Cloned single copy DNA sequences of Mycobacterium tuberculosis as DNA probes

A recombinant genomic clone was isolated from a lambda gt 11 library of M. tuberculosis on the basis of lack of hybridization with M. avium and M. kansasi. The specificity and sensitivity of M. tb DNA probes, 2.5 and 2.3 kb in size, were assessed by Southern blot and dot blot hybridization. These did not cross hybridize to DNA of mycobacteria other than members of M. tb complex, nor with DNA of non mycobacterial origin. Sensitivity was determined to be 200 pg which is equivalent to 10(4) bacilli. Genomic Southern hybridization indicated single copy nature of the probes.