Masters Degrees (Microbiology)

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Browsing Masters Degrees (Microbiology) by Author "Botha, Marlie"

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    Selection of probiotic lactic acid bacteria for horses based on in vitro and in vivo studies
    (Stellenbosch : Stellenbosch University, 2011-12) Botha, Marlie; Dicks, Leon Milner Theodore; Botes, Marelize; Stellenbosch University. Faculty of Sciences. Dept. of Microbiology.
    ENGLISH ABSTRACT: The equine gastro-intestinal tract (GIT) is a relatively unexplored niche concerning the presence of natural microbiota. Studies have shown that disruption of the microbial population naturally present in the GIT leads to the onset of several forms of gastro-intestinal disorders. To maintain a balanced microbiota, probiotic bacteria need to be administered at specific levels. Beneficial microorganisms assist with digestion of the feed, absorption of nutrients from the GIT, strengthens the immune system and improves the animal‟s growth. Various combinations of lactic acid bacteria (LAB) have been administered to horses, but have failed to benefit the host in any of the latter criteria. The screening for alternative strains with probiotic properties is thus necessary. Two strains (Lactobacillus equigenerosi Le1 and Lactobacillus reuteri Lr1) were originally isolated from horse faeces. Lactobacillus plantarum 423 and Enterococcus mundtii ST4SA, both bacteriocin-producing strains, were isolated from sorghum beer and soy beans, respectively. All four strains survived growth at acidic conditions (pH 3) and the presence of 0.5%, 1.0% and 1.5% (w/v) bile salts. L. reuteri Lr1 was the most resistant to these conditions. All strains adhered to buccal (cheek) epithelium cells sampled from horses. L. equigenerosi Le1 and E. mundtii ST4SA, however, invaded the cells, but without visible signs of disrupting the cells. None of the strains contained genes encoding adhesion to collagen (Ace), resistance to vancomycin A, B and C, or, production of aggregation substance (AS), cytolysin (Cyl) and, non-cytolysin (β hemolysin III), suggesting that they are non-virulent. Of all strains, L. equigenerosi Le1 competed the best with Clostridium sp. C6 for adherence to epithelial cells. L. equigenerosi Le1 and L. reuteri Lr1, showed the highest level of co-aggregation with Clostridium sp. C6. When the four strains were administered to horses over a period of 10 days, L. reuteri Lr1 was retained the longest (8 days) in the GIT. The numbers of viable cells of Clostridium spp. and Salmonella spp. remained constant during administration of the four strains. Blood analyses showed no negative effects from administering the strains. Total white blood cell counts remained unchanged. However, a small but tentative increase in neutrophil and eosinophil cell numbers has been recorded, suggesting that the LAB may have elicited a mild, transient, intolerance reaction. The glucose, lactate and urea levels decreased during administration with the four LAB strains.