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Molecular Diagnostics of Arthroconidial Yeasts, Frequent Pulmonary Opportunists
Engin Kaplan1, Abdullah M S Al-Hatmi2,3,4,5, Macit Ilkit6
1Division of Mycology, Department of Microbiology, Faculty of Medicine, University of Çukurova, Adana, Turkey.
Abstract:
Magnusiomyces capitatus and Saprochaete clavata are members of the clade of arthroconidial yeasts that represent emerging opportunistic pulmonary pathogens in immunocompromised patients. Given that standard ribosomal DNA (rDNA) identification often provides confusing results, in this study, we analyzed 34 isolates with the goal of finding new genetic markers for classification using multilocus sequencing and amplified fragment length polymorphism (AFLP). The interspecific similarity obtained using rDNA markers (the internal transcribed spacer [ITS] and large subunit regions) was in the range of 96 to 99%, whereas that obtained using protein-coding loci (Rbp2, Act, and Tef1α) was lower at 89.4 to 95.2%. Ultimately, Rbp2 was selected as the best marker for species distinction. On the basis of cloned ITS data, some strains proved to be misidentified in comparison with the identities obtained with phenotypic characters, protein sequences, and AFLP profiles, indicating that different copies of the ribosomal operon were present in a single species. Antifungal susceptibility testing revealed that voriconazole had the lowest MIC against M. capitatus, while amphotericin B had the lowest MIC against S. clavata Both species exhibited in vitro resistance to fluconazole and micafungin.
Insights
New genetic markers, Rbp2, offer improved classification for Magnusiomyces capitatus and Saprochaete clavata, emerging fungal pathogens. This advances accurate identification and antifungal susceptibility understanding in immunocompromised patients.
Area of Science:
- Medical Mycology
- Molecular Biology
- Infectious Diseases
Background:
- Magnusiomyces capitatus and Saprochaete clavata are opportunistic pulmonary pathogens in immunocompromised individuals.
- Standard ribosomal DNA (rDNA) identification methods yield ambiguous results for these species.
- Accurate species identification is crucial for effective antifungal treatment strategies.
Purpose of the Study:
- To identify reliable genetic markers for distinguishing M. capitatus and S. clavata.
- To evaluate the efficacy of multilocus sequencing and AFLP for fungal classification.
- To assess antifungal susceptibility profiles of these emerging pathogens.
Main Methods:
- Analysis of 34 yeast isolates using multilocus sequencing (ITS, Rbp2, Act, Tef1α) and Amplified Fragment Length Polymorphism (AFLP).
- Comparison of genetic marker resolution for species delineation.
- Antifungal susceptibility testing (MIC determination) for voriconazole, amphotericin B, fluconazole, and micafungin.
Main Results:
- Protein-coding loci, particularly Rbp2, provided higher interspecific resolution (89.4–95.2%) compared to rDNA markers (96–99%).
- Rbp2 was identified as the optimal marker for robust species distinction.
- Some strains were misidentified based on ITS data, highlighting potential issues with ribosomal operon heterogeneity.
- Voriconazole was most effective against M. capitatus, and amphotericin B against S. clavata.
- Both species demonstrated in vitro resistance to fluconazole and micafungin.
Conclusions:
- The Rbp2 gene is a superior genetic marker for accurate classification of M. capitatus and S. clavata.
- Multilocus sequencing and AFLP offer improved diagnostic capabilities over traditional rDNA methods.
- Distinct antifungal susceptibility profiles necessitate tailored treatment approaches for infections caused by these yeasts.
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