In vitro susceptibility of 21 antimicrobial agents to 37 isolates of Brachyspira hyodysenteriae isolated from pigs in Okinawa Prefecture.

The in vitro susceptibilities to 21 antimicrobial agents, of 37 isolates of Brachyspira (B.) hyodysenteriae isolated from pigs in Okinawa meat center and a pig farm in Okinawa Prefecture, Japan, were determined by the agar dilution method. Carbadox was the most active of all the agents tested against the isolates (MIC: <0.003 to 0.05). All the isolates were highly susceptible to olaquindox, tiamulin, dimetridazole, efrotomycin and valnemulin with MICs ranging from </=0.1 to 1.6 microg/ml. Penicillins, chloramphenicol, tetracyclines, terdecamycin and streptomycin were also active against the isolates. Most isolates were resistant to lincomycin, avilamycin and macrolides (with the exception of terdecamycin).