Cited by 348Antifungal resistance and susceptibilityFungal and yeast genetics researchYeasts and Rust Fungi Studies

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The evolution of drug resistance in clinical isolates of Candida albicans.

Open access

Abstract

Candida albicans is both a member of the healthy human microbiome and a major pathogen in immunocompromised individuals. Infections are typically treated with azole inhibitors of ergosterol biosynthesis often leading to drug resistance. Studies in clinical isolates have implicated multiple mechanisms in resistance, but have focused on large-scale aberrations or candidate genes, and do not comprehensively chart the genetic basis of adaptation. Here, we leveraged next-generation sequencing to analyze 43 isolates from 11 oral candidiasis patients. We detected newly selected mutations, including single-nucleotide polymorphisms (SNPs), copy-number variations and loss-of-heterozygosity (LOH) events. LOH events were commonly associated with acquired resistance, and SNPs in 240 genes may be related to host adaptation. Conversely, most aneuploidies were transient and did not correlate with drug resistance. Our analysis also shows that isolates also varied in adherence, filamentation, and virulence. Our work reveals new molecular mechanisms underlying the evolution of drug resistance and host adaptation.

Overview

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TL;DR

Genome sequencing of 43 serial Candida albicans isolates from 11 oral candidiasis patients shows that loss-of-heterozygosity events, not aneuploidies, are commonly associated with acquired azole resistance. The study also identifies 240 recurrently mutated genes and evolved changes in adhesion, filamentation, and virulence.

Key findings

  • LOH events were detected in all series, were often persistent and recurrent, and coincided with increased fluconazole MIC; highly recurrent LOH occurred on chromosome 3 right arm (Patients 1, 9, 14, 16, 42, 59; p < 5 × 10−4) and chromosome 5 left arm (Patients 1, 14, 15, 43; p < 0.01), regions containing CDR1/CDR2/MRR1 and ERG11/TAC1.
  • Aneuploidies appeared in at least one isolate from 80% (8/10) of clonal patient series, most often chromosome 5 (6 of 8 patients with an aneuploid isolate), but were mostly transient and did not consistently correlate with MIC changes.
  • Persistent nonsynonymous SNPs outside LOH tracts occurred in 1470 genes; applying recurrence across three or more patient series identified 240 polymorphic genes, enriched for fungal-type cell wall (18 genes, p < 0.0012) and cell surface genes (24 genes, p < 0.00012). Polymorphisms in 166 of the 240 genes appeared with an increase in MIC.
  • Isolates varied in adherence, filamentation, and virulence; increased in vitro fitness generally correlated with virulence traits, but drug resistance often initially reduced fitness in the absence of drug while increasing fitness in its presence.

Methods

  • Illumina paired-end sequencing of 43 colony-purified serial clinical isolates from 11 HIV-infected patients with oropharyngeal candidiasis, plus reference strain SC5314; coverage was 53–283X (103X average). SNP calls were validated by Sequenom iPLEX: 1853/1973 calls concordant (93.9%).
  • Genetic analyses included GATK SNP calling, sliding-window LOH detection, copy-number/ploidy analysis with flow cytometry, maximum-parsimony phylogenetics in PAUP*, persistence/recurrence filtering, and NMF clustering of co-occurring mutations.
  • Phenotypic assays included fluconazole E-test MICs, in vitro competition fitness with and without fluconazole, C. elegans survival, filamentation on Spider agar, and adhesion; 23 recurrently mutated loci with available homozygous deletion mutants were profiled for MIC and fitness.

Limitations

  • Stated: because each clinical sample was purified from a single colony, the study cannot assess population structure at any single time point; formally distinguishing de novo mutation followed by selection from selection on pre-existing variation is not possible with the samples and data at hand; ordering of events cannot be definitively inferred from singly sampled isolates; substantial additional sampling per time point is required to fully interpret fitness patterns.
  • Stated: some endpoint-only changes were treated as persistent because several time courses had only two or three isolates.
  • Evident: the clonal analysis rests on 10 patient series and 43 isolates, with some series containing only two isolates; deletion-mutant testing covered only 23 loci and used loss-of-function mutants, whereas known fluconazole resistance mechanisms are often gain-of-function.

