Multilocus Microsatellite Markers for Molecular Typing of Candida glabrata : Application to Analysis of Genetic Relationships between Bloodstream and Digestive System Isolates

Abstract

Candida glabrata has emerged as the second most common etiologic agent, after Candida albicans, of superficial and invasive candidiasis in adults. Strain typing is essential for epidemiological investigation, but easy-to-use and reliable typing methods are still lacking. We report the use of a multilocus microsatellite typing method with a set of eight markers on a panel of 180 strains, including 136 blood isolates from hospitalized patients and 34 digestive tract isolates from nonhospitalized patients. A total of 44 different alleles were observed, generating 87 distinct genotypes. In addition to perfect reproducibility, typing ability, and stability, the method had a discriminatory power calculated at 0.97 when all 8 markers were associated, making it suitable for tracing strains. In addition, it is shown that digestive tract isolates differed from blood culture isolates by exhibiting a higher genotypic diversity associated with different allelic frequencies and preferentially did not group in clonal complexes (CCs). The demonstration of the occurrence of microevolution in digestive strains supports the idea that C. glabrata can be a persistent commensal of the human gut.

Evaluation of Polymorphic Locus Sequence Typing for Candida glabrata Epidemiology

“…Correspondingly, the diversity indexes (excluding epidemiological replicates; see below) were 0.94 and 0.91. These values are comparable to those obtained with other typing methods and strain sets (14,24,32,34,35).…”

“…The most widely applied include (i) multilocus sequence typing (MLST), which analyzes 6 relatively conserved housekeeping loci for single nucleotide polymorphisms (SNPs) (29,30), (ii) pulsed-field gel electrophoresis (PFGE), which compares total DNA banding patterns with or without restriction enzyme digestion (14,23,31), (iii) multilocus variable-number tandem-repeat analysis (MLVA, also known as microsatellite analysis), which examines length variation in 6 to 9 PCR-amplified loci that contain polymorphic tandem repeats (32)(33)(34)(35), and (iv) random amplification of polymorphic DNA (RAPD), which compares banding patterns following PCR with a nonspecific primer (26,36). In general, these methods are comparable in their strain resolution, achieving diversity indexes of ca.…”

Posttreatment Antifungal Resistance among Colonizing Candida Isolates in Candidemia Patients: Results from a Systematic Multicenter Study

“…Indeed, the dominating species was C. glabrata in swabs from both azole-and echinocandin-treated patients, despite the different initial species distributions in blood. This would not explain the prevalence of polyfungal oral swabs, however, and further studies are thus warranted to evaluate these hypotheses (10,30,35,36). One approximation for this study was to interpret the blood isolates as surrogate markers for baseline colonization and to compare this to subsequent oral colonization.…”

“…CLC Main Workbench (CLC-Bio, Qiagen) bioinformatics software with the MLST plug-in was applied to analyze sequence data. One allelic difference were considered microevolution between paired isolates, based on previous findings, and thus isolates were regarded as genetically unrelated if they differed at two or more alleles for all MLST schemes (30,31).…”

Candida albicans Pathogenesis: Fitting within the Host-Microbe Damage Response Framework

“…Therefore, PRRs that recognize fungal moieties may help promote responses to commensals in the GI tract and initiate damage. It is as yet unclear whether GI tract carriage of C. albicans in healthy hosts (up to 50% of individuals) imparts any benefit, but it is often asymptomatic and hence likely does not normally cause damage in the context of normal host responses (119).…”