Molecular detection of pathogens (molecular microbiology) is a new, dynamic and progressive arm of the classic, cultivation-based microbiology. It plays an important role in clinical situations when standard microbiology (relying on the successful cultivation of potential pathogens) produces suboptimal results or completely fails.
Classic, cultivation-based microbiology is a diagnostic mainstay that deals with cultivation requirements of individual microorganisms (bacteria, fungi, viruses) and their biochemical properties. The absolute requirement for the identification of a microorganism is its successful cultivation in supportive cultivation media, followed by the identification itself (morphology, biochemistry, MALDI-TOF). If the microorganism is cultivatable, classic microbiology can also detect its antibiotic/antimycotic resistance. Nevertheless, in cases of uncultivatable agents (for example Ehrlichia, Borrelia, Chlamydia), fastidious pathogens (viruses, strictly anaerobic microorganisms), or microbes with compromised fitness (sub-optimally sampled specimens, long or sub-optimal transport conditions), the classic cultivation-based microbiology might completely fail.
Molecular microbiology does not deal with cultivation requirements of individual microorganisms. Molecular microbiology relies on the precise quantitative identification of unique DNA/RNA spectra of the agents in any biological material. Using this approach, microorganisms are not only accurately identified, but the technology also allows for their precise quantitation. The quantitative finding is of high clinical relevance for the assessment of the causality of the agents identified; especially if primarily non-sterile biological material is investigated (mixed-microbial flora specimens). If more than one pathogen is present is the biological sample, the quantitative analysis can address their potential clinical importance.
Molecular microbiology plays an important diagnostic role in clinical situations when classic microbiology, based on the cultivation of microbial agents fails due to its technical limitations (uncultivatable or fastidious agents) or its often-sub-optimal speed (several days/weeks needed to successfully cultivate and identify the causative microorganism).