Rapid identification of rough Brucella isolates by a latex coagglutination assay with the 25-kilodalton outer membrane protein and rough-lipopolysaccharide-specific monoclonal antibodies.

A latex coagglutination assay was developed to identify rough (R) isolates of Brucella. Latex beads were coated, via protein A, with either an anti-Brucella rough-lipopolysaccharide (R-LPS) monoclonal antibody (MAb) or an anti-Brucella 25-kDa outer membrane protein (Omp25) MAb. Slide agglutination tests were done for 68 strains of Brucella spp., including type strains of all biovars as well as field isolates. Latex beads coated with MAb to R-LPS coagglutinated only R strains, whereas latex beads coated with MAb to Omp25 coagglutinated all the R Brucella isolates except Brucella ovis. Coagglutination was easier to read than agglutination with rabbit R-Brucella-specific antiserum. Thus, this assay accurately differentiates B. ovis from other R Brucella isolates. The latex coagglutination assay can substitute, to advantage, for the current anti-Brucella (R) rabbit monospecific serum.