Improved selective medium for the isolation of Treponema hyodysenteriae.

An agar medium with improved selection for Treponema hyodysenteriae was developed. Cultures of T. hyodysenteriae and T. innocens, feces from 11 clinically normal pigs, and colonic contents from 6 pigs with gross lesions consistent with swine dysentery were diluted in phosphate-buffered saline and plated on Trypticase soy agar (BBL Microbiology Systems, Cockeysville, Md.) with 5% citrated bovine blood (TSA), TSA with 400 micrograms of spectinomycin per ml (TSA-S400), TSA-S400 with 25 micrograms each of colistin and vancomycin per ml, and TSA with 5% pig feces extract and five antimicrobial agents (spiramycin, rifampin, vancomycin, colistin, and spectinomycin) (BJ). Viable numbers of T. hydodysenteriae grown on BJ were virtually identical to those for TSA, TSA-S400, and TSA-S400 with colistin and vancomycin. Pure cultures of four isolates of T. hyodysenteriae and three isolates of T. innocens were sustained through six subcultures on BJ. Fecal floras were completely inhibited on BJ for 14 of 17 fecal samples from both groups of pigs. A total of 461 colonic specimens from naturally occurring cases of porcine intestinal disease were plated on TSA-S400 and BJ. T. hyodysenteriae was isolated on both TSA-S400 and BJ for 69 specimens and on BJ alone for an additional 19 specimens.