Pure cultures of six pathogenic isolates of Treponema hyodysenteriae, the colonic mucosal scrapings of seven pigs with acute swine dysentery, and feces from seven unaffected pigs were diluted in phosphate-buffered saline and plated on Trypticase soy agar with 5% citrated bovine blood (TSA) and TSA with various levels of spectinomycin (TSA-S). The plates were incubated at 42 degrees C in a vented GasPak jar with a cold palladium catalyst and either 80:20 H2-CO2 by evacuation and refilling or a H2-CO2 generator envelope. Viable cell counts of the six pathogenic isolates were not altered by plating on TSA-S with 400 mug of spectinomycin per ml (TSA-S400) as compared with TSA alone. Dilutions of colonic mucosal scrapings from seven pigs with acute swine dysentery showed numbers of T. hyodysenteriae to be unchanged when plated on TSA-S400. Flora other than T. hyodysenteriae present in acute swine dysentery was inhibited, on the average, by 99.99%. Plating of dilutions of feces of unaffected pigs on TSA-S400 showed inhibition of flora that averaged more than 99.9%. Pathogenicity of T. hyodysenteriae was not altered by isolation or serial passage on TSA-S400.
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