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Crossref · 10.7554/elife.00662

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Figures

Figure 1. Overview of study design. (A) Background, persistent, transient, recurrent, and driver mutations in patient time courses. Shown is a schematic illustration of the genomes of isolates (gray bars) from two patient time courses (Patient A and B, left and right panels, respectively), ordered from the first isolate (progenitor, top) to the last (evolved, bottom). Background mutations (purple) exist in the all isolates; persistent mutations (yellow) are not in the progenitor, but found in all subsequent isolates after their first occurrence; transient mutations (pink) are not in the progenitor and only in some later isolates; recurrently polymorphic genes contain persistent mutations that occur in the same gene in more than one patient (black box). LOH events were also evaluated for persistence (light teal bar). Driver mutations, where a new persistent homozygous allele appears (e.g., G/T > A/A), are annotated in association with persistent LOH events (dark teal) and independent of these events (not shown). Each of these can be associated with a change in phenotype, such as drug resistance (boxes, right). (B) Sampling in the context of de novo mutation and selection bottlenecks. Each strain is a single clone (circle) isolated from an evolving population (represented by a phylogenetic tree). The population evolves and undergoes selective sweeps (dashed lines), with phenotypic changes occurring during the course of infection and treatment (i.e., drug resistance, black: high, white: low; gray scale at bottom). Persistent mutations (yellow lightning bolt) have likely swept through the population, whereas transient mutations (pink lightning bolt) have not. (C) Sampling in the context of selection on existing variation. Selection acts to vary the frequency of different pre-existing genotypes in the population. Persistent mutations (yellow lightning bolt) have risen in the population to a frequency that they are repeatedly sampled (large circles) whereas transient mutations (pink lightning bolt) have not (small circle). DOI: http://dx.doi.org/10.7554/eLife.00662.004
Figure 1. Overview of study design. (A) Background, persistent, transient, recurrent, and driver mutations in patient time courses. Shown is a schematic illustration of the genomes of isolates (gray bars) from two patient time courses (Patient A and B, left and right panels, respectively), ordered from the first isolate (progenitor, top) to the last (evolved, bottom). Background mutations (purple) exist in the all isolates; persistent mutations (yellow) are not in the progenitor, but found in all subsequent isolates after their first occurrence; transient mutations (pink) are not in the progenitor and only in some later isolates; recurrently polymorphic genes contain persistent mutations that occur in the same gene in more than one patient (black box). LOH events were also evaluated for persistence (light teal bar). Driver mutations, where a new persistent homozygous allele appears (e.g., G/T > A/A), are annotated in association with persistent LOH events (dark teal) and independent of these events (not shown). Each of these can be associated with a change in phenotype, such as drug resistance (boxes, right). (B) Sampling in the context of de novo mutation and selection bottlenecks. Each strain is a single clone (circle) isolated from an evolving population (represented by a phylogenetic tree). The population evolves and undergoes selective sweeps (dashed lines), with phenotypic changes occurring during the course of infection and treatment (i.e., drug resistance, black: high, white: low; gray scale at bottom). Persistent mutations (yellow lightning bolt) have likely swept through the population, whereas transient mutations (pink lightning bolt) have not. (C) Sampling in the context of selection on existing variation. Selection acts to vary the frequency of different pre-existing genotypes in the population. Persistent mutations (yellow lightning bolt) have risen in the population to a frequency that they are repeatedly sampled (large circles) whereas transient mutations (pink lightning bolt) have not (small circle). DOI: http://dx.doi.org/10.7554/eLife.00662.004CC BY · PubMed Central
