Identification of Treponema hyodysenteriae by a rapid slide agglutination test

A rapid slide agglutination (SA) test was developed to identify the spirochaete Treponema hyodysenteriae, the causative organism of swine dysentery. The specificity of the antiserum was increased by a single absorption with two intestinal spirochaetes. Using this test, it was possible to identify 30 out of 31 spirochaetes which were beta-haemolytic and gave a positive reaction in growth inhibition (GI) tests with T hyodysenteriae antiserum. All except one of these spirochaetes were isolated from herds with a history of swine dysentery or suspected swine dysentery. The majority of the spirochaetes gave a rapid, strongly, positive reaction in the SA test but seven strains, although recognisably positive, reacted more weakly. Of 28 other spirochaetes which were weakly beta-haemolytic and did not react in GI tests with T hyodysenteriae antiserum, 27 were negative in the SA test. The remaining strain was autoagglutinable and thus could not be identified. The indole test correlated less well with the results of SA and GI tests. All 31 strains which were identified as T hyodysenteriae produced indole, but so did nine of the 28 other spirochaetes. The slide agglutination test is a potentially useful method for rapid identification of T hyodysenteriae.