Phenotypic classification, detection and phylogeny of Serpulina species in swine.
1996
Fellstroem C.
Swine dysentery (SD) and spirochetal diarrhea are important and universal diarrheal diseases affecting pigs, both caused by Serpulina spp. In this work, a biochemical classification scheme for spirochetes of the genus Serpulina, was elaborated. The scheme consists of six groups: I, II, IIIa, IIIb, IIIc and IV. Characteristic features of the group I spirochetes are strong hemolysis, indole production and lack of alfa-galactosidase activity. Group II spirochetes differ from group I by virtue of their weak hemolysis. Group III spirochetes are characterized by weak hemolysis, beta-glucosidase activity and lack of indole production and the spirochetes of group IV, by virtue of their hippurate hydrolysis capacity and lack of beta-glucosidase activity. The 16S rRNA genes from 26 isolates, representing all the proposed biochemical groups, were sequenced. Sequence analysis revealed a relationship between phenotype and genotype for four of the proposed groups. A large number of unique positions for group IV spirochetes was found, which is why they should probably be assigned to as a separate species. A phylogeny based on 16S rRNA sequences of the genus Serpulina is presented. Epidemiological relations of the weakly beta-hemolytic intestinal spirochetes (WBHIS) were studied in Swedish pig-rearing herds. All 19 herds investigated proved negative regarding isolation of Serpulina hyodysenteriae, though WBHIS were isolated from 17 of them. More than one phenotype of WBHIS was isolated from most of the herds studied. A relationship between herds with diarrheal disorders and the isolation of group IV spirochetes was demonstrated. Sequence analysis of the 16S rRNA gene showed almost 100% identity between isolated group IV strains and the type strain of spirochetal diarrhea, P43. Shedding of WBHIS was significantly less common in herds where olaquindox was administered in the daily feed. A PCR assay for group IV spirochetes was presented and utilized on type strains and field isolates of Serpulina from Sweden, Denmark, Scotland and Belgium. The results of this assay were consistent with those of the biochemical tests. Group IV isolates were identified from all countries included. A diagnostic scheme from the genus Serpulina, based on three rapid and easily performed biochemical tests, is proposed.
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