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by Norman Wai-sing Lo. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 145-160). / Chapter Chapter 1 --- Introduction --- p.1 / Chapter A. --- Classification of Salmonella --- p.3 / Chapter B. --- Enteric fever --- p.4 / Chapter C. --- Chloramphenicol and multiple resistance in S. Typhi --- p.7 / Chapter D. --- Resistance plasmids in the typhoid bacillus --- p.11 / Chapter E. --- In vivo acquisition of resistance plasmids by S. Typhi --- p.18 / Chapter F. --- Worldwide distribution of typhoid fever --- p.23 / Chapter G. --- Epidemiology of typhoid fever in Hong Kong --- p.27 / Chapter H. --- Principles of methods used in the epidemiological typing of S. Typhi --- p.29 / Chapter 1. --- Phage typing --- p.29 / Chapter 2. --- Antibiotics sensitivity pattern --- p.32 / Chapter 3. --- Plasmid analyses --- p.32 / Chapter a. --- Genetic methods --- p.33 / Chapter i. --- Phenotypic expression --- p.33 / Chapter ii. --- Transferability of plasmids --- p.33 / Chapter iii. --- Incompatibility --- p.34 / Chapter b. --- Molecular methods --- p.34 / Chapter i. --- Estimation of molecular size by agarose gel electrophoresis --- p.34 / Chapter ii. --- Plasmid fingerprinting --- p.35 / Chapter iii. --- Localization of resistance genes by DNA-DNA hybridization --- p.35 / Chapter 4. --- Ribotyping --- p.36 / Chapter 5. --- Total DNA fingerprinting --- p.37 / Chapter 6. --- Chromosomal insertion sequence IS200 profile analysis --- p.38 / Chapter 7. --- Others --- p.39 / Chapter a. --- Multilocus enzyme electrophoresis --- p.39 / Chapter b. --- Phenotype of lipopolysaccharide (LPS) --- p.39 / Chapter c. --- Envelope protein profiles and immunoblotting --- p.40 / Chapter I. --- Epidemiological typing of S. Typhi --- p.40 / Chapter J. --- Objectives --- p.46 / Chapter Chapter 2 --- Materials and Methods --- p.48 / Chapter A. --- Materials --- p.48 / Chapter I. --- Bacterial strains --- p.48 / Chapter II. --- Materials --- p.51 / Chapter B. --- Methods --- p.56 / Chapter I. --- Sensitivity testing --- p.56 / Chapter II. --- Characterization of plasmids --- p.58 / Chapter 1. --- Genetic studies --- p.58 / Chapter a. --- Transferability of resistance plasmids --- p.58 / Chapter b. --- Mobilization of resistances --- p.59 / Chapter c. --- Incompatibility grouping --- p.59 / Chapter 2. --- Molecular studies --- p.60 / Chapter a. --- Plasmid profile analysis --- p.60 / Chapter i. --- Plasmid extraction --- p.60 / Chapter ii. --- Agarose gel electrophoresis --- p.61 / Chapter b. --- Molecular characterization of plasmid --- p.61 / Chapter i. --- Extraction of purified plasmid DNA --- p.62 / Chapter ii. --- Restriction endonuclease digestion of plasmid DNA --- p.63 / Chapter III. --- Characterization β-lactamases --- p.63 / Chapter 1. --- Extraction of β-lactamases --- p.63 / Chapter 2. --- Determination of isoelectric points (pIs) --- p.64 / Chapter IV. --- Localization of resistance genes --- p.64 / Chapter 1. --- TEM-1 and TEM-2 genes --- p.65 / Chapter a. --- Oligonucleotide probes --- p.65 / Chapter b. --- Total DNA preparation --- p.66 / Chapter c. --- DNA-DNA-hybridization --- p.66 / Chapter i. --- Transfer of DNA to membrane filters --- p.66 / Chapter ii. --- Labelling of oligonucleotide probes (TEM-1 and TEM-2) --- p.67 / Chapter iii. --- Hybridization --- p.68 / Chapter 2. --- Chloramphenicol- and tetracycline-resistance genes --- p.69 / Chapter a. --- Preparation of probes --- p.69 / Chapter b. --- Hybridization --- p.73 / Chapter i. --- Transfer of DNA to membrane filters --- p.73 / Chapter ii. --- Labelling of chloramphenicol- and tetracycline- resistance probes --- p.73 / Chapter V. --- Epidemiological typing --- p.75 / Chapter 1. --- Ribotyping --- p.75 / Chapter 2. --- DNA fingerprinting --- p.77 / Chapter C. --- Plan for achieving objectives --- p.77 / Chapter Chapter 3 --- Results --- p.79 / Chapter A. --- Antimicrobial susceptibilities --- p.79 / Chapter B. --- Characterization of resistance plasmids --- p.83 / Chapter C. --- β-lactamases produced by ampicillin-resistant S. Typhi --- p.85 / Chapter D. --- Localization of resistance genes --- p.85 / Chapter E. --- Plasmid profile analysis --- p.87 / Chapter F. --- Plasmid fingerprinting --- p.90 / Chapter G. --- Ribotyping --- p.93 / Chapter H. --- Chromosomal DNA fingerprinting --- p.107 / Chapter I. --- "Correlation of PstI, ClaI and KpnI ribotypes and NarI, EcoRV and MluI chromosomal types" --- p.124 / Chapter J. --- Correlation of PstI ribotypes and NarI chromosomal types --- p.126 / Chapter K. --- Epidemiology of S. Typhi in Hong Kong --- p.129 / Chapter Chapter 4 --- Discussion --- p.131 / Chapter A. --- Antimicrobial susceptibilities --- p.131 / Chapter B. --- Characterization of resistances --- p.132 / Chapter C. --- Plasmid profile analysis --- p.135 / Chapter D. --- Epidemiological analysis of S. Typhi --- p.136 / Chapter E. --- Area for future research --- p.143 / References --- p.145 / Appendix --- p.161 / Chapter A. --- Buffer and Stock solutions --- p.161 / Chapter B. --- Epidemiological information of S. Typhi isolates --- p.167

