Investigation into the beneficial maintenance of native gastointestinal flora and the inhibition of foodborne pathogens through the consumption of cranberry and lowbush wild blueberry.

摘要

Berries of plants in the genus Vaccinium family are distinct from other fruits because of their high concentration of phenolics, bioprotective effects, and antimicrobial properties. The primary objectives of this research are to determine which foodborne pathogens are susceptible to lowbush wild blueberry (LWB) and cranberry treatments in vitro, and investigate their impact on native gastrointestinal communities in vivo. This study investigates which components of berry extracts namely; organic acids, monomeric phenolics, anthocyanins, and proanthocyanidins, have antimicrobial properties and attempts to elucidate their mechanism of action against both pathogenic and probiotic microorganisms.;To determine the minimum inhibitory concentrations (MIC) of the different berry components, in vitro, extracts were diluted in series with culture broth, inoculated with pathogens of interest, and sampled at 0 and 24 hours to count microbial numbers. The results from these experiments demonstrated that pathogens such as Listeria monocytogenes, Salmonella Typhimurium, and Escherichia coli O157:H7 are twice as susceptible to berry extracts when compared to probiotic Lactobacillus rhamnosus. Cranberry fractions were neutralized and were analyzed for the MIC against E. coli O157:H7. The results demonstrated neutralization had did not change the MIC/MBC for phenolics while the MIC/MBC anthocyanins doubled. The antimicrobial mechanisms of cranberry and LWB were studied against Escherichia coli O157:H7 to determine the effects on growth inhibition, membrane permeability, and injury. It was found that cranberry and LWB affected the porosity of the plasma membrane and depending on environmental pH, could affect the distributional charge of the membrane.;In vivo investigations were conducted to observe the impacts LWB enriched diet on the native gastrointestinal flora of Sprague Dawley rats (Rattus rattus). Metagenomic analysis was used to assess the composition of the microbial community rat colon in response to the dietary change. Alterations in the relative abundance of 3 phyla and 22 genera were detected as a result of the treatment, representing approximately 14% and 8% of all classes and genera identified in the rat colon microbiota, respectively. The LWB-enriched dietary treatment resulted in a significant reduction in the relative abundance of the genera Lactobacilli and Enterococcus and an increase in Bifidobacteriaceae , Coriobacteriaceae, and Slackia. The functional repetoir of the microflora was accessed and protein families involved with integrase/recombinase, reverse transcriptase, and transposon/transposase were at a lower abundance in the LWB diet. These results reflect a possible alteration in the microbial community in response to the enriched presence of blueberries.;This is the first time that both in vitro and in vivo experiments have been conducted to investigate the impacts of Vaccinium berries on microbiological species. In addition this research demonstrates the antimicrobial properties of Vaccinium berries, which phytochemical constituent have these properties against which pathogen, and how they behave in vivo..