Evaluation of the ability of two multiplex PCR assays(Bruce-ladder and Suis-ladder) to distinguish six Brucella species and Brucella suis at the biovar level

Objective To evaluate the ability of two types of multiplex PCR assays(Bruce-ladder and Suis-ladder) to distinguish six Brucella species and five biovars of Brucella suis.Methods A Bruce-ladder multiplex PCR assay was performed using 8 pairs of primers to distinguish six Brucella species.A Suis-ladder multiplex PCR assay was performed using 4 pairs of primers to distinguish five biovars of B.suis.The tested strains,which consisted of 27 reference strains of six Brucella species and 239 Brucella isolates,were examined using PCR assays and methods of biological identification.Results The Bruce-ladder multiplex PCR assay differentiated six Brucella species,including Brucella abortus,Brucella melitensis,Brucella suis,Brucella canis,Brucella ovis,and Brucella neotomae,in a single step.The Suis-ladder multiplex PCR assay differentiated five biovars of B.suis in a single step.The electrophoresis patterns of the vaccine strain S2 and biovar 1 of B.suis were identical.The total rate of concordance between methods of biological identification and multiplex PCR assays was 100%.Conclusion The Bruce-ladder and Suis-ladder multiplex PCR assays are rapid and specific methods of respectively identifying Brucella species and B.suis at the biovar level.