Thesis (Ph. D. veterinary science)--Washington State University, August 2008. / Includes bibliographical references.

Jin Yongjie. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 138-171). / Abstracts in English and Chinese. / Abstract (in English) --- p.i / Abstract (in Chinese) --- p.iii / Acknowledgments --- p.iv / Table of Contents --- p.v / List of Tables --- p.x / List of Figures --- p.xi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1. --- Salmonella --- p.1 / Chapter 1.1 --- Morphology --- p.1 / Chapter 1.2 --- Antigenic structure --- p.1 / Chapter 1.3 --- Identification --- p.2 / Chapter 1.4 --- Nomenclature and classification --- p.2 / Chapter 1.5 --- Pathogenesis and virulence --- p.3 / Chapter 1.6 --- Infections --- p.4 / Chapter 1.6.1 --- Enteric fever --- p.4 / Chapter 1.6.2 --- Gastroenteritis --- p.4 / Chapter 1.7 --- Treatment --- p.5 / Chapter 1.7.1 --- Enteric fever --- p.5 / Chapter 1.7.2 --- Gastroenteritis --- p.5 / Chapter 1.8 --- Epidemiology and control --- p.6 / Chapter 1.8.1 --- Enteric fever --- p.6 / Chapter 1.8.2 --- Salmonella food poisoning --- p.6 / Chapter 2. --- Fluoroquinolones --- p.6 / Chapter 2.1 --- History of fluoroquinolones --- p.8 / Chapter 2.2 --- Mechanisms of action --- p.9 / Chapter 3. --- Antimicrobial resistance --- p.10 / Chapter 3.1 --- Microorganism-mediated resistance --- p.10 / Chapter 3.1.1 --- Intrinsic resistance --- p.11 / Chapter 3.1.2 --- Acquired resistance --- p.11 / Chapter 3.2 --- Resistance due to environmental factors --- p.12 / Chapter 3.3 --- Biological and clinical resistance --- p.12 / Chapter 3.4 --- Breakpoints --- p.13 / Chapter 4. --- Fluoroquinolone-resistance --- p.14 / Chapter 4.1 --- Increasing fluoroquinolone-resistance in bacteria --- p.14 / Chapter 4.2 --- Mechanisms of resistance to fluoroquinolones --- p.16 / Chapter 4.2.1 --- Mutations of target genes --- p.17 / Chapter 4.2.2 --- Active efflux systems and decreased membrane permeability --- p.20 / Chapter 5. --- Fluoroquinolone-resistance in Salmonella --- p.21 / Chapter 5.1 --- Prevalence of fluoroquinolone-resistant salmonellae in man and Animals --- p.21 / Chapter 5.1.1 --- Prevalence in the world --- p.21 / Chapter 5.1.2 --- Increasing resistance trend in Hong Kong --- p.24 / Chapter 5.2 --- Clinical outcome --- p.25 / Chapter 5.3 --- Mechanisms of fluoroquinolone-resistance in Salmonella --- p.25 / Chapter 5.3.1 --- Target gene mutations --- p.25 / Chapter 5.3.2 --- Other resistance mechanisms --- p.28 / Chapter 5.3.3 --- In vitro development of Salmonella resistant mutants --- p.29 / Chapter 6. --- Restricting the development of resistant mutants --- p.31 / Chapter 6.1 --- Mutant prevention concentration (MPC) --- p.31 / Chapter 6.1.1 --- Definition --- p.31 / Chapter 6.1.2 --- Development of MPC concept --- p.31 / Chapter 6.1.3 --- Significance --- p.34 / Chapter 6.2 --- Mutant selection window (MSW) --- p.35 / Chapter 6.2.1 --- The concept of mutant selection window (MSW) --- p.35 / Chapter 6.2.2 --- Significance --- p.36 / Chapter 7. --- Detection of gene mutations --- p.37 / Chapter 8. --- Objectives --- p.37 / Chapter Chapter 2 --- Materails and Methods --- p.39 / Chapter 1. --- Materials --- p.39 / Chapter 1.1 --- Bacterial strains --- p.39 / Chapter 1.1.1 --- Bacterial strains used for this study --- p.39 / Chapter 1.1.2 --- Storage of bacterial strains --- p.39 / Chapter 1.2 --- Materials --- p.40 / Chapter 2. --- Methods --- p.40 / Chapter 2.1 --- Identification --- p.40 / Chapter 2.2 --- Microbiological methods --- p.40 / Chapter 2.2.1 --- Determination of minimal inhibitory concentration (MIC) --- p.40 / Chapter 2.2.1.1 --- Preparation of antibiotic plates --- p.40 / Chapter 2.2.1.2 --- Preparation of inoculum --- p.43 / Chapter 2.2.1.3 --- Inoculation of antibiotic plates --- p.43 / Chapter 2.2.2 --- Determination of mutant prevention concentration (MPC) --- p.43 / Chapter 2.2.2.1 --- Preparation of bacterial suspension --- p.43 / Chapter 2.2.2.2 --- Inoculation of bacterial suspension --- p.43 / Chapter 2.2.2.3 --- Determination of the size of the inoculum --- p.43 / Chapter 2.2.2.4 --- Reading of results --- p.45 / Chapter 2.3 --- Molecular methods --- p.45 / Chapter 2.3.1 --- Polymerase chain reaction (PCR) --- p.45 / Chapter 2.3.2 --- Agarose gel electrophoresis --- p.47 / Chapter 2.3.3 --- Multiplex PCR amplimer conformation (MPAC) analysis --- p.47 / Chapter 2.3.3.1 --- Preparation of samples --- p.47 / Chapter 2.3.3.2 --- Electrophoresis --- p.49 / Chapter 2.3.3.3 --- Silver staining --- p.49 / Chapter 2.3.4 --- DNA Sequencing --- p.50 / Chapter 2.3.4.1 --- Purification of PCR products --- p.50 / Chapter 2.3.4.2 --- Sequencing reactions --- p.50 / Chapter 2.3.4.3 --- Electrophoresis --- p.50 / Chapter 2.3.4.4 --- Silver staining --- p.52 / Chapter 2.4 --- Stepwise selection and characterization of mutants --- p.53 / Chapter 2.4.1 --- In vitro selection of first-step strains --- p.53 / Chapter 2.4.2 --- Characterization of selected strains --- p.53 / Chapter 2.4.3 --- Subsequent selection of