Detection and identification of infectious organisms: Application of molecular probe technology

Development in molecular biology and biotechnology has provided clinical laboratories with new tools for the study and diagnosis of human diseases including genetic diseases, chronic disorders, malignant diseases and infectious diseases. The basis of molecular diagnosis is the identification of nucleic sequences that are informative in a disease and the detection of these sequences by specific nucleic acid probes. The most widely applied molecular technique for the detection of pathogenic organisms in clinical specimens is hybridization analysis. In this assay system, nucleic acid of defined specificity is used to ''probe'' for the presence of genomic sequences of target organisms. This technology has been used for the detection of a variety of pathogens including viruses, bacteria and parasites in tissues, blood, stools, urine and a variety of body secretions. The applications of hybridization analysis in the diagnostic laboratory include (i) the rapid detection of pathogens directly in clinical specimens and (ii) the identification of pathogens isolated in culture. The practical use of molecular probes to detect pathogens directly in clinical specimens requires that target sequences be amplified, either by culture or by in vitro amplification, prior to hybridization analysis. The coupling of in vitro amplification and nucleic acid hybridization renders the technique highly sensitive and specific. In the case of organisms that are slow to grow in culture, this strategy provides the added advantage of speed. Therefore, molecular based diagnosis would particularly useful in instances where the pathogenic organism is difficult to culture or grows slowly in culture and where rapid diagnosis is life-saving, as in the case of infections by opportunistic organisms in immunosuppressed patients. (author). 7 refs