brachyspira hyodysenteriae brachyspira hyodysenteriae brachyspira hyodysenteriae, formerly serpulina hyodysenteriae and other binomial names, is a gram-negative anaerobic spirochete species of bacteria. it is the causative agent of swine dysentery. brachyspira hyodysenteriae scientific classification domain: bacteria phylum: spirochaetota class: spirochaetia order: spirochaetales family: sarpulinaceae genus: serpulina binomial name serpulina hyodysenteriaeharris et al. 1972 synonyms brachyspira hyodysenteriae treponema hyodysenteriae