xiv, 207 leaves : ill., tables ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Microbiology, 1976

Thesis (Ph. D.)--University of Adelaide, 1989. / Includes bibliographical references.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Microbiology, 1976.

Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references.

Zugl.: Berlin, Humboldt-Univ., Diss., 2008

Thesis (Ph.D.)--University of North Carolina at Charlotte, 2005. / Includes bibliographical references (leaves 105-118).

München, Techn. Univ., Diss., 2002.

Salmonellosis is one of the most important foodborne zoonotic diseases throughout the world and poultry represents an important source of infection in humans. Chickens may become infected during incubation, in the brooding houses, through various vectors, such as feed and rodents or during slaughtering and processing. The use of antibiotics have been reduced and even banned in some countries, due to the risk of bacterial populations developing resistance against the antibiotics. This lead to the exploration of alternative products for antibiotics as growth promoters, which include prebiotics, probiotics, organic acids, essential oils, plant extracts and many more. These products may improve animal health, productivity and microbial food safety in a natural way. A feeding trial was conducted to investigate the effects of the dietary inclusion of probiotics and a prebiotic to improve the health and performance of broilers, which were challenged with Salmonella typhimurium. 1800 chicks (900 chicks exposed to Salmonella and 900 chicks not exposed) were randomly assigned to 6 dietary treatments for 5 weeks. The dietary treatments were: 1) No feed additives added, 2) A prebiotic (fructooligosaccharide) added to the feed, 3) Probiotic type 1 (Spore-forming bacteria) added to the feed, 4) Probiotic type 1 combined with the prebiotic added to the feed, 5) Probiotic type 2 (Lactobacillus spp.) added to the feed, 6) Probiotic type 2 combined with the prebiotic added to the feed. The feed intake, average daily gain and body weight of the control (nonchallenged) birds were significantly higher (P<0.05) than the Salmonella (challenged) birds. The Probiotic type 2 combined with the prebiotic improved the feed intake of the non-challenged birds compared to the non-challenged birds that received no supplementation or only a prebiotic. The challenged and non-challenged birds that did not receive any supplementation had lower body weights and average daily gains compared to the birds that received supplementation. The feed conversion ratio showed significant differences among the treatments (P<0.003) and between the control and Salmonella birds (P<0.05). The non-challenged birds fed the Probiotic type 2 combined with a prebiotic and the challenged birds fed only the prebiotic, displayed a decrease in liver weight, compared to the other treatments. However, the duodenum, jejunum and caeca weights of the broilers were significantly (P<0.05) enlarged shortly after Salmonella exposure through the inclusion of Probiotic type 1 and the two combination treatments in the diet. No significant differences were observed in the ileal weights after Salmonella exposure or after dietary supplementation. The total serum protein and the aspartate amino transferase (AST) levels showed no significant differences between the groups and treatments. However, the albumin levels of the challenged birds were significantly lower (P<0.05) than the non-challenged birds. The globulin levels were higher for the challenged birds that did not receive any supplementation than those that received a prebiotic and probiotics. The albumin: globulin ratios were higher for the non-challenged birds than the challenged birds. In general, the challenged birds tended to have more lesions than the non-challenged birds on the gastrointestinal tract (GIT). There were no significant differences in the villous height, mucosal thickness and crypt depth of the duodenum, jejunum and ileum. However, the control birds supplemented with Probiotic type 2 combined with a prebiotic showed a thicker mucosa layer than the control that received no supplementation. These findings indicate that the supplementation of a basal diet with probiotics and combination treatments of probiotics with a prebiotic can be used as growth promoters for broilers. These products, especially the Probiotic type 2 combined with the prebiotic, show promising effects as alternatives for antibiotics as pressure increases to eliminate the growth promotant antibiotics from being used in the livestock industry. / Dissertation (MSc(Agric))--University of Pretoria, 2011. / Animal and Wildlife Sciences / unrestricted

