Molecular techniques in clinical microbiology:

Principle conventional methods are include; cultivation and physiological characteristics of microorganisms , which are focusing on phenotypes. The phenotypic methods have some limitations and disadvantages;
1. Inability to grow certain fastidious pathogens.
2. Inability to maintain viability of certain pathogens in specimen during transport to laboratory.
3. Extensive delay in cultivation and identification of slowly growing pathogens.
4. Lack of reliable method to identify certain pathogens.
Molecular methods are focusing on microbial genes(genotypes), by which can be solve the above problems. In addition to that, the molecular methods are more rapid detection and identification of organism that grow slowly.

NUCLEIC ACID–BASED METHODS
Nucleic acid–based tests are highly specific, quite sensitive, and much faster than culturing the organism. Three methods of N.A-based:
• Nucleic acid amplification tests utilize the polymerase chain reaction (PCR) or other amplifying process to increase the number of bacteria-specific DNA or RNA molecules so the sensitivity of the test is significantly higher than that of unamplified tests.
• Nucleic acid hybridization: probes are designed to detect bacterial DNA or RNA directly (without amplification) using a labeled DNA or RNA probe that will hybridize specifically to the bacterial nucleic acid. These tests are simpler to perform than the amplification tests but are less sensitive.
• Nucleic acid sequence analysis is used to identify bacteria based on the base sequence of the organism’s ribosomal RNA(rRNA).