Novel Polymorphic Multilocus Microsatellite Markers to Distinguish Candida tropicalis Isolates

Area of Science:

• Medical Mycology
• Molecular Genetics
• Population Genetics

Background:

• Candida tropicalis is a significant opportunistic fungal pathogen.
• Accurate genotyping is crucial for tracking C. tropicalis infections and understanding its population structure.
• Existing genotyping methods may have limitations in discriminatory power or throughput.

Purpose of the Study:

• To develop and evaluate a novel polymorphic multilocus microsatellite scheme for the genotyping of Candida tropicalis.
• To identify new genetic markers for high-resolution typing of C. tropicalis isolates.
• To assess the discriminatory power and efficiency of the developed microsatellite scheme.

Main Methods:

• Screening of over 4000 tandem repeats in the C. tropicalis genome to identify novel microsatellite loci.
• Selection of six candidate microsatellite loci (ctm1, ctm3, ctm8, ctm18, ctm24, ctm26) based on amplification success, polymorphism, and stability.
• Testing the six-locus scheme and two known loci (CT14, URA3) against 82 isolates from 32 patients.
• Comparison of microsatellite typing results with pulsed-field gel electrophoresis (PFGE).

Main Results:

• The six-locus microsatellite scheme successfully genotyped isolates, with identical genotypes found for isolates from the same patient.
• The scheme identified 11 to 24 genotypes among 32 patients' isolates, with a discriminatory power (DP) ranging from 0.76 to 0.97.
• A combination of three loci (ctm1, ctm3, ctm24) achieved a maximum typing efficiency (DP = 0.99) and identified 29 genotypes.
• The microsatellite scheme showed good correlation with PFGE but was slightly less discriminatory.

Conclusions:

• The developed six-locus microsatellite typing scheme is a valuable and efficient tool for the genotyping of Candida tropicalis.
• This scheme can aid in epidemiological investigations and understanding the microevolution of C. tropicalis.
• The identified novel microsatellite loci offer improved resolution for typing this important fungal pathogen.