Author(s):
Sabino, Raquel 
; Sampaio, Paula ; Rosado, Laura ; Stevens, David A. ; Clemons, Karl V. ; Pais, Célia
Date: 2010
Persistent ID: http://hdl.handle.net/10400.18/188
Origin: Repositório Científico do Instituto Nacional de Saúde
Subject(s): Infecções Sistémicas e Zoonoses
Description
Among the Candida species causing bloodstream infections, Candida parapsilosis is one of the most frequently
isolated. The objective of the present work was the identification of new microsatellite loci able to distinguish
among C. parapsilosis isolates. DNA sequences with trinucleotide repeats were selected from the C. parapsilosis
genome database. PCR primer sets flanking the microsatellite repeats were designed and tested with 20
independent isolates. On the basis of the amplification efficiency, specificity, and observed polymorphism, four
of the sequences were selected for strain typing. Two hundred thirty-three independent C. parapsilosis sensu
stricto isolates were genotyped by using these markers. The polymorphic loci exhibited from 20 to 42 alleles and
39 to 92 genotypes. In a multiplex analysis, 192 genotypes were obtained and the combined discriminatory
power of the four microsatellites was 0.99. Reproducibility was demonstrated by submission of subcultures of
4 isolates each, in triplicate, interspersed with unique numbers among a group of 30 isolates for blind testing.
Comparison of the genotypes obtained by microsatellite analysis and those obtained by randomly amplified
polymorphic DNA analysis, restriction fragment length polymorphism analysis, and internal transcribed
sequence grouping was performed and showed that the microsatellite method could distinguish individual
isolates; none of the other methods could do that. Related species, C. orthopsilosis and C. metapsilosis, were not
confused with C. parapsilosis sensu stricto. These new microsatellites are a valuable tool for use for the
differentiation of C. parapsilosis sensu stricto strains, vital in epidemiology to answer questions of strain
relatedness and determine pathways of transmission.
