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Title of Thesis

Institute/University/Department Details
University f Karachi/ Department of Microbiology
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
lipids, listeria, l. monocytogenes, ld50, listeriosis, leukocyte count

Virulent and avirulent species of Listeria were studied and characterized on the basis of their morphological, cultural and biochemical characters. In addition CAMP test was also performed for species differentiation. The growth of L. monocytogenes NCTC 7973 on TSB and TPB incubated at different temperatures was investigated. The maximum production of biomass was observed in TSB medium at 20ºC or 4ºC. However, low temperature substantially reduced the growth response in both the media. The LD50 of Listeria species was determined in white mice by intraperitoneal route and was found to be between 0.544X105 -2.01X108. Animal passage modestly enhanced the virulence of L. monocytogenes NCTC 7973, as indicated by the lower LD50 value for passaged culture then unpassaged culture. This study further addresses above findings, in details, utilizing histopathological studies to portray the lesions pathogenesis with the help of microscopy

5-7.8% (dry weight) of lipid was yielded in different Listeria species depending upon the degree of virulence of the species. The cellular fatty acid composition determined by gas chromatography-mass spectrometry, was found not to differ among L. monocytogenes NCTC 7973, L. ivanovii SLCC 7842, L. seeligeri SLCC 3954 by far the most common members are C15 and C16 chain length fatty acids. This pattern is rather similar in all species, whereas C19 and C22 carbon chain fatty acid is characteristic of lipid present in L. monocytogenes. At low temperature, L. monocytogenes is able to change the relative composition, which could increase the fluidity of the bacterial memberane. A key player in this connection is anteiso C15 fatty acid as more C15 fatty acid is produced at low temperature

A marked monocytic reaction was after the injection of virulent L. monocytogenes, partly virulent L. ivanovii. There was no change after injection of L. seeligeri. Monocytosis producing activity is present not only in L. monocytogenes cells (live/killed) but was also present in lipid. On further fractionation of lipid by vacuum liquid chromatography the active fractions were found to contain high numbered carbon chain fatty acids along with the phosphorus, protein and carbohydrate

The listerial lipids significantly increased mouse resistance toward the Listeria infection. Killed L. monocytogenes cells as well as their lipids exhibit a very high adjuvant activity. Experiments conducted for determining the effect of sustained monocytosis on serum antibody levels, suggests an association between monocytes and humeral immune response. MPA was also found to be present in saline extractable material (SE) from L. monocytogenes. The minimum dose of SE capable of producing a monocytosis was 50 mg/kg but it was found to be non-toxic when tested on Aretemia salina leach larvae

Both MPA and immunostimulating activity were readily extracted with aqueous solvents and found as two interdependent activities by high performance liquid chromatography. As low as 50 mg/kg of the SE fractions SE-A and SE-C caused an elevation in the level of circulating monocytes and was found to be an effective promoter of immune response as indicated by the high serum antibody titre in mice and rabbits. Chemical analysis of SE and its active fractions showed the presence of phosphorus, carbohydrate and trace amount of protein Furthermore SE and its fractions were found to stimulate the cell mediated and humoral components of the immune system in experimental animals. SE and its active fraction elucidated a dose-related increase in SRBC, induced by 4 hours (early) and 24 hours (delayed) hypersensitivity reactions in rats

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S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents 0
264.79 KB
2 1 Introduction 1
58.12 KB
3 2 Review Of Literature 6
391.5 KB
  2.1 Classification 6
  2.2 History 7
  2.3 General Characteristies 7
  2.4 Listeria A Unique Microorganism 10
  2.5 Presence And Persistence 12
  2.6 Isolation And Identification 15
  2.7 Epidemiology 19
  2.8 Outbreaks Of Listeriosis And Association With Foods 21
  2.9 Seasonality Of Human And Listeriosis 22
  2.10 Control Of Listeriosis 23
  2.11 Disease Characteristics Of Listeria 29
  2.12 Transmission To Humans 33
  2.13 Products Of Biological Importance 34
  2.14 Lipid Content Of Listeria 40
4 3 Materials And Methods 42
436.31 KB
  3.1 Culters 42
  3.2 Identification And Characterization Studies 42
  3.3 Biomass Production 47
  3.4 Virulence And Toxicity Determination 49
  3.5 Brine Shrimp Bioassay 57
  3.6 Biochemical Studies 58
  3.7 Fractionation Of Crude Lipid Extract 65
  3.8 Saline Extraction (Se) Of L. Monocytogenes Nctc 7973 Delipidated Cells 68
  3.9 Biossays 72
  3.10 Preparation Of Sample Of Bioassays 74
  3.11 Differential Leukocyte Count ( Dlc ) 75
  3.12 Determining The Effect Of Live And Killed Listeria Species On Dlc 75
  3.13 Determining The Effect Of Crude Lipid Extract/Fractions Of Lipid Extract On Peripheral Blood Monocyte Number ( Pbmn ) 76
  3.14 Determining The Effect Of Crude Bacterial Lipids On The Course Of Experimental Listeria Infection In Mice 78
  3.15 Determining The Serum Antibody Titre Under Sustained Monocytosis (Against Live And Killed) Listeria Species In Experimentally Infected Rabbits 78
  3.16 Determining The Monocyte Producing Ability ( Mpa ) Of Crude Saline Extract And Fractions Separated By Hplc 82
  3.17 Immunodulatory Properties Of Saline Extract 82
  3.18 Determining The Effect Of Saline Extract On Cellular Response 84
  3.19 Statistical Analysis 85
5 4 Results 86
989.73 KB
  4.1 Morphological And Cultural Characteristics 86
  4.2 Biochemical Characteristics 90
  4.3 Factors Affecting Production Of Biomass 90
  4.4 Virulence And Toxicity 94
  4.5 Analysis Of Crude Lipid Extract ( Clc ) 120
  4.6 Analysis Of Crude Saline Extract (Se) And Fractions Separated By High Pressure Lipid Chromatography ( Hplc ) 131
  4.7 Effect Of Live And Killed Listeria Species On Differential Leukocyte Count ( Dlc ) 131
  4.8 Effect Of Crude Lipid And Lipid Fractions On Peripheral Blood Monocyte Number ( Pbmn ) 139
  4.9 Effect Of Listeria Species (Live And Killed) On Serum Antibody Response Under Sustained Monocytosis 150
  4.10 Effect Of Crude Listerial Lipids On The Course Of Listeria Infaction In Mice 158
  4.11 Effect Of Trypsin 158
  4.12 Effect Of Saline Extract (Se) Its Fractions On Peripheral Blood Monocyte Number 160
  4.13 Effect Of Saline Extract On Humoral Response 160
  4.14 Effect Of Saline Extract On Brine Shrimp 166
  4.15 Hypersensitivity Reactions 166
6 5 Discussion 169
234.88 KB
  5.1 Morphological, Cultural And Biochemical Characters 169
  5.2 Factors Affecting Production Of Biomass 170
  5.3 Toxicity Study 171
  5.4 Listerial Lipid 174
  5.5 Effect Of Media And Temperature On Lipid Production 175
  5.6 Composition Of Fatty Acids And Their Dependence On Temperature 176
  5.7 Monocytosis Producing Ability/Activity ( Mpa ) 178
  5.8 Effect Of Crude Lipids On The Course Of Listeria Infection 181
  5.9 Bioassay Of Saline Extract And Hplc Fractions 184
7 6 References 190
531.63 KB