Comparison of stained smears and culturing for identification of Treponema hyodysenteriae.

A comparative study was made of stained fecal smears and cultured fecal swabs for identification of the large spirochetes Treponema hyodysenteriae and Treponema innocens. Feces were obtained by swabbing rectums, colons, and stools of nonexposed swine and swine experimentally exposed to swine dysentery. In this study there was a significant (P less than 0.001) correlation between the observation of one or more large spirochetes on stained slides and obtaining either a strong or a weak beta-hemolytic reaction in culture. A significant (P less than 0.001) correlation was also found between the observation of one or more large spirochetes on stained smears or obtaining either a strong or a weak beta-hemolytic reaction in culture and the occurrence of either nonhemorrhagic or hemorrhagic diarrhea in the swine. In the diarrheic swine at the time of swabbing, 157 of 393 samples (40%) were negative for both the presence of large spirochetes on stained smears and the production of either a strong or a weak beta-hemolytic reaction; in nondiarrheic swine, 42 of 278 samples (15.1%) were positive in stained smears and 32 of 268 samples (11.9%) were positive by culturing. In swine infected with swine dysentery, 17 of 1,011 samples produced weak beta-hemolytic reactions, and in swine infected with nonpathogenic large spirochetes of T. innocens, three of 34 samples produced strong beta-hemolytic reactions. It was concluded from this study that neither staining rectal smears nor culturing rectal swabs is sufficient, either together or alone, for the diagnosis of swine dysentery; however, these laboratory methods could be highly supportive of a diagnosis of swine dysentery in swine with clinical signs and lesions of the disease.