Korean J Lab Med.  2011 Apr;31(2):107-114. 10.3343/kjlm.2011.31.2.107.

Multilocus Sequence Typing for Candida albicans Isolates from Candidemic Patients: Comparison with Southern Blot Hybridization and Pulsed-field Gel Electrophoresis Analysis

• Myoung Y
• Shin JH
• Lee JS
• Kim SH
• Shin MG
• Suh SP
• Ryang DW

• KMID: 1094350
• DOI: http://doi.org/10.3343/kjlm.2011.31.2.107

Abstract

BACKGROUND
We evaluated the efficacy of multilocus sequence typing (MLST) for assessing the genetic relationship among Candida albicans isolates from patients with candidemia in a hospital setting.
METHODS
A total of 45 C. albicans isolates from 21 patients with candidemia were analyzed. The MLST results were compared with results obtained by Southern blot hybridization (C1 fingerprinting) and pulsed-field gel electrophoresis (PFGE). PFGE analysis included karyotyping and restriction endonuclease analysis of genomic DNAs using BssHII (REAG-B) and SfiI (REAG-S).
RESULTS
The 45 isolates yielded 20 unique diploid sequence types (DSTs) by MLST, as well as 12 karyotypes, 15 REAG-B patterns, 13 REAG-S patterns, and 14 C1 fingerprinting types. Microevolution among intra-individual isolates was detected in 6, 5, 3, 5, and 7 sets of isolates by MLST (1 or 2 allelic differences), REAG-B, REAG-S, C1 fingerprinting, and a combination of all methods, respectively. Among 20 DSTs, 17 were unique, and 3 were found in more than 1 patient. The results of 2 DSTs obtained from 9 patient isolates were in agreement with REAG and C1 fingerprinting patterns. However, the remaining DST, which was shared by 2 patient isolates, showed 2 different PFGE and C1 fingerprinting patterns. In addition, 3 sets of isolates from different patients, which differed in only 1 or 2 alleles by MLST, also exhibited different PFGE or C1 fingerprinting patterns.
CONCLUSIONS
MLST is highly discriminating among C. albicans isolates, but it may have some limitations in typing isolates from different patients, which may necessitate additional analysis using other techniques.

Keyword

Candia albicans; Multilocus sequence typing; Pulsed-field gel electrophoresis; Southern hybridization; Genotyping

MeSH Terms

Alleles
Blotting, Southern
Candida albicans/*classification/genetics/isolation & purification
Candidemia/*microbiology
DNA, Fungal/*analysis
Electrophoresis, Gel, Pulsed-Field
Genotype
Humans
Karyotyping
Multilocus Sequence Typing/*methods

Figure

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  Fig. 1 Representative genotyping patterns of Candida albicans obtained by Southern hybridization with the C1 fragment of the Ca3 probe (C1 fingerprinting), electrophoretic karyotyping (EK), and restriction endonuclease analysis of genomic DNA using SfiI (REAG-S) and BssHII (REAG-B). See Table 2 for detailed information on each isolate from 8 patients (patients 1-8). All sequential isolates had the same karyotype and showed the same or similar REAG and C1 fingerprinting patterns, except for 2 isolates (2-3 and 2-4) from patient 2. Stars indicate the positions of added or deleted bands in the minor patterns for clonal strains from the same patient, suggesting that microevolution had occurred. Three sets of isolates from different patients (isolates 7-1 and 8-1; isolates 8-1 and 2-4; isolates 7-1 and 2-3), which differed in only 1 or 2 alleles according to MLST analysis, revealed different PFGE or C1 fingerprinting patterns.Abbreviations: A, C. albicans ATCC 90028; M, Saccharomyces cerevisiae DNA concatamers as a molecular size marker.

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