stepwise mutants --- p.54 / Chapter 3. --- Research plan --- p.54 / Chapter Chapter 3 --- Results --- p.55 / Chapter 1. --- Identification and fluoroquinolone MICs of Salmonella strains --- p.55 / Chapter 1.1 --- Identification of Salmonella strains --- p.55 / Chapter 1.2 --- Fluoroquinolone MICs for Salmonella strains --- p.55 / Chapter 1.2.1 --- Salmonella Typhimurium --- p.55 / Chapter 1.2.2 --- Salmonella Hadar --- p.57 / Chapter 2. --- Mutant prevention concentration (MPC) --- p.57 / Chapter 2.1 --- Salmonella Typhimurium --- p.57 / Chapter 2.1.1 --- MPC value --- p.57 / Chapter 2.1.2 --- MPC/MIC ratio --- p.57 / Chapter 2.1.3 --- Cmax/MPC ratio --- p.60 / Chapter 2.1.4 --- Frequencies of development of resistant strains --- p.60 / Chapter 2.2 --- Salmonella Hadar --- p.63 / Chapter 2.2.1 --- MPC value --- p.63 / Chapter 2.2.2 --- MPC/MIC ratio --- p.63 / Chapter 2.2.3 --- Cmax/MPC ratio --- p.63 / Chapter 2.2.4 --- Frequencies of development of resistant strains --- p.65 / Chapter 3. --- Stepwise selection of resistant mutants --- p.65 / Chapter 3.1 --- Salmonella Typhimurium --- p.70 / Chapter 3.1.1 --- Characterization of 1 St-step strains --- p.70 / Chapter 3.1.1.1 --- Antimicrobial susceptibilities --- p.70 / Chapter 3.1.1.2 --- Characterization of gene mutations --- p.75 / Chapter 3.1.1.3 --- Mutations and fluoroquinolone susceptibilities --- p.80 / Chapter 3.1.1.4 --- Mutations and nalidixic acid susceptibilities --- p.81 / Chapter 3.1.2 --- Characterization of 2nd-step mutants --- p.81 / Chapter 3.1.2.1 --- Antimicrobial susceptibilities --- p.82 / Chapter 3.1.2.2 --- Characterization of gene mutations --- p.85 / Chapter 3.1.2.3 --- Mutations and fluoroquinolone susceptibilities --- p.87 / Chapter 3.1.2.4 --- Nalidixic acid susceptibilities --- p.87 / Chapter 3.1.3 --- Characterization of 3rd-step mutants --- p.88 / Chapter 3.1.3.1 --- Antimicrobial susceptibilities --- p.88 / Chapter 3.1.3.2 --- Characterization of gene mutations --- p.92 / Chapter 3.1.3.3 --- Mutations and fluoroquinolone susceptibilities --- p.94 / Chapter 3.1.3.4 --- Nalidixic acid susceptibilities --- p.95 / Chapter 3.1.4 --- Characterization of 4th-step mutants --- p.95 / Chapter 3.1.4.1 --- Antimicrobial susceptibilities --- p.95 / Chapter 3.1.4.2 --- Characterization of gene mutations --- p.98 / Chapter 3.1.4.3 --- Nalidixic acid susceptibilities --- p.98 / Chapter 3.2 --- Salmonella Hadar --- p.98 / Chapter 3.2.1 --- Characterization of 1 St-step strains --- p.98 / Chapter 3.2.1.1 --- Antimicrobial susceptibilities --- p.99 / Chapter 3.2.1.2 --- Characterization of gene mutations --- p.102 / Chapter 3.2.1.3 --- Mutations and fluoroquinolone susceptibilities --- p.107 / Chapter 3.2.1.4 --- Mutations and nalidixic acid susceptibilities --- p.108 / Chapter 3.2.2 --- Characterization of 2nd-step mutants --- p.109 / Chapter 3.2.2.1 --- Antimicrobial susceptibilities --- p.109 / Chapter 3.2.2.2 --- Characterization of gene mutations --- p.112 / Chapter 3.2.2.3 --- Mutations and fluoroquinolone susceptibilities --- p.112 / Chapter 3.2.2.4 --- Nalidixic acid susceptibilities --- p.113 / Chapter Chapter 4 --- Discussion --- p.114 / Chapter 1. --- Susceptibility of salmonellae to fluoroquinolones --- p.114 / Chapter 2. --- The potential of fluoroquinolones to restrict the development of Salmonella resistant strains --- p.114 / Chapter 2.1 --- MPC and MPC/MIC of fluoroquinolones --- p.115 / Chapter 2.2 --- Cmax/MPC of fluoroquinolones --- p.117 / Chapter 2.3 --- Selection frequency of fluoroquinolones --- p.118 / Chapter 2.4 --- Effects of fluoroquinolones on the development of resistancein Salmonella Typhimurium and Salmonella Hadar --- p.119 / Chapter 3. --- Characterization of in vitro fluoroquinolone-resistant Salmonella mutants --- p.120 / Chapter 3.1 --- Development of resistance phenotype --- p.120 / Chapter 3.1.1 --- Microbiology --- p.120 / Chapter 3.1.2 --- Antimicrobial susceptibilities --- p.120 / Chapter 3.1.2.1 --- First-step strains --- p.120 / Chapter 3.1.2.2 --- Second-step mutants --- p.121 / Chapter 3.1.2.3 --- Third-step mutants --- p.121 / Chapter 3.1.2.4 --- Fourth-step mutants --- p.122 / Chapter 3.2 --- Contribution of target gene mutations to resistance development --- p.122 / Chapter 3.2.1 --- First-step mutants --- p.122 / Chapter 3.2.2 --- Second-step mutants --- p.125 / Chapter 3.2.3 --- Third-step mutants --- p.126 / Chapter 3.2.4 --- Fourth-step mutants --- p.128 / Chapter 3.3 --- The sequential development of gene mutations --- p.129 / Chapter 3.4 --- Other fluoroquinolone-resistance mechanisms --- p.130 / Chapter 4. --- Mutations and susceptibilities to fluoroquinolones and nalidixic acid --- p.132 / Chapter 4.1 --- Nalidixic acid - a marker for resistance to fluoroquinolones --- p.132 / Chapter 4.2 --- Breakpoint and clinical efficiency --- p.133 / Chapter 5. --- Strategies to reduce development of fluoroquinolone-resistance --- p.134 / Chapter 6. --- Conclusion --- p.136 / Chapter 7. --- Areas for future research --- p.136 / References --- p.138

