Molecular Diagnostics of Infectious Diseases

With the advances in molecular biology, molecular testing has been incorporated into pathogen testing for infectious diseases. There are two main objectives for the molecular diagnosis of infectious diseases- first, to detect pathogen genes by using highly sensitive nucleic acid amplification tests, such as polymerase chain reaction and isothermal amplification, and second, to characterize the properties of the pathogen using next-generation sequencing. Polymerase chain reaction plays a key role in molecular testing. The extensive development of polymerase chain reaction methods is underway, focusing on the acceleration of reaction time (microfluidic polymerase chain reaction), quantification (real-time polymerase chain reaction, digital polymerase chain reaction), full automation, and point-of-care testing. Isothermal amplification is a method for amplifying nucleic acids at a constant temperature. Loop-mediated isothermal amplification, recombinase polymerase amplification, and nucleic acid sequence-based amplification have been developed for isothermal amplification. Isothermal amplification does not require a thermal cycler or simplified temperature control; therefore, it is suitable for point of care testing. CRISPR-based diagnostics are a new method for detecting amplified nucleic acids. CRISPR-Cas reaction proceeds at a constant temperature, it is often combined with isothermal amplification. Next-generation sequencing has a high sequence throughput to rapidly obtain large amounts of genomic information and can be used to detect novel pathogens and diagnose complex infectious diseases. It can also be used to track the sources and transmission routes of outbreaks and monitor pathogen evolution. Furthermore, next generation sequencing has enabled the analysis of microbiomes that can serve as biomarkers for diseases or disease susceptibility. In the future, the molecular diagnosis of infectious diseases will advance by overcoming these shortcomings and integrating various technologies as hybrid platforms. This review describes the developments in molecular diagnostics for the treatment of infectious diseases.