Serogrouping ofRhodococcus equi

Abstract

The serological relationships among 27 isolates of R. equi selected from a total of 1195 isolates were investigated by cross-agglutination and absorption tests. The presence of capsular material was demonstrated in all the 27 isolates by EM observation. Antisera were prepared by employing formalized antigen of each isolate. In the cross-agglutination test with formalized antigen, 13 rabbit antisera reacted with homologous antigens alone, but the remaining 14 antisera reacted not only with homologous antigens but also with 1-4 heterologous antigens. When these 14 antisera possessing heterologous agglutinins were absorbed with each of the crossreacting antigens, 14 specific antisera were obtained. The crossagglutination test with these 27 antisera proved the 27 strains examined to be serologically distinct from one another. These strains were designated serogroups 1-27. Thus the same number of grouping antisera were prepared. The distribution of each serogroup among the 1195 isolates and 15 reference strains was investigated by the slide agglutination test. All the strains were found to be groupable. Most of them belonged to serogroups 1-4, 7-9, 11, 14 and 15. Of the serogroups designated 4, 16, 2, 12, 21, 1 and 9 were identical with Prescott''s serovars 1, 2, 3, 4, 5, 6 and 7, respectively.