Methodologies in the field of diagnostic microbiology have undergone rapid and phenomenal changes during the past two decades. DNA based molecular methods are rapidly replacing and supplementing the conventional diagnostic methods such as microscopy, culture and biochemical characterization. The drawbacks and limitations of conventional diagnostic methods are circumvented through the application of molecular techniques which enhance speed, sensitivity and specificity of etiologic diagnosis. A spectrum of techniques are being developed to detect and identify the etiologic agents. Nucleic acid probes are used for rapid identification of fastidious and slow growing infectious agents directly in the clinical specimens. Signal amplification methods such as hybrid capture system and branched DNA (bDNA) are designed to overcome the problem of poor sensitivity of the probe hybridization. Nucleic acid amplification (NAA) methods involving the amplification of both probe and target have become increasingly popular. NAA methods basically rely upon PCR derived techniques. Several versions of PCR are now available to cater the needs of clinicians. Versatility, rapidity, reliability and reproducibility are the attributes of these techniques. Real-time PCR offers several advantages over other PCR methods and has become a powerful technique in recent times. Molecular methods can also be employed to quantify the nucleic acid targets for clinical prognosis, treatment, management and detection of drug resistance. Similarly, the information such as mutation detection, DNA sequencing, genomic finger-printing and ribotyping, necessary for epidemiological studies, can be generated through molecular methods.
Infectious diseases, molecular diagnosis, probes, nucleic acid amplification, PCR, epidemiology
