Molecular diagnosis of infectious diseases.

The Polymerase Chain Reaction (PCR) is a revolutionary new means of amplifying, i.e., replicating, selected DNA sequences in vitro. This procedure is highly sensitive and rapid, requiring few hours for detection of amplified target DNA whereas it often takes several weeks for the identification of many fastidious organisms by culture. Studies have shown that as few as one microorganism can be detected by PCR. Therefore, it is revolutionizing our ability in the diagnosis of infectious diseases. Currently, this technique is very expensive and complex which will probably restrict its immediate role for diagnosing infections where the causative organism is impossible to culture or untypeable by conventional means. As further progress occurs, however, this powerful technique will be applied as a major new tool to diagnose infections and to the study of individual genome variations.