Cryptic plasmids ranging from 2.0 to 10C kb in size were isolated from 25 out of 122 Listeria monocytogenes strains, and from 7 out of 11 strains of other Listeria species. / Of 2500 clones of a genomic library of L. monocytogenes 81-861 generated in Escherichia coli cells, 5 clones were identified in which $ beta$-hemolytic activity was stably expressed. Testing by intraperitoneal injection showed that these clones were lethal to mice. Restriction mapping of the inserts of the recombinant plasmids showed that, apart from a 650-bp internal Hind III fragment in 2 inserts, there were no other common sites. No homology was demonstrated between the DNAs of the inserts when Southern blots of restriction digests of the 5 plasmids were probed, though homology was demonstrated between the L. monocytogenes listeriolysin O gene and the DNA of one insert. The evidence suggests that at least one additional $ beta$-hemolysin, other than listeriolysin O, exists in this strain of L. monocytogenes, and that it may be a virulence factor. / Using a direct colony hybridization procedure on hydrophobic grid-membrane filters (HGMFs), the inserts of the recombinant plasmids were screened, and a DNA probe specific for L. monocytogenes was identified. After labelling with horseradish peroxidase and colour development of the chromogen, a commercial counter (HGMF Interpreter) was able to detect and count the organism electronically. When the efficacy of the chromogen-labelled DNA probe method on HGMFs was compared with the conventional method for three artificially-inoculated foods, there were no significant differences ($ alpha$ = 0.05) shown in the recovery of L. monocytogenes from the foods.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.70314 |
| Date | January 1991 |
| Creators | Peterkin, Pearl I. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Microbiology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001276583, proquestno: AAINN74765, Theses scanned by UMI/ProQuest. |
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