In vitro antimicrobial susceptibility of Brachyspira hyodysenteriae strains isolated in Japan from 1985 to 2009.

The antimicrobial susceptibilities of 72 Brachyspira hyodysenteriae isolates collected from clinical cases of swine dysentery (SD) in 11 prefectures in Japan between 1985 and 2009 were investigated by an agar dilution method using five antimicrobial agents. There is a tendency of Japanese field isolates of B. hyodysenteriae to acquire resistance to the main antimicrobials used in SD treatment such as tiamulin, valnemulin, and efrotomycin. A responsible approach for selection and use of antimicrobial agents is required for SD treatment.