Detection and enumeration of toxin-producing Pasteurella multocida with a colony-blot assay.

Colonies of toxin-producing Pasteurella multocida were detected with peroxidase-labeled monoclonal antibodies by a membrane assay. Examination of the specificity of the assay with 29 P. multocida cultures representing various geographic origins, hosts, and serotypes indicated that the test was specific for toxin-producing strains. No cross-reactions were observed with Bordetella species that can be associated with P. multocida in producing diseases in animals. A single membrane could be used to assay several isolated strains for toxin production or to enumerate toxin-producing colonies in mixed cultures. Toxin-producing P. multocida colonies were detected in primary cultures; hence, the assay appears to have good potential for widespread application with clinical samples.