Prevalence of Serpulina species in relation to diarrhea and feed medication in pig-rearing herds in Sweden

Abstract

Objective - To determine prevalence of various phenoand genotypes of Serpulina sp in young pigs in relation to diarrhea and feed medication in Swedish pig-rearing herds. Design - Isolation of spirochetes. Phenotypical and genotypical classification. Sample Population - Young pigs (n = 358) in 19 pig-rearing herds. Procedure - Serpulina isolates were classified according to a biochemical scheme based on hemolysis, indole production, hippurate hydrolysis, and α-galactosidase, α-glucosidase, and β-glucosidase activities. The 16S rRNA sequences for 10 of the field strains and 2 type strains of Serpulina spp were aligned and compared. Minimum inhibitory concentrations of olaquindox for 9 of the strains were determined. Results - Weakly β-hemolytic intestinal spirochetes (WBHIS) were isolated from 17 of the herds and 65% of the samples. More than 1 phenotype of WBHIS was found in 12 of the 19 herds. S hyodysenteriae was not isolated in any of the herds. Hippurate-positive WBHIS were isolated in 6 of 7 herds affected by diarrhea, but in only 1 of 8 herds without diarrhea. Hippurate-positive strains were closely related to the pathogenic strain P43 if judged from sequence comparisons. Strains with the same biochemical profile isolated within a herd had identical sequences, but when isolated from different herds, sequence differences were observed. The prevalence of WBHIS was reduced in herds medicated with olaquindox. Investigated field strains had minimum inhibitory concentration values ≤ 1 μg/ml for olaquindox. Conclusion - The presence of WBHIS, with the ability to hydrolyze hippurate, was related to diarrhea in pig herds. Clinical Relevance - Potentially pathogenic WBHIS can be distinguished from nonpathogenic strains by the hippurate hydrolysis test.