[Advances in genetic diagnostics for respiratory tract infections]

The past decade has seen the rapid advancement of molecular biology and its application in the field of infectious diseases. The polymerase chain reaction (PCR) is a technique which brings about the in vitro amplification of DNA, and is clinically useful in the sensitive, specific and rapid diagnosis of various infectious diseases. The fast diagnosis of viral infections using PCR is a prime example, since viral culture may take weeks to grow and since serologic conversion seldom occurs until the convalescent phase of the clinical illness. Similarly, PCR is applicable to the diagnosis of pulmonary infections caused by mycobacteria, Legionella, methicillin-resistant Staphylococcus aureus, anaerobes, Mycoplasma, Chlamydia, Pneumocystis carinii and so on. On the other hand, the drug-resistant phenotype of a microorganism is predictable by the detection of gene alterations related to the drug resistance. For example, the deletion of the catalase-peroxidase gene relating to isoniazid resistance of mycobacteria, and point mutations in the RNA polymerase beta subunit (rpoB) gene relating to rifampicin resistance have been elucidated. As these applied techniques become more widely available and less costly, they should contribute not only to the rapid diagnosis of infectious diseases, but also to the adequate selection of antibiotics and the shortening of hospitalization.