by Ka-ming Pang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1990. / Bibliography: leaves 95-100. / Abstract --- p.i / Introduction --- p.1 / Literature review --- p.2 / Chapter 1. --- Mode of Respiration in Enteric Bacteria --- p.2 / Chapter 2. --- Nitrate Respiration --- p.4 / Chapter 3 . --- Biochemistry of Nitrate Reductase --- p.7 / Chapter 4 . --- Regulation of Nitrate Reductase --- p.8 / Chapter 5. --- Genetics and Regulation of chlC (nitrate Reductase) --- p.10 / Chapter 6. --- chlC in Salmonella typhimurium --- p.14 / Chapter 7. --- Purpose of study --- p.16 / Materials and Methods / Chapter 1 . --- Strains --- p.18 / Chapter 2. --- Media --- p.18 / Chapter 3 . --- Solution --- p.20 / Chapter 4. --- β-galactosidase assay --- p.23 / Chapter 5. --- Preparation of chromosome DNA --- p.24 / Chapter 6. --- Small scale plasmid preparation --- p.25 / Chapter 7. --- Large scale plasmid preparation --- p.26 / Chapter 8. --- Preparation of lambda DNA --- p.27 / Chapter 9. --- Preparation of M13 ssDNA for sequencing --- p.30 / Chapter 10. --- Digestion of DNA with restriction enzymes --- p.31 / Chapter 11 . --- Agarose gel electrophoresis --- p.31 / Chapter 12. --- Ligation --- p.31 / Chapter 13. --- Transformation --- p.32 / Chapter 14. --- Direct gel test and C-test of ssDNA of M13 clones --- p.34 / Chapter 15. --- DNA sequencing --- p.34 / Results / Chapter 1 . --- β-galactosidase assay of HSK1001 --- p.37 / Chapter 2. --- Preparation of HSK1001 DNA --- p.37 / Chapter 3. --- Sau3A partial digestion of HSK1001 chromosomal DNA --- p.37 / Chapter 4 . --- Ligation of HSK1001 DNA to lambda EMBL3 --- p.40 / Chapter 5. --- In vitro packaging and screening of lambda clones --- p.40 / Chapter 6. --- Restriction mapping of lambda clones --- p.43 / Chapter 6.1 --- Restriction mapping of HSK4001 to HSK4006 --- p.43 / Chapter 6.2 --- Orientation of Mu dA fusion clones --- p.43 / Chapter 7 . --- "Sub-cloning of SalI-HindIII fragments of HSK4002 HSK4003, HSK4005 and HSK4006 into pFZYl" --- p.66 / Chapter 8. --- Sub-cloning of 2.4 kb HindIII fragment of HSK4005 and HSK4006 into pFZY1 --- p.67 / Chapter 9. --- Sub-cloning of 2.4 kb HindIII fragment of HSK4006 into M13mpl9 --- p.67 / Chapter 10. --- Sub-cloning of 2.4 kb HindIII fragment of HSK4005 into M13mp19 --- p.69 / Chapter 11. --- Sub-cloning of 2.5 kb SalI-HindIII fragment of HSK4006 into M13mpl8 --- p.72 / Chapter 12. --- Sub-cloning of 2.2 kb SalI-HindIII fragment of HSK4005 into M13mp19 --- p.72 / Chapter 13. --- Complementation test of M13 clones --- p.74 / Chapter 14. --- Sub-cloning of 4.3 kb HindIII-EcoRI fragment and 3.8 kb EcoRI-BamHI fragments of HSK4006 into M13 mp18 and mp19 --- p.74 / Chapter 15. --- DNA sequences of M13 clones --- p.77 / Dicussion / Chapter 1 . --- Cloning of Mu dA operon fusion to EMBL3 vector --- p.88 / Chapter 2 . --- Sequences of SalI-HindIII fragments of HSK4005 to HSK4006 --- p.92 / Reference --- p.95