Figure 1—figure supplement 1. Analysis of discordant sites. (A) Degree of concordance (Y axis) with Sequenom iPlex genotyping for 1973 SNP X strain combinations overall (leftmost red bar; 93.9%) and in each tested strain (X axis). (B) Shown are the classes of discordant sites by genotype as defined by Illumina (orange) or Sequenome (teal) (X axis) and the prevalence (Y axis) of that genotype call in Sequenom (blue) and Illumina (orange) based discordant calls. The most common discrepancies arose when Sequenom typing classified a site as homozygous, but Illumina sequencing identified it as heterozygous. (C–G) Comparison on distributions of quality features between concordant (blue bars) and discordant (green bars) sites: (C) depth of coverage, (D) RMS Mapping Quality (MQ) score, (E) PHRED scaled quality score for each base call, shown as log-normalized ‘QUAL’ scores, (F) quality by depth (QD) score for each variant site, and (G) the allele balance ratio (AB Score) for each variant site. DOI: http://dx.doi.org/10.7554/eLife.00662.005
Figure 1—figure supplement 1. Analysis of discordant sites. (A) Degree of concordance (Y axis) with Sequenom iPlex genotyping for 1973 SNP X strain combinations overall (leftmost red bar; 93.9%) and in each tested strain (X axis). (B) Shown are the classes of discordant sites by genotype as defined by Illumina (orange) or Sequenome (teal) (X axis) and the prevalence (Y axis) of that genotype call in Sequenom (blue) and Illumina (orange) based discordant calls. The most common discrepancies arose when Sequenom typing classified a site as homozygous, but Illumina sequencing identified it as heterozygous. (C–G) Comparison on distributions of quality features between concordant (blue bars) and discordant (green bars) sites: (C) depth of coverage, (D) RMS Mapping Quality (MQ) score, (E) PHRED scaled quality score for each base call, shown as log-normalized ‘QUAL’ scores, (F) quality by depth (QD) score for each variant site, and (G) the allele balance ratio (AB Score) for each variant site. DOI: http://dx.doi.org/10.7554/eLife.00662.005CC BY · PubMed Central
Figure 2. Most isolates from the same patient are clonal. (A) Two possible models of infection may underlie serial isolates. In the ‘clonal model’ (top) each subsequent sample (circle) is related to the other isolates. In the non-clonal model (bottom) isolates in a series are un-related. (B) The phylogenetic relationship of the isolates (black) from 11 patients (blue) was inferred based on 201,793 informative SNP positions using maximum parsimony in PAUP*. Isolates from the same patient separated by a branch distance greater than 20,000 were considered non-clonal (3281, 2823, 3184, 1691, red). Most nodes were supported by 100% of 1000 bootstrap replicates (indicated by *), expect as indicated (in gray). Clade identifiers were included as appropriate. DOI: http://dx.doi.org/10.7554/eLife.00662.006
Figure 2. Most isolates from the same patient are clonal. (A) Two possible models of infection may underlie serial isolates. In the ‘clonal model’ (top) each subsequent sample (circle) is related to the other isolates. In the non-clonal model (bottom) isolates in a series are un-related. (B) The phylogenetic relationship of the isolates (black) from 11 patients (blue) was inferred based on 201,793 informative SNP positions using maximum parsimony in PAUP*. Isolates from the same patient separated by a branch distance greater than 20,000 were considered non-clonal (3281, 2823, 3184, 1691, red). Most nodes were supported by 100% of 1000 bootstrap replicates (indicated by *), expect as indicated (in gray). Clade identifiers were included as appropriate. DOI: http://dx.doi.org/10.7554/eLife.00662.006CC BY · PubMed Central
Figure 2—figure supplement 1. SNP heterozygosity profiles for each strain. The heterozygosity profiles shows, in chromosomal order (top), each variant locus that exists in at least one strain in the series (white is a heterozygous SNP, blue is homozygous for the SC5314 allele, red is a homozygous SNP relative to SC5314). (A) Patient 1; (B) Patient 7; (C) Patient 9; (D) Patient 14; (E) Patient 15; (F) Patient 16; (G) Patient 30; (H) Patient 42; (I) Patient 43; (J) Patient 59. Only Patient 9 (C), Patient 16 (F), Patient 42 (H), and Patient 64 (not shown**) contain un-related isolates. ** Patient 64 contained an isolate (4380) whose genome aligned poorly to the C. albicans reference, but aligned well to C. dubliniensis. DOI: http://dx.doi.org/10.7554/eLife.00662.007
