DNA amplification assay for rapid detection of bovine tubercle bacilli in semen.

Tubercle bacilli shed in the semen can be a potential hazard for unlimited number of cows through artificial insemination. We have evaluated the efficacy of a DNA amplification technique by polymerase chain reaction (PCR) for the detection of tubercle bacilli in fresh and frozen semen using spiked samples. The test was based on insertion sequence IS 1081 and could detect as low as 10-100 bacterial cells per ml of spiked semen. The specificity of the test was 100%. The method was applied to semen samples from known and suspected tuberculous bulls. Each of 20 semen samples (fresh and frozen diluted) from one of the three breeding bulls included in the study was found positive while the remaining 40 samples from the other two bulls failed to generate any detectable signal. PCR products were confirmed with Southern blot hybridization to an alpha 32P labeled-PCR product of the target sequence from the IS 1081 element of the Mycobacterium tuberculosis complex.