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CHEMICAL AND BIOLOGICAL STUDIES ON LIPIDS OF LISTERIA SPECIES

Hany, Omm-E- (1989) CHEMICAL AND BIOLOGICAL STUDIES ON LIPIDS OF LISTERIA SPECIES. PhD thesis, University of Karachi, Karachi.

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Abstract

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

Item Type:Thesis (PhD)
Uncontrolled Keywords:lipids, listeria, l. monocytogenes, ld50, listeriosis, leukocyte count
Subjects:Biological & Medical Sciences (c) > Biological Sciences(c1) > Microbiology(c1.8)
ID Code:1288
Deposited By:Mr. Muhammad Asif
Deposited On:27 Jan 2007
Last Modified:04 Oct 2007 21:05

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