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Cited by 95Antifungal resistance and susceptibilityFungal and yeast genetics researchFungal Plant Pathogen Control

Multidrug transporters and alterations in sterol biosynthesis contribute to azole antifungal resistance in Candida parapsilosis

Open access
Berkow, Elizabeth L., Manigaba, Kayihura, Parker, Josie E., Barker, Katherine S., Kelly, Stephen L., Rogers, P. David·2015·Antimicrobial Agents and Chemotherapy
DOI 10.1128/aac.01358-15PMC PMC4576097
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Abstract

While much is known concerning azole resistance in Candida albicans , considerably less is understood about Candida parapsilosis , an emerging species of Candida with clinical relevance. We conducted a comprehensive analysis of azole resistance in a collection of resistant C. parapsilosis clinical isolates in order to determine which genes might play a role in this process within this species. We examined the relative expression of the putative drug transporter genes CDR1 and MDR1 and that of ERG11 . In isolates overexpressing these genes, we sequenced the genes encoding their presumed transcriptional regulators, TAC1 , MRR1 , and UPC2 , respectively. We also sequenced the sterol biosynthesis genes ERG3 and ERG11 in these isolates to find mutations that might contribute to this phenotype in this Candida species. Our findings demonstrate that the putative drug transporters Cdr1 and Mdr1 contribute directly to azole resistance and suggest that their overexpression is due to activating mutations in the genes encoding their transcriptional regulators. We also observed that the Y132F substitution in ERG11 is the only substitution occurring exclusively among azole-resistant isolates, and we correlated this with specific changes in sterol biosynthesis. Finally, sterol analysis of these isolates suggests that other changes in sterol biosynthesis may contribute to azole resistance in C. parapsilosis .

AI snapshot

Written from the paper’s full text.

TL;DR

In a collection of 35 fluconazole-resistant and 4 susceptible *Candida parapsilosis* clinical isolates, overexpression of *CDR1*/*MDR1* and *ERG11* plus the *ERG11* Y132F substitution were associated with azole resistance, but deleting *CDR1* or *MDR1* only reduced fluconazole MICs by one dilution. Known resistance mechanisms did not fully explain the high-level azole resistance observed.

Key findings

  • Among 35 fluconazole-resistant isolates, fluconazole MICs ranged from 8 to 256 μg/ml; the 4 susceptible isolates had MICs of 0.5 μg/ml. Voriconazole susceptibility varied: 14 susceptible, 13 susceptible dose dependent, and 12 resistant (MICs 1–8 μg/ml); itraconazole MICs ranged from 0.016 to 0.5 μg/ml.
  • *CDR1* was overexpressed ≥2-fold in 16 isolates (fluconazole MIC ≥16 μg/ml), *MDR1* was overexpressed ≥25-fold in isolates 29, 30, and 36 (fluconazole MIC ≥64 μg/ml), and *ERG11* was overexpressed ≥2-fold in 8 isolates (fluconazole MIC 16–128 μg/ml; isolate 27 had the highest, 11-fold, MIC 32 μg/ml).
  • Deleting *CDR1* in isolates 35, 38, and 40 produced a 1-dilution fluconazole MIC decrease (128→64, 256→128, and 128→64 μg/ml, respectively), with reversion on complementation; deleting *MDR1* in isolates 30 and 36 also produced a 1-dilution decrease (128→64 and 64→32 μg/ml), while isolate 29 showed no change (64 μg/ml).
  • No *ERG3* mutations were found. *ERG11* substitutions S216L, Y132F, and R398I occurred in 16 isolates; Y132F occurred only in resistant isolates (alone in 1, with R398I in 10), and 9 of 11 Y132F-containing isolates had measurable 14-methyl fecosterol plus high lanosterol/obtusifoliol. *TAC1* substitutions (G650E in 35 and 38; L978W in 40) and *MRR1* substitutions (A854V in 29, R479K in 30, I283R in 36) did not correspond to documented activating mutations; only isolate 36 had a heterozygous *UPC2* mutation.

Methods

  • The study analyzed 35 unrelated fluconazole-resistant and 4 susceptible *C. parapsilosis* clinical isolates from the University of Iowa, plus constructed deletion/complementation strains; azole MICs were determined by CLSI M27-A3 broth microdilution.
  • Relative expression of *CDR1*, *MDR1*, and *ERG11* was measured by quantitative RT-PCR (2−ΔΔCT), and *TAC1*, *MRR1*, *UPC2*, *ERG3*, and *ERG11* were sequenced in relevant isolates; *CDR1* and *MDR1* were deleted and complemented in selected overexpressing isolates.
  • Sterol profiles were obtained by GC-MS after nonsaponifiable lipid extraction and TMS derivatization.

