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Doctoral thesis2014Open access

Treponema spp. in necrotic skin ulcers in pigs : phenotypic and genetic features

Svartström, Olov

Abstract

Treponema belongs to the phylum Spirochaetes consisting of bacteria distinguishable by a unique cell architecture that enables corkscrew-like motility. In two case studies, treponemes were isolated from ear necrosis and shoulder ulcers, two types of skin lesions that have impact on animal welfare and may cause economic losses. This doctoral thesis focuses on a hypothesis that Treponema spp. have a pathogenic role in the progression of ear necrosis and shoulder ulcers in pigs and, as Treponema spp. are present in gingiva of pigs, that transmission to skin is mediated by biting or licking. The thesis describes their occurrence, phenotypic and genetic features. We sampled 109 pigs with lesions and 60 apparently healthy piglets. Spirochetes were present in 73% of the shoulder ulcers, in 53% of the ear necroses and in 9.7% of the gingivae. Many identified phylotypes were similar to Treponema spp. considered as pathogens in bovine digital dermatitis, a claw disease in cattle. Similar phylotypes were present both in gingiva and ulcers. There were indications of transmission between gingiva and ulcers. Twelve isolates were acquired and identified as T. pedis, T. parvum and T. sp. OMZ840-like. Metabolic patterns were similar to those of other treponemes and were not discriminatory between isolates. All except two gingival isolates showed unique DNA fingerprints. Treponema sp. OMZ840-like and T. pedis isolates were hemolytic, T. parvum was not. The isolates were generally susceptible to the tested antimicrobials. The genome sequence of T. pedis strain T A4 from ear necrosis was de novo assembled and analyzed. The genome was most similar to that of T. denticola, a species strongly associated with human periodontitis. Several of the predicted genes in T. pedis were homologous to virulence related genes in T. denticola, including those encoding the major surface sheath protein, dentilisin and dentipain. In T. denticola, IdeT is a protein that includes the oligopeptidase domain dentipain. An IdeT-homologue in T. pedis strain T A4, TPE0673, was recombinantly expressed in Escherichia coli and purified for in vitro testing. TPE0673 did not display protease activity towards immunoglobulin G (IgG) or insulin as its homologues. However, western blot analysis showed that IgG in serum from sows with shoulder ulcers bound to purified TPE0673, suggesting an immunogenic property of this gene. In conclusion, this thesis describes an association between Treponema spp. with ear necrosis and shoulder ulcers. The treponemes present in pig ulcers were phylogenetically similar to those of oral origin and transmission between gingiva and ulcer was indicated. Finally, analysis of the genome of T. pedis revealed the presence of several putative virulence genes indicating a pathogenic potential for this species.

Keywords

Treponema pedis; Spirochetes; Shoulder ulcers; Ear necrosis; Pigs; Treponema sp. OMZ840; Treponema parvum

Published in

Acta Universitatis Agriculturae Sueciae
2014, number: 2014:38ISBN: 978-91-576-8024-2, eISBN: 978-91-576-8025-9
Publisher: Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Microbiology
    Bioinformatics and Systems Biology

    Permanent link to this page (URI)

    https://res.slu.se/id/publ/53231