Detection and differentiation of fungi in clinical specimens using polymerase chain reaction (PCR) amplification and restriction enzyme analysis

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Abstract
We have developed a method for processing and detecting fungi in clinical specimens using the polymerase chain reaction (PCR) methodology. This PCR amplification of a segment of a ribosomal DNA gene results in a 310 bp product. The gene sequences used as amplimers have been highly conserved throughout the fungal kingdom and positive PCR results have been obtained for all genera and species of fungi tested (n = 42). Neither human nor a variety of pathogenic bacteria (n = 24) gave an amplified product. This PCR method can detect as few as 15 cells of Candida albicans in clinical specimens following a simple processing procedure. The sensitivity of the PCR for detecting other fungi remains to be determined. Analysis of the 310 bp amplified product, following digestion with the restriction enzyme HaeIII, can be used to further characterize the identity of the fungus involved into the following five groups: (i) Candida species and closely related yeasts; (ii) Cryptococci and Trichosporon species; (iii) Aspergilli and clinically related septate molds; (iv) the Zygomycetes; and (v) the dimorphic fungi.