Wong Yin Wai. / Thesis submitted in: June 2002. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 82-93). / Abstracts in English and Chinese. / Acknowledgement --- p.ii / Abstract --- p.iii / 摘要 --- p.v / Table of Content --- p.vi / List of Tables --- p.ix / List of Figures --- p.x / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Taxonomy of salmonellae --- p.1 / Chapter 1.2 --- Clinical significance --- p.2 / Chapter 1.3 --- Treatment of Salmonella infections --- p.4 / Chapter 1.4 --- Global and local prevalence of Salmonella --- p.5 / Chapter 1.5 --- Antimicrobial Susceptibilities --- p.8 / Chapter 1.5.1 --- Salmonella Typhimurium --- p.8 / Chapter 1.5.2 --- Other salmonellae --- p.9 / Chapter 1.5.3 --- Emergence of quinolone-resistant salmonellae --- p.9 / Chapter 1.6 --- Mechanisms of β-lactam resistance --- p.10 / Chapter 1.6.1 --- Enzymatic deactivation of β-lactam antibiotics --- p.10 / Chapter 1.6.2 --- Modifications of normal PBPs --- p.11 / Chapter 1.6.3 --- Alternative routes of peptidoglycan synthesis --- p.12 / Chapter 1.6.4 --- Impermeability and active efflux system --- p.12 / Chapter 1.7 --- Classification and nomenclature of β-lactamases --- p.13 / Chapter 1.7.1 --- Functional classification --- p.13 / Chapter 1.7.2 --- Molecular classification --- p.15 / Chapter 1.7.3 --- Nomenclature of β-lactamases --- p.16 / Chapter 1.8 --- β-Lactamases in salmonellae --- p.17 / Chapter 1.8.1 --- Salmonella Typhimurium --- p.17 / Chapter 1.8.2 --- Other salmonellae --- p.18 / Chapter 1.9 --- Methods for the characterization of β-lactamases --- p.18 / Chapter 1.9.1 --- Isoelectric focusing (IEF) --- p.19 / Chapter 1.9.2 --- β-Lactamase activity assays --- p.20 / Chapter 1.9.3 --- Hybridization with DNA probes --- p.20 / Chapter 1.9.4 --- Amplification of β-lactamase genes by polymerase chain reaction (PCR) --- p.21 / Chapter 1.9.5 --- Polymerase chain reaction - Single strand conformational polymorphism (PCR-SSCP) analysis --- p.23 / Chapter 1.9.6 --- Gene sequencing --- p.23 / Chapter 1.10 --- Objectives --- p.25 / Chapter 2 --- Materials and Methods --- p.26 / Chapter 2.1 --- Bacterial Strains --- p.26 / Chapter 2.1.1 --- Identification of salmonellae --- p.26 / Chapter 2.1.2 --- Antibiotics and chemicals used --- p.26 / Chapter 2.1.3 --- Antimicrobial susceptibility testing --- p.28 / Chapter 2.2 --- Localization of β-lactamase genes --- p.30 / Chapter 2.2.1 --- Transferability study --- p.30 / Chapter 2.3 --- Characterization of β-lactamases --- p.31 / Chapter 2.3.1 --- Extraction of crude β-lactamases --- p.31 / Chapter 2.3.2 --- Isoelectric focusing (IEF) --- p.31 / Chapter 2.4 --- Molecular characterization of β-lactamase genes --- p.33 / Chapter 2.4.1 --- Detection of TEM-type β-lactamase genes using polymerase chain reaction (PCR) --- p.33 / Chapter 2.4.2 --- Detection of OXA-type β-lactamase gene using PCR --- p.36 / Chapter 2.4.3 --- Detection of TEM mutations by polymerase chain reaction 一 single strand conformational polymorphism (PCR-SSCP) analysis --- p.37 / Chapter 2.4.4 --- Detection of OXA mutations by PCR-SSCP analysis --- p.38 / Chapter 2.4.5 --- Sequencing of β-lactamase genes --- p.39 / Chapter 2.4.5.1 --- Preparation of sequencing template --- p.39 / Chapter 2.4.5.2 --- Sequencing reaction --- p.39 / Chapter 2.4.5.3 --- Preparation of sequencing gel --- p.40 / Chapter 2.4.5.4 --- Silver staining of the sequencing gel --- p.41 / Chapter 2.5 --- Relatedness of ampicillin-resistant S. Typhimurium --- p.42 / Chapter 2.5.1 --- Pulsed field gel electrophoresis (PFGE) --- p.42 / Chapter 2.5.2 --- Cluster analysis --- p.44 / Chapter 3 --- Results --- p.46 / Chapter 3.1 --- Bacterial Strains --- p.46 / Chapter 3.1.1 --- Antimicrobial susceptibilities --- p.46 / Chapter 3.2 --- Characterization of β-lactamases by isoelectric focusing --- p.52 / Chapter 3.3 --- Characterization of β-lactamase genes --- p.53 / Chapter 3.3.1 --- Transferability of β-lactamase genes --- p.53 / Chapter 3.3.2 --- Detection of OXA-type β-lactamase gene by polymerase chain reaction (PCR) --- p.53 / Chapter 3.3.3 --- Detection of OXA-type mutations by polymerase chain reaction- single strand conformational polymorphism (PCR-SSCP) analysis --- p.56 / Chapter 3.3.4 --- Detection of TEM-type β-lactamase gene by PCR --- p.56 / Chapter 3.3.5 --- Detection of TEM-type mutations by PCR-SSCP analysis --- p.56 / Chapter 3.3.6 --- Sequencing of β-lactamase genes --- p.61 / Chapter 3.3.7 --- Pulsed-field gel electrophoresis --- p.64 / Chapter 4 --- Discussion --- p.67 / Chapter 4.1 --- Antimicrobial susceptibilities of S. Typhimurium in Hong Kong --- p.67 / Chapter 4.2 --- Transferability of resistance --- p.69 / Chapter 4.3 --- β-Lactamases of S. Typhimurium --- p.70 / Chapter 4.4 --- DNA sequence of β-lactamase genes --- p.72 / Chapter 4.5 --- Relatedness of ampicillin-resistant S. Typhimurium --- p.73 / Chapter 4.6 --- Methods for the characterization of β-lactamases --- p.75 / Chapter 4.7 --- Significance of this study --- p.78 / Chapter 4.8 --- Conclusions --- p.79 / Chapter 4.9 --- Further studies --- p.80 / References --- p.83

