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False identification of Coccidioides immitis: do molecular methods always get it right?
B Cherie Millar1, Xu Jiru, Michael J Walker
1Northern Ireland Public Health Laboratory, Department of Bacteriology, Belfast City Hospital, Belfast BT9 7AD, Northern Ireland, United Kingdom.
Journal of Clinical Microbiology
|December 10, 2003
Summary
Molecular identification of fungi like Chrysosporium keratinophilum can be mistaken. Using only the 18S rRNA gene for fungal identification may lead to misidentification, necessitating analysis of additional regions like ITS.
Area of Science:
- Medical Mycology
- Molecular Biology
- Fungal Taxonomy
Background:
- Accurate identification of medically important fungi is crucial for effective treatment and public health.
- Molecular techniques, particularly rRNA gene sequencing, are widely used for fungal identification.
- Previous studies have shown potential ambiguities in fungal identification based on limited genetic markers.
Purpose of the Study:
- To investigate potential molecular misidentification of Chrysosporium keratinophilum.
- To evaluate the reliability of using partial 18S ribosomal RNA (rRNA) gene sequences for fungal identification.
- To recommend best practices for molecular identification of medically relevant fungi.
Main Methods:
- Partial sequencing of the 18S rRNA gene and the 5.8S-internal transcribed spacer 2 (ITS2) region.
- Comparative sequence analysis of Chrysosporium keratinophilum.
- Bioinformatic analysis to assess sequence similarity and phylogenetic relationships.
Main Results:
- Sequence analysis revealed that Chrysosporium keratinophilum could be potentially misidentified as Coccidioides immitis based solely on the 18S rRNA gene.
- The ITS2 region provided discriminatory power to differentiate between these fungal species.
- The 18S rRNA gene alone is insufficient for definitive identification of certain medically important fungi.
Conclusions:
- Relying exclusively on 18S rRNA gene sequencing for fungal identification can lead to significant errors.
- Confirmation using additional genetic markers, such as the internal transcribed spacer (ITS) regions, is essential for accurate fungal identification.
- Standardized molecular identification protocols should incorporate multiple genetic loci to ensure species-level resolution.