Figure 2—figure supplement 1. SNP heterozygosity profiles for each strain. The heterozygosity profiles shows, in chromosomal order (top), each variant locus that exists in at least one strain in the series (white is a heterozygous SNP, blue is homozygous for the SC5314 allele, red is a homozygous SNP relative to SC5314). (A) Patient 1; (B) Patient 7; (C) Patient 9; (D) Patient 14; (E) Patient 15; (F) Patient 16; (G) Patient 30; (H) Patient 42; (I) Patient 43; (J) Patient 59. Only Patient 9 (C), Patient 16 (F), Patient 42 (H), and Patient 64 (not shown**) contain un-related isolates. ** Patient 64 contained an isolate (4380) whose genome aligned poorly to the C. albicans reference, but aligned well to C. dubliniensis. DOI: http://dx.doi.org/10.7554/eLife.00662.007CC BY · PubMed Central
Figure 3. LOH events were often persistent while aneuploidies were often transient. For each time series shown are the genomes of all isolates (rows) from a patient, ordered from the first isolate (progenitor, top) to the last (evolved, bottom). Boxes on right indicate the MIC of the respective strain (black: high, white: low; gray scale at bottom). Persistent LOHs: blue, transient LOHs: pink; trisomies (all transient): green. The sequence coverage along each chromosome is indicated by black tickmarks. (A) Patient 1 has four LOH events, each coinciding with an increase in MIC (gray scale boxes, right). One LOH is transient (isolate 2, chromosome R, pink) and three are persistent (isolate 3, chromosome 3; isolate 13, chromosome 5; and isolate 16, chromosome 5, blue). The ploidy changes (isolates 6, 8, 13) are all transient. (B) Patient 7 has one LOH event (isolate 2307, chromosome 3, blue) which coincides with an increase in MIC. DOI: http://dx.doi.org/10.7554/eLife.00662.010
Figure 3. LOH events were often persistent while aneuploidies were often transient. For each time series shown are the genomes of all isolates (rows) from a patient, ordered from the first isolate (progenitor, top) to the last (evolved, bottom). Boxes on right indicate the MIC of the respective strain (black: high, white: low; gray scale at bottom). Persistent LOHs: blue, transient LOHs: pink; trisomies (all transient): green. The sequence coverage along each chromosome is indicated by black tickmarks. (A) Patient 1 has four LOH events, each coinciding with an increase in MIC (gray scale boxes, right). One LOH is transient (isolate 2, chromosome R, pink) and three are persistent (isolate 3, chromosome 3; isolate 13, chromosome 5; and isolate 16, chromosome 5, blue). The ploidy changes (isolates 6, 8, 13) are all transient. (B) Patient 7 has one LOH event (isolate 2307, chromosome 3, blue) which coincides with an increase in MIC. DOI: http://dx.doi.org/10.7554/eLife.00662.010CC BY · PubMed Central
Figure 4. Persistent and transient LOH and aneuploidies. For each time series shown are the genomes of all isolates (rows), ordered from the first isolate (progenitor, top) to the last (evolved, bottom). Boxes on right indicate the MIC of the respective strain (black: high, white: low, gray scale at bottom). Persistent LOHs: light blue, transient LOHs: pink; trisomies (all transient): green. The coverage along each chromosome is indicated by black tickmarks. (A) Patient 9; (B) Patient 14; (C) Patient 15; (D) Patient 16; (E) Patient 30; (F) Patient 42; (G) Patient 43; (H) Patient 59. Several LOHs are recurrent (right arm of chromosome 3, left arm of chromosome 5, and chromosome 1). Please note: data in Figure 3—source data 1 also applies to this figure. DOI: http://dx.doi.org/10.7554/eLife.00662.012
Figure 4. Persistent and transient LOH and aneuploidies. For each time series shown are the genomes of all isolates (rows), ordered from the first isolate (progenitor, top) to the last (evolved, bottom). Boxes on right indicate the MIC of the respective strain (black: high, white: low, gray scale at bottom). Persistent LOHs: light blue, transient LOHs: pink; trisomies (all transient): green. The coverage along each chromosome is indicated by black tickmarks. (A) Patient 9; (B) Patient 14; (C) Patient 15; (D) Patient 16; (E) Patient 30; (F) Patient 42; (G) Patient 43; (H) Patient 59. Several LOHs are recurrent (right arm of chromosome 3, left arm of chromosome 5, and chromosome 1). Please note: data in Figure 3—source data 1 also applies to this figure. DOI: http://dx.doi.org/10.7554/eLife.00662.012CC BY · PubMed Central
