Accurate identification of mold isolates is an essential task of the clinical microbiology laboratory that enables initiation of proper antimicrobial therapy. For many molds, traditional phenotypic identification is difficult, laborious and time-consuming. Identification often takes 4 weeks or more to identify an isolate to the species level. This issue is confounded by phenotypic variation within species, many newly described pathogenic species and the limited battery of phenotypic tests available to distinguish among all established and potential fungal pathogens. It is sometimes essential to identify mold isolates to species level in order to detect unsuspected pathogens, ascribe pathogenicity to species so far considered to be nonpathogenic and to identify new mold species. PCR amplification and sequencing of mold 26S ribosomal RNA (rRNA) and Internal Transcribed Spacer 1 and 2 regions (ITS1 & ITS2) provides rapid, accurate identification of clinically significant molds. These target DNA fragments contain signature sequences useful for mold identification to species level, flanked by conserved regions that are useful for the design of universal PCR primers.
In many specimens fungal elements can be seen by microscopy of tissue sections but are very difficult to grow due to their fastidious nature, or are not viable as a result of antifungal therapy. Some specimens may never reveal the presence of a fungal pathogen because of low abundance and/or lack of viability. The use of PCR to detect this DNA extracted directly from clinical specimens facilitates the identification of these pathogens.
For interesting cases emplyoying this test methodology, please see our Clinical Significance page.
