Purification, characterization, and serologic characteristics of Bacteroides nodosus pili and use of a purified pili vaccine in sheep.

Hair-like appendages (pili) were isolated and purified from Bacteroides nodosus, the etiologic agent of foot rot disease in sheep. Microscopic and biochemical analyses indicated that pili from organisms isolated in Australia, New Zealand, and the United States are morphologically and structurally similar. Pili are filamentous assemblies of identical protein subunits. Using specific antisera raised in rabbits against pili, 7 antigenic types were identified. A geographic pattern in the distribution of the pilus serotypes was not evident. In a preliminary vaccine trial, sheep vaccinated with purified pili developed resistance to challenge exposure to B nodosus. Protection was correlated positively with the serum anti-pilus antibody titers.