Commercial herbs, spices and their essential oils from Libya were examined for their toxicological and antilisterial properties. In order to achieve this, 153 samples of milk and dairy products were examined for the isolation of L. monocytogenes and other Listeria spp. and also for their general microbiological qualities. The latter were found to conform to European and American microbiological specifications. Listeria monocytogenes was not isolated from any of the products, but isolated from swabs of the floor of a Glasgow dairy factory and they were identified as serotypes 1I2b and 4b. However, L. seeligeri and L. grayi were isolated from ice cream samples at (0.7 % of the total products). Studies on the growth and survival conditions (salt concentration, pH, temperature and atmospheres) of the isolates and 5 typed cultures of L. monocytogenes varied. The susceptibilities of L. monocytogenes to gentamicin (30 Jlglml) , kanamycin (25 Jlglrnl) , penicillin G (30 Jlglml) , tetracycline (25 Jlglrnl) , streptomycin (10 units), ampicillin (10 units) and erythromycin «0.005-1.0Jlglml); the susceptibilities were within the range of the breakpoints of Minimum Inhibitory Concentration (MIC). The MIC ranged from <0.005 to 148 Jlglml for all the antibiotics tested. The susceptibilities of L. monocytogenes to probiotic bacteria included B. bifidum 0795, B. breve NCIMB 2258, B. adolescentis NCIMB 2204, Lb. bulgaricus NCFB 1489 and Lb. plantarum DSM 12028 were 100, 57, 34, 34 and 28% respectively. However, the susceptibilities of L. seeligeri and L. grayi to B. adolescentis NCIMB 2204, B. breve NCIMB 2258, B. bifidum 0795, Lb. plantarum DSM 12028, Lb. bulgaricus NCFB 1489 and Lb. acidolescentis NCIMB 2204 were 100,100, 100, 50, 50 and 50 % respectively. The antilisterial activity of the water extracts was lower than the essential oils. The MIC value of clove, mustard green and black seed oils were < 0.01 - 1.1, 0.019 - 0.43 and 0.09 - 0.85 Jlglml respectively and 625.00 Jlglml for cinnamon and thyme oils. In contrast, garlic, coriander, mustard seed, castor and red chili oils had no antilisterial activity against L. monocytogenes, L. seeligeri and L. grayi. However, chili oils in diethyl ether had antilisterial activity against L. monocytogenes, L. seeligeri and L. grayi. The cytotoxic effects of the essential oils showed that the MIC of clove oil was less than the inhibition concentrations of 50% (lCso) listerolycin 0 (LLO) which affected L. monocytogenes isolates, but did not have any effect on the cell lines used (Vero and Hep_2
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:547425 |
| Date | January 2012 |
| Creators | Ben-Mohamed, Najat Sharef A. |
| Publisher | Glasgow Caledonian University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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