Thesis (Ph.D.) - University of Glasgow, 2008. / Ph.D. thesis submitted to the Department of Infection and Immunity, Faculty of Biomedical and Life Sciences, University of Glasgow, 2008. Includes bibliographical references. Print version also available.

published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

Extended spectrum (3-lactamases (ESBLs) were characterized in Salmonella spp. isolates from a pediatric ward of a hospital in Durban. Forty one Salmonella spp. were subjected to serotyping, antibiotic susceptibility testing, E-Tests for ESBL detection, iso-electric focusing, polymerase chain reaction for detection of genes and sequencing. Isolates were screened for the presence of WaTEM, WaSHV, WaCTX-M, WaOXA , WaCMY, WaDHA and WaACC genes. The most common serotype was Salmonella Typhimurium. Isolates were multi-drug resistant with 100% susceptibility only to meropenem and ciprofloxacin. Tazobactam was the most effective inhibitor. Forty-one percent of the isolates were resistant to ceftriaxone, thus limiting therapeutic options for Salmonella infections.TEM-1 was the most predominant (3-lactamase found in 51% of isolates while SHV-12 found in 39 % was the most common ESBL. TEM-63 was evident in 29 %, TEM-116 in 10 % and TEM-131 was found in one isolate. The high ceftazidime MICs of isolates expressing only TEM-63 were indicative of R164S substitution which widens the binding cavity to accommodate the bulky side chains of oxyiminoaminothiazolyl cephalosporins. The identification of TEM-131 which differs from TEM-63 by 1 amino acid reiterates the evolutionary potential of the TEM-type plactamase. Other ESBLs identified included SHV-2, CTX-M-3, CTX-M-15 and CTX-M-37. CMY-2 and the OXA-1 p-lactamase were also detected. This is the first report of TEM-116, CTX-M-3, -15 and -37 in Salmonella spp. in South Africa. All isolates with nalidixic acid MICs > 48 ug/ml had the mutation D87N, or D87G in the QRDR of the gyrA gene. This study showed that Salmonella spp. may be multi-drug resistant with the propensity to harbour p-lactamases in unique combinations. The diversity of ESBLs and the co-expression of quinolone resistance suggests that their incidence in salmonellae needs to be monitored. / Thesis (Ph.D.)-University of KwaZulu-Natal, 2008.

