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