Although dialkylnitrosamines are environmentally significant carcinogens, the use of short-term bioassays to assess the mutagenic potential of these compounds remains problematic. The Ames test, a mutagenicity assay based on the reversion of Salmonella typhimurium histidine auxotrophs, is the most widely used bioassay in genetic toxicology, but the traditional Ames tester strains are largely insensitive to dialkylnitrosamine mutagenicity. I have constructed several mutagenicity tester strains that co-express combinations of full-length human cytochrome P450 2E1, rat cytochrome P450 reductase, and human cytochrome b5 in S. typhimurium lacking ogt and ada methyltransferases (YG7104ER, ogt-; and YG7108ER, ogt-, ada-). These new strains are susceptible to dialkylnitrosamine mutagenicity in the absence of an exogenous metabolic activating system (S9 fraction). Mutagenicity is dependent upon the coexpression of P450 2E1 with P450 reductase and is similar or greater than that obtained with the parental strains in the presence of S9 fraction from ethanol-induced rat liver. Coexpressing human cytochrome b5 with cytochrome P450 2E1 and cytochrome P450 reductase potentiates the mutagenicity observed with dialkylnitrosamines. These strains were sensitive to nitrosamines with varying alkyl side chains, including dimethylnitrosamine, diethylnitrosamine, dipropylnitrosamine, and dibutylnitrosamine. Mutagenicity decreased with alkyl chain length, consistent with the stringency of the ada-encoded enzyme for methyl and ethyl DNA adducts. These new strains may prove useful in the evaluation of nitrosamine contamination of food and environmental samples, and may serve as useful tools in investigating the molecular properties of proteins in the cytochrome P450 monooxygenase system.