Graduate Thesis Or Dissertation
 

Effect of feeding concentrates of Lactobacillus organisms on intestinal colonization by Escherichia coli in swine

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  • A Lactobacillus species of human intestinal origin (strain MLC) used in swine feeding experiments was characterized using biochemical, genetic and serological techniques and found to be Lactobacillus lactis. Bottle feeding of the MLC strain in concentrate form (> 10⁹ cfu/ml) resulted in a reduction in both fecal coliforms and the incidence of scouring. In one group of pigs which received concentrate for 54 days, the Lactobacillus to coliform ratio was 1280:1; in the control group the ratio was 2.3:1. To increase the sample size, a herd of 125 swine was fed concentrates of Lactobacillus lactis MLC through the drinking water system using a water proportioner. After 90 days of such treatment, the coliform counts were reduced by 95%. The scouring incidence in the treated pigs was 13% as compared to 35% in the control group. However numbers of fecal lactobacilli were not increased. The influence of Lactobacillus MLC feeding on the bacterial flora of different parts of gastrointestinal tract was studied. In the case of scouring pigs, enteropathogenic Escherichia coli (EEC) were present in larger numbers in the tissue homogenate of different parts of the tract than in the lumen. The virulence of the EEC found present was confirmed by experimental infection in pigs. In control, non-scouring pigs only non-EEC were found in the tissue. In Lactobacillus MLC-fed pigs, E. coli both in the tissue and lumen was reduced to low numbers; also, the few E. coli observed were non-enteropathogenic. Thus by feeding Lactobacillus MLC concentrate, it was possible to reduce the E. coli to less than 10² /gm There were higher numbers of lactobacilli in the tissues of Lactobacillus-fed pigs than in control and scouring pigs. The lactobacilli isolated from tissue homogenate of the treated animals resembled biochemically and serologically (fluorescent antibody staining) the Lactobacillus MLC which was fed. Histological studies were done to show direct evidence of colonization in frozen sections of intestine obtained from Lactobacillus MLC-fed pigs. Gram and toluidine blue-staining revealed large numbers of Gram-positive bacilli colonizing the surface epithelium of the villi. On the other hand, control pigs which died of scouring revealed many EEC colonizing the small intestine. Pigs in groups receiving colostrum and lactobacilli performed very well. No symptoms of diarrhea was seen and many lactobacilli colonized throughout the small intestine. Even after the challenge with EEC serotype 09:K:NM, these two groups of pigs did not show any signs of disease and very few EEC colonized the intestines even after the challenge. Pigs not receiving colostrum but only lactobacilli did not scour before challenge with EEC 09:K:NM and many lactobacilli colonized the small intestine. However, 72 hours after challenge these latter animals revealed symptoms of diarrhea and EEC were seen colonizing the small intestine in addition to lactobacilli. The possible role of surface antigens in colonization by lactobacilli was studied. Data revealed that Lactobacillus lactis MLC and L. salivarius did not have any antigens in common. On the other hand, Lactobacillus FHS isolated from pig intestine had three antigens in common with the MLC strain. However, in vivo tests showed that all three strains colonized the small intestine to the same degree. This indicated that surface antigens were not involved in the colonization mechanism. The ability of Lactobacillus MLC to inhibit a variety of intestinal pathogens in broth cultures was demonstrated. Organisms inhibited included E. coli, Staphylococcus aureus, Clostridium perfringens and Bacterotdes sp. The mechanism of inhibition of S. aureus and E. coli in milk and broth was examined. These organisms did not grow in cell-free culture supernatants (whey at pH 4.0) after growth of the Lactobacillus MLC but they grew well in broth adjusted to pH 4.0 Supernatant from cultures of Lactobacillus MLC concentrate was found to contain 2-Deoxy-D-glucose in addition to glucose and galactose. Studies using 2-Deoxy-D-glucose alone and with glucose and galactose showed that the former was inhibitory to E. coli, S. aureus and Salmonella typhimurium. Possible applications of these findings in the animal industry as a substitute to antibiotics are discussed. A greater use of Lactobacillus organisms in preventive treatment of intestinal diseases is suggested.
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file details MuralidharaKS1974.pdf 2017-08-17 Pubblico Scaricare