Brachyspira

Brachyspira is a genus of anaerobic, spiral-shaped bacteria in the family Brachyspiraceae, order Spirochaetales. Like other spirochetes, they possess periplasmic flagella (axial filaments) that give them a characteristic corkscrew motion. They are typically Gram-negative or Gram-variable and are adapted to colonize the lower digestive tract of vertebrates.

Species within the genus are found in the distal large intestine of various mammals and birds. The best known pathogenic members include Brachyspira hyodysenteriae, which causes swine dysentery in pigs, and Brachyspira pilosicoli, as well as Brachyspira aalborgi, which are associated with intestinal spirochetosis in humans and other hosts. Other species such as B. murdochii and B. innocens are reported in animals and may have lower virulence or act as commensals.

Disease manifestations vary by species and host. B. hyodysenteriae typically induces mucohemorrhagic diarrhea, with poor weight gain and ill thrift in pigs. B. pilosicoli and B. aalborgi can colonize the mucosal surface of the colon and are linked to intestinal spirochetosis, which can be asymptomatic or associated with chronic diarrhea and abdominal discomfort in humans.

Diagnosis relies on culture under anaerobic conditions on enriched media, supplemented by molecular methods (PCR) or histopathology demonstrating spirochetes attached to the mucosal surface. Diagnosis may be challenging due to slow growth and fastidious requirements.

Treatment and control strategies depend on the species and host. In pigs, pleuromutilin antibiotics such as tiamulin or valnemulin are commonly used, alongside management and biosecurity measures. In humans, reported treatments include antibiotics such as metronidazole or doxycycline, with selection guided by susceptibility and clinical presentation. Preventive measures focus on hygiene, sanitation, and minimizing fecal-oral transmission.