Genetic Structure ofCandida glabrataPopulations in AIDS and Non-AIDS Patients

Abstract

Analysis of the population genetics structure of natural populations elucidates the functioning and evolutionary capabilities of natural populations. It is particularly appropriate for organisms that cannot be directly observed (37). Indeed, the genotypic structure can provide useful clues for estimating the reproductive mode, gene flow, geographical structure, and approximate sizes of reproductive units (10).Infectious diseases involve organisms whose population biology is difficult to assess. This is why molecular markers are useful tools in increasing our understanding of their epidemiology (40).Candidoses are cosmopolitan infections due to yeast-like fungi. These yeasts are responsible for severe mucocutaneous or systemic infections, particularly in premature infants, pregnant women (in that case the infection is mildly self-limiting), after invasive intervention, in AIDS and immunodeficient patients (e.g., cancer, graft, and transplantation patients), and during chemotherapy (corticoids or antimitotics) and radiotherapy (26). Oropharyngeal candidosis is the earliest and the most common fungal infection found in AIDS patients (5, 6, 16). Moreover, susceptibility to other mycoses increases with the development of AIDS (17). Primary infections are essentially due to Candida albicans. After antifungal treatments, relapses are common and are often due to Candida glabrata (also known as Torulopsis glabrata) (2,7,18). Furthermore, the use of antifungal azoles seems to enhance the development of such mycoses (8,15).C. glabrata is a commensal yeast commonly isolated from the human digestive tract. This yeast is considered to be haploid and without a sexual cycle (45). Until know, very little attention has been devoted to the genetics of this opportunistic pathogen compared to the related C. albicans (1,3,28,48). Thus, basic information on the biology and epidemiology of C. glabrata is needed.We report here the enzyme polymorphism observed for 33 putative gene loci in 63 C. glabrata strains in 11 reference strains and in 52 strains isolated from hospitalized patients (22 in Paris and 30 in Montpellier). Furthermore, the patterns of 24 RAPD [random(ly) amplified polymorphic DNA] primers from 20 of these strains are compared to the multilocus enzyme electrophoresis (MLEE) results. This allows inferences to be made regarding the genetic structure and reproductive modality displayed by C. glabrata populations with respect to geography, infected organs, and the human immunodeficiency virus (HIV) status of the patient. MATERIALS AND METHODSOrigin of the different strains. We used 11 reference strains. Strain 774 comes from the Centraalbureau voor Schimmelcultures (Delft, The Netherlands), along with the reference CBS 138 T ; strains 918, 949, 957, 960, 962, 965, 970, and 971 were provided by the Institut Pasteur (Paris, France) with reference numbers IP 3, 811,13,20,14,12,32, and 9, respectively, and strains 1109 and 1110 came from SANOFI (Montpellier, France) with reference numbers SANOFI 2223 and 2231.

Assessment of Candida glabrata Strain Relatedness by Pulsed-Field Gel Electrophoresis and Multilocus Sequence Typing

“…When these isolates were analyzed for their drug susceptibilities, no correlation between reduced susceptibility and the MLST or the PFGE genotype was found, which is in concordance with the findings presented in previous reports (15,16). No correlations were found between genotypes and clinical information, such as anatomic sources and hospital origin.…”

Multilocus Sequence Typing of Candidaglabrata Reveals Geographically EnrichedClades

“…We found that the most representative C. glabrata groups in Europe, the United States, and Japan were groups I and II, groups II and III, and groups III and IV, respectively. The population structure of C. glabrata is believed to be predominantly clonal (5). The results we have obtained on geographical specificity tend to support the conclusion that mixing between clades is depressed.…”

“…These have included the description of phenotypic switching (19,20), the demonstration of pseudohypha and tube formation (4,19), and the identification and characterization of a mating system that is similar to that of Saccharomyces cerevisiae (41,44). Studies of the population structure of the organism have also begun to emerge (5). To facilitate the latter, we have developed and begun to characterize a fingerprinting method based upon multilocus sequencing.…”

“…A number of different genetic fingerprinting methods have previously been applied to C. glabrata (40), including random amplification of polymorphic DNA (RAPD) (22,24), pulsedfield gel electrophoresis (PFGE) (17,42), multilocus enzyme electrophoresis (MLEE) (5), and fingerprinting with complex DNA probes (24). To date, there has only been one example of direct sequence comparison for typing C. glabrata (38).…”

Microsatellite Marker Analysis as a Typing System for Candida glabrata

“…However, few tools are available to study the source of contamination, cross-contamination of patients at risk, and the biology of this yeast, which has, unlike C. albicans, a haploid genome (10). Studies of population structure have begun to emerge using enzymatic and randomly amplified polymorphic DNA typing (6) or sequencing of the cytochrome c oxidase subunit 2 gene (24). Recently, a technique based on the sequencing of six variable-locus genes, or multilocus sequence typing (MLST), has been proposed as a powerful typing method (7).…”