Submitted to: Proceedings of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: 5/7/2002
Publication Date: N/A
Technical Abstract: The term probiotics has historically been used to describe the delivery of live microbes to humans and animals benefiting the host by improving its intestinal microbial balance. The term now encompass the delivery of complex preparations of bacteria to animals early in their life to help in the prevention of gastrointestinal colonization by enteropathogens. These competitive exclusion cultures have been maintained in our laboratory under in vitro continuous flow culture conditions and have been shown to significantly reduce cecal colonization by Salmonella typhimurium in broiler chicks. Among the postulated mechanisms for the beneficial actions of these cultures is the possibility that they produce substances which are bactericidal to other bacteria including S. typhimurium. We hypothesized that the some bacteria in the culture could produce bacterial derived microvesicles which contain bactericidal compounds. Isolated microvesicles co-incubated with 105 colony-forming units per milliliter (CFU/ml) of S. typhimurium resulted in a two log reduction of S. typhimurium CFU/ml after two hours of incubation. Similar reductions were obtained when cell free extracts were co-incubated with an isolate of E. coli. Thin sectioned material examined by transmission electron microscopy contained single membrane-bounded vesicles of various morphologies. These results indicate that bacterial microvesicles produced in vitro by competitive exclusion bacteria grown under continuous flow culture conditions may act as a delivery system for bacterial derived bactericidal compounds. These findings also suggest that microvesicles may contribute to the beneficial effects of competitive exclusion cultures when administered in vivo.