Serological response to Pasteurella multocida NanH sialidase in persistently colonized rabbits.

Pasteurella multocida is a mucosal pathogen that colonizes the upper respiratory system of rabbits. Respiratory infections can result, but the bacteria can also invade the circulatory system, producing abscesses or septicemia. P. multocida produces extracellular sialidase activity, which is believed to augment colonization of the respiratory tract and the production of lesions in an active infection. Previously, it was demonstrated that some isolates of P. multocida contain two unique sialidase genes, nanH and nanB, that encode enzymes with different substrate specificities (S. Mizan, A. D. Henk, A. Stallings, M. Meier, J. J. Maurer, and M. D. Lee, J. Bacteriol. 182:6874-6883, 2000). We developed a recombinant antigen enzyme-linked immunosorbent assay (ELISA) based on the NanH sialidase of P. multocida and demonstrated that rabbits that were experimentally colonized with P. multocida produce detectable anti-NanH immunoglobulin M (IgM) and IgG in serum, although they demonstrated no clinical signs of pasteurellosis. In addition, clinically ill pet rabbits infected with P. multocida possessed IgM and/or IgG antibody against NanH. The NanH ELISA may be useful for the diagnosis of P. multocida infections in sick rabbits as well as for screening for carriers in research rabbit colonies.