by Kwong-kwok Wong. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1987. / Bibliography: leaves 158-164.

by Yuen-Shan Chan. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1987. / Bibliography: leaves 142-150.

Higher risks of food-borne illness associated with increased consumption of poultry products make it necessary to identify potential sources of contamination and apply intervention strategies that will prevent or minimize the risk of contamination during processing. This study investigated the effects of chemical and natural decontamination treatments including sprayed application of acidified calcium sulfate (ACS) in combination with -polylysine (EPL), dry-rubbing kosher salt coating and molten paraffin wax dipping application on microbial populations of broiler carcasses and parts. Treatments were evaluated for their effectiveness in reducing the numbers of artificially inoculated rifampicin resistant Salmonella Typhimurium strain NVSL 95-1776 on the skin surface of bone-in chicken breasts. General model procedures were used to find statistical differences (P<0.05) and separation of means was done with least square means using SAS 9.1. Chemical interventions (ACS + EPL) caused an overall reduction of ~0.65 CFU/ml of rifampicin resistant Salmonella Typhimurium populations in inoculated chicken breasts. Similar reductions were observed in validation experiments in whole carcasses when compared to post-eviscerated control samples as well as post chilled treated samples when compared to post-chill controls. Kosher salt interventions caused ~1.15 CFU/ml log reductions in rifampicin resistant Salmonella Typhimurium loads. Significant differences (>2 log reductions) were also observed in validation trials in both pre- and post-chilled samples when compared to non-treated pre- and post-chilled controls. Only for psychrotrophic counts, chilled and post-chill interventions did not have a significant effect (P>0.05). The use of molten paraffin wax caused <0.51 CFU/ml log reductions on rifampicin resistant Salmonella Typhimurium in chicken breasts. In addition, drip loss on kosher treated samples was 53.8% lower than non-treated counterparts. However, kosher salt application caused a decrease in lightness (*L values) and yellowness (*b values) on treated carcasses when compared to controls, redness (*a values) were not significantly affected. Results indicate that the combined use of ACS and EPL at the stated conditions and the coating application of kosher salt on broiler carcasses significantly reduce pathogen contamination and microbial indicator loads, thus providing an alternative validated antimicrobial intervention for potential use by the poultry industry.

