Real-time PCR as a Diagnostic Tool for Bacterial Diseases

Max Maurin


Expert Rev Mol Diagn. 2012;12(7):731-754. 

In This Article

Five-year View

Obviously, qPCR-based diagnostic tests will continue to expand in the coming years. However, these tests will have to meet three requirements: adaptation of existing diagnostic tests, especially according to the discovery of new variants of target genes of specific pathogens, responsible for false-negative results; expansion of diagnostic applications; and a lower cost. The development of new diagnostic applications may be slowed because of technical limitations, but also because of low profitability for the in vitro diagnostic industry and low cost–effectiveness, especially for rare diseases. On the other hand, new technologies (e.g., microfluidic devices) now allow using smaller volumes of reagents, and thus are less costly.

Ideally, in urgent clinical situations, future qPCR tests should enable early diagnosis and rapid assessment of resistances to first-line antibiotics, in order to significantly influence emergency treatment and patient prognosis. These situations include bacteremia and endocarditis, meningoencephalitis, severe pneumonia (especially nosocomial pneumonia) and neonatal infections, among others.

An important aspect to consider is the possibility to detect in a same clinical sample several pathogens responsible for a given syndrome or clinical situation. These multiparameter assays will greatly improve the management of patients suffering from clinically unspecific infectious diseases. Tests based on multiplex qPCR are well suited for this purpose. However, other technologies will compete with the qPCR method, including high-throughput DNA sequencing, mass spectrometry and PCR arrays.[265]

A stepwise diagnostic approach may also be developed, including detection of bacterial DNA (e.g., 16S rDNA), detection of DNA of the most common pathogens and then detection of rarer etiologies. qPCR tests may also allow evaluation of the severity of disease and patient's prognosis, including by direct detection of bacterial genes encoding specific virulence traits, and by quantification of the bacterial load on admission of the patient.

Finally, qPCR tests may allow in vivo evaluation of the antibiotic therapy, especially by rapid detection of antibiotic resistance genes and by monitoring bacterial load during antibiotic treatment.