Thesis (Ph.D.)--Michigan State University. Dept. of Food Science and Human Nutrition, 2008. / Title from PDF t.p. (viewed on Mar. 27, 2009) Includes bibliographical references (p.108-118). Also issued in print.

The thesis is concerned with what should be done to decrease the incidence of human salmonellosis in Canada. The present high incidence of Salmonella contaminated poultry is reviewed and evidence is given that links Salmonella contaminated poultry carcasses at the retail level to human salmonellosis. The question is raised as to whether control or eradication should be the goal in Canada, and present regulations involving various levels of Governments are examined. The incidence of Salmonella contaminated poultry in some other countries is reviewed, together with some of the Salmonella control programmes that have been instituted by these countries. Finally, certain recommendations are made, as to what could be done in Canada to decrease the incidence of human salmonellosis. These recommendations stress the need for further research to develop ways of decreasing the incidence of Salmonella contaminated poultry at the retail level. The colonization of the gut of day-old chickens with the intestinal flora of adult chickens is a method that shows promise. The use of radiation and chlorination of the poultry carcasses would also help to reduce the incidence of carcass contamination. If Canada is determined to reduce human salmonellosis, then steps must be taken to coordinate the many different branches of both the Federal and Provincial Governments, and regulations, when promulgated, must be enforced. Caterers and those cooking in their own homes must be educated on correct food handling practices and cooking techniques. Human salmonellosis will probably never be eradicated, but its present incidence could certainly be reduced. / Medicine, Faculty of / Population and Public Health (SPPH), School of / Graduate

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Food Science." Includes bibliographical references (p. 115-125).

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 105-123).

Despite the development of various systems to generate live recombinant Salmonella Typhimurium vaccine strains, little work has been performed to systematically evaluate and compare their relative immunogenicity. Such information would provide invaluable guidance for the future rational design of live recombinant Salmonella oral vaccines. Here, a series of recombinant Salmonella Typhimurium strains were constructed to express either the enhanced green fluorescent protein (EGFP) or a fragment of the hemagglutinin (HA) protein from the H5N1 influenza virus, as model antigens. To investigate different delivery and expression methods, antigens were expressed from the chromosome, from high or low-copy plasmids, or encoded on a eukaryotic expression plasmid. Antigens were targeted for expression in the cytoplasm, or the outer membrane. In addition, combinations of two expression strategies were employed to evaluate the efficacy of combined delivery approaches. After investigating in vitro and in vivo antigen expression, growth and infection abilities, the immunogenicity of the constructed recombinant Salmonella strains was evaluated and compared in mice. Using soluble model antigen EGFP, my results indicated that vaccine strains with high and stable antigen expression exhibited high B cell responses, while eukaryotic expression or colonization with good construct stability is critical for T cell responses. For insoluble antigen model HA, the outer membrane strategy induced better B cell and T cell responses than cytoplasmic strategy. Most notably, the combination of two different expression strategies did not increase the immune response elicited as initially expected. Based on the advantages, deleterious or synergistic effects of different strategies identified in this study, I conclude that different construction strategies of recombinant Salmonella vaccine strains are needed for different forms of antigens (soluble or insoluble antigens). If the antigen (such as EGFP) is soluble and easily expressed in Salmonella, a low-copy plasmid-based strategy should be employed, as it can provoke both strong B cell and T cell responses with better plasmid stability. If a T cell response is preferred, a eukaryotic plasmid, or chromosome-based, cytoplasmic-expression strategy may achieve better results. For heterologous antigens that are likely to be expressed in an insoluble form inside Salmonella (such as HA), an outer membrane-targeting approach is recommended. In addition, I found that the combination of two expression strategies did not enhance the immune response, and hence I caution the use of such an approach. / published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy