Detecting eukaryotic microorganisms

A method for constructing a cDNA probe for use in detecting in a sample, under conditions of predetermined stringency, a target organism belonging to a strain of fungal microorganisms, and not detecting in the sample under such conditions a reference microorganism or any prokaryotic microorganism, includes the steps of determining a nucleotide base sequence in a variable region of small subunit ribosomal RNA from the target organism, the variable region being a region of the small subunit ribosomal RNA that is poorly conserved among eukaryotes and having no corresponding region in prokaryotes; comparing the nucleotide base sequence in the corresponding region of small subunit ribosomal RNA from the reference microorganism, and selecting as a useful probe site a subsequence within the determined sequence; and synthesizing a cDNA complementary to the useful probe site, the cDNA being the probe. Nucleic acid probes are constructed according to the disclosed method. A method for using such a probe for detecting a strain of fungal microorganisms in a sample includes the steps of providing such a probe, deriving RNA from the sample, contacting the probe with the RNA under conditions that allow the probe to hybridize with small subunit rRNA to form hybrid nucleic acid complexes, and detecting the hybrid nucleic acid complexes as an indication of the presence in the sample of the organism. A kit includes such a probe and instructions for its use.