The role of polymerase chain reaction in the diagnosis of mycobacterial infections

Abstract

The increase in tuberculosis (in some cases resistant to treatment) in certain groups of urban poor and AIDS patients in the developed world and its persistence in the third world makes the control of tuberculosis one of the major health care challenges of the 1990s. Until recently diagnostic techniques had changed little in the last 100 years. Now, however, a number of improved and novel techniques are proving useful. Because of the slow growth of mycobacteria, the polymerase chain reaction (PCR) was identified by many workers as being of use in the diagnosis of tuberculosis. Upwards of 20 different protocols have been successfully applied to the rapid identification of Mycobacterium tuberculosis in low numbers in clinical material. Other mycobacteria (M. avium, M. leprae and M. paratuberculosis) have been detected and a PCR-based technique has been used by one group to identify all the species and subspecies of mycobacteria encountered in the diagnostic laboratory. The use of PCR to prepare DNA probes to insertion sequences (e.g. IS6110) has facilitated the development of molecular typing methods for M. tuberculosis. There is a need to evaluate protocols to determine the best method for a further simplification of methods. The likely development of commercial test systems should result in the widespread and routine use of PCR in time. However, it must be remembered that the technique detects both live and dead bacteria and the precise clinical relevance of PCR results will need to be determined.