Figure 5. Co-occurrence of nonsynonymous substitutions across isolates reveals functional clusters. (A) For each of the recurrently mutated 240 genes (genes in which nonsynonymous persistent SNPs appear in more than three patients and are not within an LOH region), we constructed a patient-by-gene binary vector. We clustered the resulting patient-by-gene matrix using NMF clustering to reveal five coherent clusters (correlation matrix of the clusters left; red: positive correlation; blue: negative correlation; white: no correlation). (B) Co-occurrence clusters. For the genes in each cluster (rows), shown are their mutated occurrences in each patient (columns); green: gene is persistently mutated in patient, white: no persistent mutation, yellow circle: driver mutation. Functional enrichment of clusters was revealed using gene ontology, and genes matching the enriched cluster function are bolded. We have overlaid recurrent driver mutations (e.g., G/T > A/A) (n = 17) occurring outside of LOH regions (yellow circle, green box) and inside LOH regions (yellow circle, white box). DOI: http://dx.doi.org/10.7554/eLife.00662.014
Figure 5. Co-occurrence of nonsynonymous substitutions across isolates reveals functional clusters. (A) For each of the recurrently mutated 240 genes (genes in which nonsynonymous persistent SNPs appear in more than three patients and are not within an LOH region), we constructed a patient-by-gene binary vector. We clustered the resulting patient-by-gene matrix using NMF clustering to reveal five coherent clusters (correlation matrix of the clusters left; red: positive correlation; blue: negative correlation; white: no correlation). (B) Co-occurrence clusters. For the genes in each cluster (rows), shown are their mutated occurrences in each patient (columns); green: gene is persistently mutated in patient, white: no persistent mutation, yellow circle: driver mutation. Functional enrichment of clusters was revealed using gene ontology, and genes matching the enriched cluster function are bolded. We have overlaid recurrent driver mutations (e.g., G/T > A/A) (n = 17) occurring outside of LOH regions (yellow circle, green box) and inside LOH regions (yellow circle, white box). DOI: http://dx.doi.org/10.7554/eLife.00662.014CC BY · PubMed Central
Figure 5—figure supplement 1. Co-occurrence of nonsynonymous SNPs occurring in conjunction with a shift in MIC. (A) For each of the 166 recurrently mutated genes associated with a change in MIC, we constructed a patient-by-gene binary vector. We clustered the resulting patient by gene matrix using NMF clustering to reveal 5 coherent clusters (correlation matrix of the clusters left; red: positive correlation; blue: negative correlation; white: no correlation). (B) Co-occurrence clusters. For the genes in each cluster (rows), shown are their mutated occurrences in each patient (columns); green: gene is persistently mutated in patient, white: no persistent mutation. Functional enrichment of clusters was revealed using gene ontology, and genes matching the enriched cluster function are bolded. DOI: http://dx.doi.org/10.7554/eLife.00662.015
Figure 5—figure supplement 1. Co-occurrence of nonsynonymous SNPs occurring in conjunction with a shift in MIC. (A) For each of the 166 recurrently mutated genes associated with a change in MIC, we constructed a patient-by-gene binary vector. We clustered the resulting patient by gene matrix using NMF clustering to reveal 5 coherent clusters (correlation matrix of the clusters left; red: positive correlation; blue: negative correlation; white: no correlation). (B) Co-occurrence clusters. For the genes in each cluster (rows), shown are their mutated occurrences in each patient (columns); green: gene is persistently mutated in patient, white: no persistent mutation. Functional enrichment of clusters was revealed using gene ontology, and genes matching the enriched cluster function are bolded. DOI: http://dx.doi.org/10.7554/eLife.00662.015CC BY · PubMed Central
