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Detection, subspecific differentation and epidemiology of Serpulina hyodysenteriae

Combs, Barry George (1995) Detection, subspecific differentation and epidemiology of Serpulina hyodysenteriae. PhD thesis, Murdoch University.

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Serpulina hyodysenteriae is the aetiological agent of swine dysentery, an important disease of pigs worldwide. Control measures have been hampered by difficulties in diagnosis, and limited knowledge of the epidemiology of the infection. In this study, DNA-based techniques were developed for use in addressing these problems.

Whole chromosomal DNA probes were used to identify S. hyodysenteriae isolates. In dot-blot hybridisation, their sensitivity ranged from 84.6 to 100%, and their specificity from 71.4 to 92.3%. A recombinant DNA probe of 1.7 kb was subsequently developed and shown to have both a sensitivity and specificity of 100%; it also detected 10 ng of S. hyodysenteriae DNA, 1 x 106 purified cells, and 2.5 x 107 cells per gram of pig faeces. This was improved to 1 x 103 to 1 x 104 cells by growing seeded faeces on solid medium, and then hybridising the probe with DNA extracted from the total bacterial growth. The 1.7 kb probe DNA was partially sequenced, and a polymerase chain reaction technique developed to amplify a 288 bp fragment. One ng of DNA and 1 x 103 S. hyodysenteriae cells could be detected using this method.

The distribution and epidemiology of S. hyodysenteriae in Australia was investigated, by using serogrouping, DNA restriction endonuclease analysis (REA), and restriction fragment length polymorphism analysis (RFLP) to type 136 isolates from 83 properties. These isolates belonged to eight serogroups, the most common of which were B and D, found on 37 and 27 properties respectively. The isolates were divided into nine major REA patterns, and 45 minor patterns. Twenty of the 45 patterns were shared between properties, but the transmission of SD between piggeries appeared more common within states than between states. REA typing was used to confirm that the introduction of pigs to piggeries was the source of SD in four separate outbreaks, and to show that rats were an ongoing source of infection for pigs on another property. Isolates with the same major REA pattern generally had the same RFLP group supporting the view that the nine major REA patterns were clonal groups. RFLP typing was not as discriminatory for identifying specific strains as REA , but it was useful for determining genetic relatedness between isolates.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary Studies
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Hampson, David
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