Molecular diagnostic techniques

Molecular diagnostic techniques will continue to transform clinical microbiology. They provide more rapid and sensitive testing that impacts directly on clinical management of infected patients. Molecular diagnostic tests arose from the need to detect micro-organisms that are slow or difficult to grow, or that are present in only small numbers. Nucleic acid amplification techniques (e.g. polymerase chain reaction, PCR) can detect DNA or RNA specific to certain micro-organisms and do not rely on either the recovery of the pathogen or an immune response in the infected patient. Alternative nucleic acid amplification methods have emerged recently because of increasing commercial interest in infectious disease diagnostics and the comprehensive patient protection of PCR technology. Such techniques are gaining widespread acceptance, and have displaced more conventional gold-standard testing in some areas of infectious disease (e.g. viral load testing in HIV-1 infected patients, diagnosis of Chlamydia trachomatis infection). Genetic characterization techniques are increasingly used to determine the relatedness of micro-organisms in the clinical setting. These methods are useful in establishing routes or sources of infection in outbreaks of disease, and are powerful epidemiological tools in large-scale clinical investigations. Recently, there has been a move towards pathogen characterization techniques based on direct nucleotide sequencing (e.g. single nucleotide polymorphism analysis, multi-locus sequence typing). These techniques offer unambiguous, portable data that can be exchanged via the Internet, strengthening collaborative efforts in the field of infectious disease research.