Probiotics protect against bacterial infection, says study

By Stephen Daniells

- Last updated on GMT

Related tags Probiotic bacteria Probiotic

A newly characterised strain of probiotic bacteria may have
potential to kill Listeria monocytogenes, an often-lethal
pathogen in pregnant women, Irish researchers report.

The research, published in the Proceedings of the National Academy of Sciences​, could see pregnant women and a number of other high-risk groups receiving the probiotic to protect them from potential infection. Lead author Sinead Corr from University College Cork told "Our results clearly demonstrate the ability of certain probiotic bacteria to protect against potentially fatal illnesses. More specifically we have shown a role for bacteriocins in protecting against the potentially fatal foodborne pathogen Listeria monocytogenes. "As probiotics mechanisms are specific, thorough understanding of their beneficial effects are required. Understanding these mechanisms will enable their use in prevention and treatment of specific illnesses. This study clearly demonstrates how probiotic bacteria may help to improve the health of consumers." ​ Probiotic products containing 'friendly' bacteria are now well accepted by consumers in many European countries, with putative benefits highlighted for gut and immune health. Some of the researchers in this new study previously reported that a mixture of five Lactobacillus probiotic strains may reduce food poisoning by salmonella. In that instance, the benefits for gut health were reported to be due to the probiotic bacteria adhering to the walls of the intestine, which inhibits the ability of the pathogenic Salmonella to stick and colonise the gut, thereby reducing the infection. The new study offers an alternative method of protection, with a specific strain of Lactobacillus salivarius​ named UCC118 capable of producing an antibiotic-like compound called a bacteriocin. When the researchers tested UCC118 in mice infected with two strains of food-borne Listeria monocytogenes, EGDe and LO28, they found that the mice were protected against infection. When the mice were given a mutant form of the probiotic that was unable to produce the Abp118 bacteriocin, no protection against infection was observed. Also, "Lb. salivarius UCC118 did not offer any protection when mice were infected with a strain of L. monocytogenes expressing the cognate Abp118 immunity protein AbpIM, confirming that the antimicrobial effect is a result of direct antagonism between Lb. salivarius and the pathogen, mediated by the bacteriocin Abp118,"​ reported the researchers. "The results of the UCC work clearly demonstrate a role for bacteriocins in protecting the host against potentially lethal infections. The study is the first to clearly demonstrate a mechanism by which probiotic bacteria may act to help improve the health of consumers,"​ said a release from the university. Most foods containing probiotic bacteria are found in the refrigerated section of supermarkets as the bacteria is destroyed by heat and other processing conditions. This has given the dairy sector, already used to handling live bacteria for the manufacture of yoghurt, a major advantage in probiotic foods - probiotic drinking yoghurts are currently the fastest growing dairy product in Europe. But increasing research has focused on expanding protecting probiotics during processing and expanding the food categories available to prebiotics. Such an avenue of research has led companies like Cell Biotech from Korea using a dual-coating to protect probiotics against oxygen, acid, moisture and high temperatures for use in emerging new product categories such as breakfast cereals and smoothies. Other approaches are also being explored, with scientists looking at improving probiotic viability by using whey protein gel particles, or prebiotic fibres. Source: Proceedings of the National Academy of Sciences​ May 1, 2007, Volume 104, Number 18, Pages 7617-7621 "Bacteriocin production as a mechanism for the antiinfective activity of Lactobacillus salivarius UCC118" ​Authors: S.C. Corr, Y. Li, C.U. Riedel, P.W. O'Toole, C. Hill, and C.G.M. Gahan

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