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Research Project: Identification of the Ecological Niches and Development of Intervention Strategies to Reduce Pathogenic Foodborne Pathogens in Poultry

Location: Food and Feed Safety Research

Title: Inhibitory effect of supernatants from a competitive exclusion culture over growth of some intestinal pathogens

Author
item Aguilar-rivera, Catalina - Universidad De La Sabana
item Hume, Michael
item Klotz-ceberio, Bernadette - Alpina Research Institute

Submitted to: Revista Mexicana de Ingenieria Quimica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2016
Publication Date: 8/1/2016
Publication URL: http://handle.nal.usda.gov/10113/5852140
Citation: Aguilar-Rivera, C., Hume, M.E., Klotz-Ceberio, B.F. 2016. Inhibitory effect of supernatants from a competitive exclusion culture over growth of some intestinal pathogens. Revista Mexicana de Ingenieria Quimica. 15(2):379-389.

Interpretive Summary: Competitive exclusion cultures, which use whole bacterial communities derived directly from the gastrointestinal tract, have been effective in controlling pathogens in livestock, but their application in humans has not been widely studied. In this study, growth medium from which the bacteria were removed was obtained from a competitive exclusion culture developed from fecal samples collected from healthy humans. The inhibitory effects of the bacteria-free growth medium were examined against growth of intestinal pathogens of public health significance: Shigella sonnei, E. coli, and Salmonella Enteritidis. Growth rates and pathogen concentrations were significantly reduced by the growth medium for the most sensitive bacterium, Shigella sonnei, and moderately for the most resistant, Salmonella Enteritidis. A growth delay of more than 14 hours was present in both Shigella sonnei and E. coli. Treating the growth medium by heat and protein digestion revealed the effects on the bacteria were likely due to a bacteria-killing substance called bacteriocin. The competitive exclusion culture developed has biotechnological potential for the production of novel antimicrobials of interest to the food and pharmaceutical industries.

Technical Abstract: Competitive exclusion cultures (CEC), which use whole bacterial communities derived directly from the gastrointestinal tract, have been effective in controlling pathogens in animals, but their application in humans have not been widely studied. In this work, the inhibitory effect of supernatants obtained from a CEC developed from fecal samples of healthy individuals was examined on the growth of intestinal pathogens which are of public health significance. The Baranyi Model was adjusted (R-square > 0.947) to growth curves of Shigella sonnei (SF1), E. coli EPEC (EC6), and Salmonella Enteritidis (SE3) treated with supernatants in order to estimate kinetic parameters. Growth rates and pathogen concentrations were significantly reduced by the action of supernatants in 89.89% and 86.80%, respectively, for the most sensitive bacteria (SF1) and 23.21% and 36.86% for the most resistant (SE3). A growth delay of more than 14 hours was presented by SF1 and EC6 with the treatments. Thermal and enzymatic (proteinase K and trypsin) sensitivity of supernatants indicates that antagonism was mediated by bacteriocin-like substances. The CEC developed has biotechnological potential for the production of antimicrobial substances of interest in the food and pharmaceutical industries.