Selective medium for isolation of Treponema hyodysenteriae

Abstract

Pure cultures of 6 pathogenic isolates of T. hyodysenteriae, the colonic mucosal scrapings of 7 pigs with acute swine dysentery, and feces from 7 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.degree. C in a vented GasPak jar with a cold Pd catalyst and 80:20 H2-CO2 by evacuation and refilling or a H2-CO2 generator envelope. Viable cell counts of the 6 pathogenic isolates were not altered by plating on TSA-S with 400 .mu.g of spectinomycin/ml (TSA-S400) compared with TSA alone. Dilutions of colonic mucosal scrapings from 7 pigs with acute swine dysentery showed unchanged numbers of T. hyodysenteriae 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 > 99.9%. Pathogenicity of T. hyodysenteriae was not altered by isolation or serial passage on TSA-S400.