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Polymorphic internal transcribed spacer region 1 DNA sequences identify medically important yeasts.
Y C Chen1, J D Eisner, M M Kattar
1Department of Laboratory Medicine, University of Washington, Seattle, Washington 98195, USA.
Journal of Clinical Microbiology
|October 30, 2001
Summary
Analyzing internal transcribed spacer 1 (ITS1) and internal transcribed spacer 2 (ITS2) regions accurately identifies clinically significant yeasts. Combining ITS1 and ITS2 polymorphisms reliably identifies 40 yeast species, aiding in diagnosing unusual clinical isolates.
Area of Science:
- Medical Mycology
- Molecular Diagnostics
- Yeast Identification
Background:
- Accurate identification of clinically significant yeasts is crucial for effective treatment.
- Noncoding internal transcribed spacer 2 (ITS2) region polymorphisms are established markers for yeast identification.
- The diagnostic utility of the internal transcribed spacer 1 (ITS1) region remains less explored.
Purpose of the Study:
- To investigate the diagnostic value of internal transcribed spacer 1 (ITS1) noncoding regions for yeast identification.
- To compare the discriminatory power of ITS1 and ITS2 regions, individually and in combination.
- To assess the potential of ITS polymorphisms for identifying novel or unusual yeast pathogens.
Main Methods:
- Amplification of ITS1 and ITS2 regions using polymerase chain reaction (PCR).
- Automated capillary electrophoresis for rapid determination of PCR product length with single-base precision.
- Restriction enzyme analysis for distinguishing yeasts with similar PCR product sizes.
- DNA sequencing of ITS1 regions for detailed allelic analysis and phylogenetic comparisons.
Main Results:
- ITS1 length polymorphisms distinguished 19 species, while ITS2 distinguished 16 species.
- Combining ITS1 and ITS2 analyses identified 30 species (98% of clinical isolates).
- Restriction enzyme analysis and ITS1 sequencing further resolved remaining species, enabling identification of all 40 target species.
- Phylogenetic analysis using ITS sequences showed congruence with 26S rRNA gene trees, with ITS providing higher resolution for closely related species.
Conclusions:
- Analysis of ITS polymorphisms, particularly when combining ITS1 and ITS2 regions, provides a reliable method for identifying 40 clinically significant yeast species.
- ITS1 sequencing offers species-specific alleles valuable for identifying unusual clinical isolates.
- The established database of ITS sequences holds promise for the identification of potentially new pathogenic yeast species.