Molecular cloning of a highly repeated DNA element from Mycobacterium tuberculosis and its use as an epidemiological tool

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Abstract
In order to develop a technique for distinguishing between isolates of Mycobacterium tuberculosis, we cloned two hypervariable DNA fragments from NdeII-digested genomic DNA. The cloned DNA fragments of 3.8 and 4.7 kb were found to contain the same repetitive element, which was different from previously characterized repetitive elements. It is present in at least 30 copies per genome and is distributed among mycobacterial species other than those of the tuberculosis complex, including M. kansaii, M. gastri, and M. szulgai. When used as a probe on restriction enzyme-digested DNA, it can distinguish between strains from unrelated cases of tuberculosis while demonstrating identical banding patterns for isolates from epidemiologically related cases.