SEROLOGICAL CHARACTERIZATION OF ACTINOBACILLUS-PLEUROPNEUMONIAE BIOTYPE-1 STRAINS ANTIGENICALLY RELATED TO BOTH SEROTYPE-2 AND SEROTYPE-7

Nine Danish Actinobacillus pleuropneumoniae biotype 1 isolates were sh own by latex agglutination and indirect haemagglutination to possess c apsular polysaccharide epitopes identical to those of serotype 2 strai n 1536 (reference strain of serotype 2) and strain 4226 (Danish seroty pe 2 strain). Immunodiffusion confirmed the antigenic relationship wit h serotype 2 and further demonstrated an antigenic relationship with s train WF83 (reference strain of serotype 7). SDS-PAGE with LPS from st rains 1536, 4226, WF83 and strain 7317 (representative of the 9 isolat es examined) showed that strains WF83 and 7317 had an identical smooth ladder pattern whereas LPS from strains 1536 and 4226 showed a distin ctly different pattern. The antigenic similarities of the LPS of strai ns WF83 and 7317 were confirmed by immunoblots using rabbit or pig ant isera prepared against the 3 strains. No antigenic similarities in the LPS of strains 1536 and 7317 were revealed. Since an antigenic determ inant specific for the 9 isolates could not be demonstrated with the m ethods used, the strains are proposed to be designated K2:O7.