Species- or subspecies-specific DNA (including complementary DNA (DNA, complementary), conserved genes, whole chromosomes, or whole genomes) used in hybridization studies in order to identify microorganisms, to measure DNA-DNA homologies, to group subspecies, etc. The DNA probe hybridises with a specific mRNA, if present. Conventional techniques used for testing for the hybridization product include dot blot assays, southern blot assays, and DNA:RNA hybrid-specific antibody tests. Conventional labels for the DNA probe include the radioisotope labels 32p and 125i and the chemical label biotin. The use of DNA probes provides a specific, sensitive, rapid, and inexpensive replacement for cell culture techniques for diagnosing infections.

(12 Dec 1998)