Higher risks of food-borne illness associated with increased consumption of poultry products make it necessary to identify potential sources of contamination and apply intervention strategies that will prevent or minimize the risk of contamination during processing. This study investigated the effects of chemical and natural decontamination treatments including sprayed application of acidified calcium sulfate (ACS) in combination with -polylysine (EPL), dry-rubbing kosher salt coating and molten paraffin wax dipping application on microbial populations of broiler carcasses and parts. Treatments were evaluated for their effectiveness in reducing the numbers of artificially inoculated rifampicin resistant Salmonella Typhimurium strain NVSL 95-1776 on the skin surface of bone-in chicken breasts. General model procedures were used to find statistical differences (P<0.05) and separation of means was done with least square means using SAS 9.1. Chemical interventions (ACS + EPL) caused an overall reduction of ~0.65 CFU/ml of rifampicin resistant Salmonella Typhimurium populations in inoculated chicken breasts. Similar reductions were observed in validation experiments in whole carcasses when compared to post-eviscerated control samples as well as post chilled treated samples when compared to post-chill controls. Kosher salt interventions caused ~1.15 CFU/ml log reductions in rifampicin resistant Salmonella Typhimurium loads. Significant differences (>2 log reductions) were also observed in validation trials in both pre- and post-chilled samples when compared to non-treated pre- and post-chilled controls. Only for psychrotrophic counts, chilled and post-chill interventions did not have a significant effect (P>0.05). The use of molten paraffin wax caused <0.51 CFU/ml log reductions on rifampicin resistant Salmonella Typhimurium in chicken breasts. In addition, drip loss on kosher treated samples was 53.8% lower than non-treated counterparts. However, kosher salt application caused a decrease in lightness (*L values) and yellowness (*b values) on treated carcasses when compared to controls, redness (*a values) were not significantly affected. Results indicate that the combined use of ACS and EPL at the stated conditions and the coating application of kosher salt on broiler carcasses significantly reduce pathogen contamination and microbial indicator loads, thus providing an alternative validated antimicrobial intervention for potential use by the poultry industry.

Food irradiation is costly in terms of the energy utilized and the time spent, therefore, it is imperative to optimize it in order to avoid sub lethal dose or an overdose both of which have detrimental effects on the quality of fresh produce such as cantaloupe. The bacterial load in fresh cut cantaloupe flesh was quantified on the basis of growth and mobility over time, and used as the basis for targeted irradiation simulation. The bacterial growth was predicted using the Gompertz model, while a power law function was used for predicting the bacterial mobility. The microbiological structure of cantaloupe flesh was assessed using Transmission Electron, Scanning Electron, and Light Microscopy as a basis for understanding the mobility of the bacteria into the internal mesocarp tissues. A plate assay was also undertaken to determine the possibility of S. typhimurium producing cell wall degrading enzymes such as polygalacturonase to gain access into intact fresh cantaloupe tissues. S. typhimurium in fresh cut cantaloupe flesh has a lag phase duration of 7.76 hours and can reach a maximum population of 7.98 logs CFU/g in 30 hours. Cantaloupe flesh has a vast network of intracellular spaces through which the bacteria can move into the internal mesocarp tissues, particularly because S. typhimurium (LT2) does not produce any enzymes such as polygalacturonase which could be breaking down the cell wall binding structures as a mechanism for internalization into intact internal tissues. A theoretical bacterial inactivation dose estimate based on the experimentally determined D10-value and the bacterial population was used to simulate irradiation treatment of the cantaloupe flesh samples using a 10MeV electron beam irradiator (LINAC) to establish the best treatment. The optimal 10 MeV electron beam irradiation treatment for S. typhimurium internalized in fresh cut cantaloupe samples for 30 hours was determined to be a double beam with 0.5 cm attenuation of Lucite (Trademark) at the top and 3.3 cm at the bottom.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 149-164). Available also in a digital version from Dissertation Abstracts.

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