Figure 6. Filamentation, adhesion and virulence increase concurrently with fitness. For each pair of consecutive isolates (green preceding blue), shown are the fitness, adhesion, filamentation, and virulence in a worm model of infection (each described in ‘Materials and methods’). A subset of fitness values are duplicated from Figure 7A, with selection coefficient (s) shown on the Y-axis. A subset of adhesion values are plotted from Figure 6—source data 1, with Abs590 nm on the Y-axis. A subset of images showing filamentation on spider media are shown, with the full set found in Figure 6—figure supplement 1. For virulence, shown are Kaplan–Meier plots of survival rates from C.elegans infection with the specified C. albicans isolates (‘Materials and methods’). For each isolate pair, significant changes in virulence were observed between the two isolates (in all cases, p < 0.001, log-rank test), with three of the four evolved isolates being more virulent than their corresponding progenitor. (A) Patient 30 isolates 5106 and 5108; (B) Patient 43 isolates 1649 and 3034; (C) Patient 1 isolates 12 and 13; (D) Patient 59 isolates 3917 and 4617. DOI: http://dx.doi.org/10.7554/eLife.00662.017
Figure 6. Filamentation, adhesion and virulence increase concurrently with fitness. For each pair of consecutive isolates (green preceding blue), shown are the fitness, adhesion, filamentation, and virulence in a worm model of infection (each described in ‘Materials and methods’). A subset of fitness values are duplicated from Figure 7A, with selection coefficient (s) shown on the Y-axis. A subset of adhesion values are plotted from Figure 6—source data 1, with Abs590 nm on the Y-axis. A subset of images showing filamentation on spider media are shown, with the full set found in Figure 6—figure supplement 1. For virulence, shown are Kaplan–Meier plots of survival rates from C.elegans infection with the specified C. albicans isolates (‘Materials and methods’). For each isolate pair, significant changes in virulence were observed between the two isolates (in all cases, p < 0.001, log-rank test), with three of the four evolved isolates being more virulent than their corresponding progenitor. (A) Patient 30 isolates 5106 and 5108; (B) Patient 43 isolates 1649 and 3034; (C) Patient 1 isolates 12 and 13; (D) Patient 59 isolates 3917 and 4617. DOI: http://dx.doi.org/10.7554/eLife.00662.017CC BY · PubMed Central
Figure 6—figure supplement 1. Filamentation increases in many patient series. For several patient series, shown are the filamentation assay results after 7 days of growth on Spider Media (‘Materials and Methods’). These data, a subset of which is shown in Figure 6, demonstrate the heterogeneity seen between strains, as well as the general trend for filamentation to increase over time. DOI: http://dx.doi.org/10.7554/eLife.00662.018
Figure 6—figure supplement 1. Filamentation increases in many patient series. For several patient series, shown are the filamentation assay results after 7 days of growth on Spider Media (‘Materials and Methods’). These data, a subset of which is shown in Figure 6, demonstrate the heterogeneity seen between strains, as well as the general trend for filamentation to increase over time. DOI: http://dx.doi.org/10.7554/eLife.00662.018CC BY · PubMed Central
Figure 7. Emergence of increased drug resistance often coincides with reduction in fitness in the absence of drug, but an increase in the presence of drug. (A) For each patient (panel) shown is the fitness (‘Materials and methods’) of each strain (Y axis, mean ± STDV), ordered from the progenitor to evolved isolates (left to right, X axis). Fitness is calculated relative to an ENO1::YFP SC5314 reference isolate. The MIC of each strain is shown in the gray boxes on top (white: low; black: high, color bar at bottom). Green: isolates with aneuploidies; Blue: euploid isolates. (B) Shown is the mean difference between fitness in the absence and presence of drug (Y axis, error bars are ± STDV; n > 3) for isolates (X axis) that showed a decrease in fitness (Figure 7A) in the absence of drug concomitant with an increase in MIC (asterisks), and flanking isolates in Patient 1 and 59 (ordered from the progenitor to evolved isolates, left to right, X axis). The difference in fitness is calculated as the difference in selection coefficient (s, Y axis) between matching competition experiments in RPMI and those in RPMI with one half the MIC for fluconazole (Table 1) for each isolate tested (X axis). Negative values indicate that the strain had higher fitness in the presence of fluconazole vs assays without fluconazole. For each assay, the fluconazole-resistant isolate 4639 ENO1::YFP was used as the reference strain. DOI: http://dx.doi.org/10.7554/eLife.00662.020
