DNA Typing of a Nonviable Culture of Mycobacterium tuberculosis in a Homeless Shelter Outbreak

As part of a larger investigation of a 1997 tuberculosis outbreak at a homeless shelter in upstate New York, it became necessary to provide DNA typing data from a nonviable strain of Mycobacterium tuberculosis. Patient A, initially diagnosed with tuberculosis in 1992, was believed to be the source of infection in this outbreak. We wished to know whether the 1997 M. tuberculosis isolate from patient A represented a reactivation of his 1992 infection or later reinfection by a different strain. The only 1992 samples from patient A were 6-year-old LJ agar slants. Several attempts to recover this strain so that sufficient amounts of DNA could be obtained for IS6110-based restriction fragment length polymorphism analysis (RFLP) (3) were unsuccessful. In response to this, we instead utilized the PCR-based spoligotyping method (2) based on analysis of spacers in the direct-repeat (DR) region ofM. tuberculosis complex organisms.