If we vaccinate the healthy animals with Brucella live vaccine RB51, then what is the possibility that PCR result will be positive or negative?
The degree and duration of bacteremia and tissue colonization with RB51 is likely shorter with RB51 than with field strains of B. abortus. Thus, detection via PCR would likely depend on the length of time between vaccination and sample collection. If the sample does contain DNA of RB51, the likelihood of it testing PCR positive is dependent on the PCR assay used. A Brucella genus specific assay will detect RB51. There are several multiplex PCR assays that can differentiate infected from vaccinated animals. See the following paper:
Clin Chem. 2006 Apr;52(4):779-81.
Multiplex PCR assay for the identification and differentiation of all Brucella species and the vaccine strains Brucella abortus S19 and RB51 and Brucella melitensis Rev1.
García-Yoldi D, Marín CM, de Miguel MJ, Muñoz PM, Vizmanos JL, López-Goñi I.
The abbreviated AMOS assay is based on the insertion of the genetic element IS711 at a unique chromosomal locus in B. abortus bv. 1, 2, and 4 and the double insertion of IS711 at a specific locus in B. abortus RB51. One PCR primer is anchored within the IS711 sequence, while the differentiating primers are localized in the unique chromosomal DNAs adjacent to the insertion. The primers were selected to amplify up to three products of different sizes. The primers amplify a 498-bp product present in B. abortus bv. 1, 2, and 4 plus two vaccine strains, and they also amplify a 364-bp product from B. abortus RB51. Identification of S19 is based on a PCR primer pair which amplifies a short sequence (178 bp) of the eri gene (essential for erythritol catabolism), present in all Brucella strains except B. abortus S19. Thus, the identification of S19 is based on the absence of amplification of this target. so through The abbreviated AMOS PCR assay you can geneticaly differentiate between field and vaccine strains of B. abortus
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