Laboratory identification and enteropathogenicity testing of Serpulina pilosicoli associated with porcine colonic spirochetosis.

Pathogenic intestinal spirochetes of swine include Serpulina hyodysenteriae, a strongly beta-hemolytic spirochete that causes swine dysentery, and S. pilosicoli, a weakly beta-hemolytic intestinal spirochete (WBHIS) that causes porcine colonic spirochetosis. Because of the existence of nonpathogenic WBHIS in the normal swine colon, it is important to develop laboratory procedures for accurate identification of S. pilosicoli. The purpose of the present study was to assess hippurate hydrolysis and polymerase chain reaction (PCR) amplification of specific 16S ribosomal RNA (rRNA) sequences for identification of porcine S. pilosicoli. Additionally, the enteropathogenicity of 8 field isolates of porcine S. pilosicoli was determined by challenge exposure of 1-day-old chicks and sequential histologic examination of the cecal mucosa. The field isolates of porcine S. pilosicoli hydrolyzed hippurate and yielded S. pilosicoli-specific products by PCR amplification of 16S rRNA sequences. Although all of the field isolates of porcine S. pilosicoli attached to the cecal epithelium of challenge-exposed chicks by day 21 postinoculation, some isolates had locally invasive phenotypes. We concluded that identification of porcine S. pilosicoli could be made on the basis of results of hippurate hydrolysis and 16S rRNA PCR amplification. Challenge inoculation of 1-day-old chicks followed by histologic examination of the cecal mucosa demonstrated the enteropathogenicity of porcine S. pilosicoli.