Figure 7. Emergence of increased drug resistance often coincides with reduction in fitness in the absence of drug, but an increase in the presence of drug. (A) For each patient (panel) shown is the fitness (‘Materials and methods’) of each strain (Y axis, mean ± STDV), ordered from the progenitor to evolved isolates (left to right, X axis). Fitness is calculated relative to an ENO1::YFP SC5314 reference isolate. The MIC of each strain is shown in the gray boxes on top (white: low; black: high, color bar at bottom). Green: isolates with aneuploidies; Blue: euploid isolates. (B) Shown is the mean difference between fitness in the absence and presence of drug (Y axis, error bars are ± STDV; n > 3) for isolates (X axis) that showed a decrease in fitness (Figure 7A) in the absence of drug concomitant with an increase in MIC (asterisks), and flanking isolates in Patient 1 and 59 (ordered from the progenitor to evolved isolates, left to right, X axis). The difference in fitness is calculated as the difference in selection coefficient (s, Y axis) between matching competition experiments in RPMI and those in RPMI with one half the MIC for fluconazole (Table 1) for each isolate tested (X axis). Negative values indicate that the strain had higher fitness in the presence of fluconazole vs assays without fluconazole. For each assay, the fluconazole-resistant isolate 4639 ENO1::YFP was used as the reference strain. DOI: http://dx.doi.org/10.7554/eLife.00662.020CC BY · PubMed Central
Figure 8. Deletion mutants of recurrently mutated genes reveal changes in relative fitness. Shown is the fitness (‘Materials and methods’) for each deletion mutant strain and the corresponding wild-type strain (Y axis, mean ± STDV). The wild-type parental strain (SN250) is on the far left (red bar and dashed line). Fitness is calculated relative to an ENO1::YFP SC5314 reference isolate. Locus names are given for the mutant isolates (X axis). Asterisks denote statistical significance (* < 0.05, ** < 0.01, *** < 0.001, **** < 0.0001) by one-way ANOVA with Holm–Sidak correction for multiple comparisons. DOI: http://dx.doi.org/10.7554/eLife.00662.021
Figure 8. Deletion mutants of recurrently mutated genes reveal changes in relative fitness. Shown is the fitness (‘Materials and methods’) for each deletion mutant strain and the corresponding wild-type strain (Y axis, mean ± STDV). The wild-type parental strain (SN250) is on the far left (red bar and dashed line). Fitness is calculated relative to an ENO1::YFP SC5314 reference isolate. Locus names are given for the mutant isolates (X axis). Asterisks denote statistical significance (* < 0.05, ** < 0.01, *** < 0.001, **** < 0.0001) by one-way ANOVA with Holm–Sidak correction for multiple comparisons. DOI: http://dx.doi.org/10.7554/eLife.00662.021CC BY · PubMed Central
Author response image 1. Null distributions of (a) the expected number of persistent, recurrent non synonymous SNPs outside of LOH regions, and (b) persistent non-synonymous SNPs associated with MIC changes outside of LOH regions.
Author response image 1. Null distributions of (a) the expected number of persistent, recurrent non synonymous SNPs outside of LOH regions, and (b) persistent non-synonymous SNPs associated with MIC changes outside of LOH regions.CC BY · PubMed Central
Author response image 2. The results of three separate MCMC analyses based on differing priors for mutation rate are shown. This analysis is based only on SNPs from isolates of Patient 1.
Author response image 2. The results of three separate MCMC analyses based on differing priors for mutation rate are shown. This analysis is based only on SNPs from isolates of Patient 1.CC BY · PubMed Central

