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Characterisation, pathogenicity and epidemiology of serpulina pilosicoli sp. nov. and other intestinal spirochaetes in pigs and humans

Trott, Darren John (1997) Characterisation, pathogenicity and epidemiology of serpulina pilosicoli sp. nov. and other intestinal spirochaetes in pigs and humans. PhD thesis, Murdoch University.

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A variety of weakly 8-haemolytic intestinal spirochaetes (WBIIlS) colonise the large intestine of humans and animals. Their potential role as disease-causing organisms is uncertain. In both pigs and humans, however, a group of WBIIlS has been associated with intestinal spirochaetosis (IS), a condition characterised by diarrhoea and the end-on attachment of spirochaetes to the colonic epithelium. The major aims of this thesis were to characterise this group of WBIIlS and determine their disease associations in various host species.

Phenotypic and genetic comparison with other spirochaetes in the genus Serpulina showed that the WBHIS associated with IS belonged to a new species, Serpulina pilosicoli sp. nov. Identifying pbenotypic characteristics of S. pilosicoli included their ultrastructural appearance, hydrolysis of hippurate, lack of 8-glucosidase activity and metabolism of D-ribose.

Serpulina pilosicoli strains isolated from pigs and humans colonised and induced diarrhoea, weight loss and attachment in orally-inoculated day-old SPF chicks. Variation in the degree of pathogen ic change was observed amongst the four human strains and two porcine strains tested. The non-pathogenic WBIIlS species Serpulina innocens, Serpulina murdochii and Brachyspira aalborgi failed to colonise the chicks. Both porcine and human S. pilosicoli strains also induced diarrhoea and colitis with crypt abscessation, attachment and local invasion in orally inoculated newly-weaned pigs.

Multilocus enzyme electrophoresis (MLEE) was used to identify strains of S. pilosicoli from the faeces of dogs and birds. All human intestinal spirochaetes tested, including seven isolates from the blood of debilitated patients, were confirmed as S. pilosicoli. The population structure of S. pilosicoli was shown to be panmictic, in contrast to the epidemic population structure of Serpulina hyodysenteriae (the agent of swine dysentery). This suggests that recombination is important in the generation of genetic variation in the genus Serpulina.

Villagers in the Highlands of Papua New Guinea had a high rate of colonisation with S. pilosicoli (22.8%) compared with those living in an urban environment (9.5%) and non-indigenous humans (0%). Only village dogs (5.3%) represented a significant risk of zoonotic transmission with some strains having the same MLEE and pulsed-field gel electrophoresis pattern as several human strains. The annual incidence of human infection was calculated as 93.6%, with an average duration of 117 days. S. pilosicoli may be an important, newly-recognised pathogen of both animals and humans.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): Division of Veterinary and Biomedical Sciences
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 and Robertson, Ian
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