A highly sensitive and specific diagnostic test forBrucellabased on polymerase chain reaction is under development in our laboratory. A commercially available PCR kit was used to create primers that allowed the amplification of a 635 bp fragment of a 43 kDa outer membrane protein gene fromBrucella abortusstrain 19. We successfully amplified the cloned gene present in the pMS64 plasmid and genomicBrucellaS19 DNA. The amplified DNA was easily detected by agarose gel electrophoresis. Using both the pMS64 plasmid andBr. abortusS19 purified DNA as template each component of the PCR reaction was adjusted for the optimum amplification of the DNA sequence. Optimum specific amplification resulted when the primer annealing temperature was 60d̀C. The gene fragment was amplifiable in 25 differentBrucellaspecies and strains. To test the specificity of the reaction, DNA extracted from 17 micro‐organisms possibly associated with cattle were tested. No amplification was observed. The sensitivity of the reaction was determined with different concentrations of genomicBrucellastrain 19 DNA. As little as 0.1 pg DNA (less than 100 brucella cells) could be detected. The specificity and sensitivity of PCR combined with its simplicity and speed suggests the potential of this technique for routine diagnosis of brucellos
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