Use of an insertion sequence for laboratory diagnosis and epidemiologic studies of tuberculosis.

A dramatic improvement in the rapidity and accuracy of laboratory testing for tuberculosis is anticipated in the near future from the application of molecular biology techniques. The polymerase chain reaction and other nucleic acid amplification methodologies have the potential to detect, amplify, and identify very small quantities of Mycobacterium tuberculosis DNA directly in a clinical specimen, even on the same day it is collected. Within the past 3 years, a number of polymerase chain reaction-based assays for tuberculosis have emerged. The development and evaluations of the polymerase chain reaction assay based on the insertion sequence IS6110 are described. For practical application in the clinical setting, amplification assays require a simple, reliable sample preparation method; an internal positive control to monitor for inhibitors; a method for eliminating contamination with amplicon (a polymerase chain reaction product) to prevent false-positive results; and a simple, sensitive detection method. The DNA fingerprinting method that uses IS6110 probes provides a means of differentiating individual strains of M tuberculosis and is a powerful tool for epidemiologic studies. The method and its applications are described.