a major concern for both public health and the agri-food industry. As eggs and raw poultry are often identified as the source of Salmonella outbreaks, the agri-food industry is trying to raise Salmonella-free swine and poultry. This is particularly challenging to farmers, since chickens colonized with Salmonella do not show overt signs or symptoms of an infection.
There are four common approaches that can be used to reduce the number of Salmonella colonizing chickens: vaccination, competitive exclusion*, feed additives, or antibiotic treatments. However, it should be noted that the use of prophylactic antibiotics is problematic as there are ongoing efforts to decrease the use of antibiotics in response to the global rise of antibiotic resistance in bacterial pathogens. Therefore, in response to this situation researchers are working to develop new feed additives that effectively maintain and promote animal growth, and could eventually replace antibiotics.
Together, Dr Xin Zhao, a CRIPA member and professor at McGill University and his PhD student, Mohsen Pourabedin are trying to identify food additives that effectively impair colonization of the chicken gut by Salmonella.To this end the team tested the effect of using two prebiotics, mannan-oligosaccharide (MOS) and xylo-oligosaccharide (XOS), as feed additives to prevent Salmonella colonization in a total of 150 newly hatched commercial male broiler chickens. They found that both MOS and XOS decreased the inflammatory immune response in young chickens and also altered the composition of the bacterial community found within the pouch-like structures (caecum) that connect the small and large intestine. This change in bacterial community was marked by a decrease in Salmonella enteritidis colonisation within the caecum, with MOS showing the greater effect. It remains to be determined how MOS and XOS work to decrease the number of Salmonella within the intestine. This is an exciting discovery, as MOS and XOS are more effective at decreasing Salmonella levels than treatment with the antibiotic virginiamycin.
In order to develop the best herd management practices, researchers now need to compare the four methods and determine whether they should be combined. This will allow farmers to maintain zootechnical performance while reducing the levels of Salmonella and other bacterial pathogens, such as Campylobacter and Listeria.
*Competitive exclusion is the introduction of intestinal bacteria from mature chickens into newly hatched chicks to prevent the entry of undesirable bacteria into the same environment. The undesirable bacteria cannot colonize the environment because the space is already occupied.
Source : Mannan- and xylooligosaccharides modulate caecal microbiota and expression of inflammatory-related cytokines and reduce caecal Salmonella enteritidis colonisation in young chickens. Mohsen Pourabedin, Qiaoling Chen, MingMing Yang and Xin Zhao. FEMS Microbiology Ecology, 93, 2017, fiw226.