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  • It may state two separate claims as one. 51
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  • The paper relies on this without support.

    Fluconazole is fungistatic, such that many cells exposed to the drug arrest their growth but do not die.

    “First, fluconazole, the antifungal drug used to treat the patients in our series, is fungistatic, such that many cells exposed to the drug arrest their growth but do not die.”
  • The paper relies on this without support.

    C. albicans is a highly heterozygous diploid whereas C. glabrata is haploid.

    “Second, C. albicans is a highly heterozygous diploid whereas C. glabrata is haploid.”
  • The paper relies on this without support.

    The culture medium used for in vitro fitness assays approximates in vivo conditions.

    “5 of the 22 deletion mutants reduced in vitro fitness in a culture medium thought to approximate in vivo conditions (Figure 8, ‘Materials and methods’).”
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Metadata

Authors
Ford, C. B., Funt, J. M., Abbey, D., Issi, L., Guiducci, C., Martinez, D. A., Delorey, T., Li, B. Y., White, T. C., Cuomo, C., Rao, R. P., Berman, J., Thompson, D. A., & Regev, A.
Affiliations
  • Broad Institute (US)
  • University of Minnesota (US)
  • Worcester Polytechnic Institute (US)
  • University of Missouri–Kansas City (US)
Corresponding author
  • Thompson, Dawn A
  • Regev, Aviv
Venue
eLife
Published
2015-02-03
Volume
4
Pages
e00662-e00662
ISSN
2050-084X (ISSN-L)
OpenAlex
W2089758228
Cited by
348
References
91
Citations by year
2026: 15 · 2025: 32 · 2024: 26 · 2023: 36 · 2022: 30 · 2021: 35 · 2020: 30 · 2019: 39 · 2018: 39 · 2017: 38 · 2016: 15 · 2015: 12
FWCI
26.99
Type
journal article
Language
en
Open access
Locations
  • eLife (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Digital WPI (submittedVersion, cc-by)
  • DSpace@MIT (Massachusetts Institute of Technology) (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
  • National Science Foundation (Graduate Student Fellowship)
  • Howard Hughes Medical Institute (Full investigator)
  • Helen Hay Whitney Foundation (Postdoctoral Fellowship)
  • National Institutes of Health (8DP1CA174427, 2R01CA119176-01)
  • Alfred P. Sloan Foundation
Topics
  • Health Sciences › Medicine › Infectious Diseases › Antifungal resistance and susceptibility
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Fungal and yeast genetics research
  • Life Sciences › Immunology and Microbiology › Microbiology › Yeasts and Rust Fungi Studies
Keywords
Candida albicans, drug resistance, azole resistance, ergosterol biosynthesis, oral candidiasis, loss of heterozygosity, copy number variation, single nucleotide polymorphisms, aneuploidy, host adaptation, fungal virulence, filamentation, cell adhesion, clinical isolates
MeSH terms
Adhesiveness, Aneuploidy, Candida albicans, Candidiasis, Humans, Microbial Sensitivity Tests, Mutation, Phenotype, Virulence, Fluconazole, Genome, Human, Sequence Analysis, DNA, Evolution, Molecular, Loss of Heterozygosity, Polymorphism, Single Nucleotide, Drug Resistance, Fungal, Host-Pathogen Interactions, Genetic Fitness

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

A language model drew the claims from the paper on 2026-10-09, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).

A second model labelled each claim on 2026-10-09 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).

Cited sources are checked with a language model’s help (gpt-6-sol).

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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