Limitations

  • The paper states that known molecular mechanisms do not completely account for the azole resistance observed and that there is still insufficient cause for the high-level resistance in numerous isolates; it also states that the direct role of the *TAC1* and *MRR1* SNPs in activating transcription remains to be determined and that the significance of several sterol-profile alterations is unknown.
  • The paper notes no interpretive guidelines exist for itraconazole susceptibility testing of *C. parapsilosis*, and that the reference strain CDC317 itself contains Y132F with a fluconazole MIC of 4 μg/ml.
  • Evident from the text: only 4 susceptible isolates served as controls; no functional validation is reported for the *UPC2* mutation; no *ERG2* sequencing was done despite a sterol profile suggesting possible Erg2 impairment; and *MDR1* deletion phenotypes were not reported as complemented, whereas *CDR1* phenotypes were.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1128/aac.01358-15

Cites

Statistics

Nothing to recompute.

Claims the paper makes

0 of 12 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    The 35 fluconazole-resistant Candida parapsilosis isolates exhibited fluconazole MICs ranging from 8 to 256 μg/ml.

    “The 35 resistant isolates exhibited MICs for fluconazole ranging from 8 to 256 μg/ml.”
    Quote in the paperNot a substantial claim
  • Findingown data

    The susceptibilities of all Candida parapsilosis isolates to itraconazole ranged from 0.016 to 0.5 μg/ml.

    “The susceptibilities of all isolates to itraconazole ranged from 0.016 to 0.5 μg/ml.”
    Quote in the paperNot a substantial claim
  • Findingown data

    All phenotypes reverted upon complementation of the deleted CDR1 alleles.

    “All phenotypes reverted upon complementation of the deleted alleles.”
    Quote in the paperSubstantial claim
  • Findingown data

    The Y132F substitution in ERG11 correlates with specific changes in sterol biosynthesis in Candida parapsilosis isolates.

    “and we correlated this with specific changes in sterol biosynthesis.”
    Quote in the paperSubstantial claim
  • Findingown data

    The 16 CDR1-overexpressing Candida parapsilosis isolates exhibited a fluconazole MIC of ≥16 μg/ml.

    “These isolates exhibited a fluconazole MIC of ≥16 μg/ml.”
    Quote in the paperSubstantial claim
  • May combine two claims. 17
  • Classified as probably not a substantial claim. 12
  • The quote only partly states this claim. 1

  • May combine two claims.

    Findingown data

    Isolates 29, 30, and 36 each exhibited a fluconazole MIC of ≥64 μg/ml.

    “each exhibited an MIC of fluconazole of ≥64 μg/ml.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The fluconazole MIC for isolates 35 and 40 dropped from 128 μg/ml to 64 μg/ml, and that for isolate 38 dropped from 256 μg/ml to 128 μg/ml upon CDR1 deletion.

    “The fluconazole MIC for isolates 35 and 40 both dropped from 128 μg/ml to 64 μg/ml, and that for isolate 38 dropped from 256 μg/ml to 128 μg/ml.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Isolate 29 contained an A854V substitution, isolate 30 contained an R479K substitution, and isolate 36 contained an I283R substitution in MRR1.

    “Isolate 29 contained an A854V substitution, isolate 30 contained an R479K substitution, and isolate 36 contained an I283R substitution.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Isolate 27 exhibited the highest ERG11 expression level, with an 11-fold increase.

    “Notably, a single isolate (isolate 27) exhibited the highest expression level, with an 11-fold increase.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The four susceptible Candida parapsilosis isolates had fluconazole MICs of 0.5 μg/ml and none were susceptible dose dependent.

    “As expected, the four remaining isolates were susceptible to fluconazole, with MICs of 0.5 μg/ml, and none were susceptible dose dependent.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Of the 39 total Candida parapsilosis isolates, 14 were susceptible to voriconazole, 13 were susceptible dose dependent, and 12 were resistant, with voriconazole MICs ranging from 1 to 8 μg/ml.

    “Of the 39 total isolates, 14 isolates were susceptible to voriconazole, 13 were susceptible dose dependent, and the remaining 12 isolates were resistant to voriconazole, with MICs ranging from 1 to 8 μg/ml.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Among resistant Candida parapsilosis isolates, expression of both drug transporter genes varied, with expression levels increased as much as 50-fold.

    “For the resistant isolates, we observed varied expression of both drug transporter genes among the isolates, with expression levels increased as much as 50-fold.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Isolates 35 and 38 contained the TAC1 amino acid substitution G650E, whereas isolate 40 contained a heterozygous L978W substitution.

    “Both isolates 35 and 38 contained the amino acid substitution G650E, whereas isolate 40 contained a heterozygous L978W substitution.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Isolates 22 and 37 have larger than average amounts of 4-methyl fecosterol, with slight decreases in ergosterol abundance.

    “Isolates 22 and 37 have larger than average amounts of 4-methyl fecosterol, with slight decreases in ergosterol abundance.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    The MIC of fluconazole for reference strain CDC317 is 4 μg/ml.

    “It is worthwhile to note that the *ERG11* sequence for the reference strain CDC317 contains the Y132F substitution in Erg11, and the MIC of fluconazole for this strain is 4 μg/ml.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Whereas ergosta-8-enol is detected in quite small quantities in most isolates, its level is relatively high in isolate 39.

    “Whereas ergosta-8-enol is detected in quite small quantities in most isolates, its level is relatively high in isolate 39.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Isolate 4 has a relatively normal ergosterol abundance but a high fecosterol abundance.

    “Isolate 4 has a relatively normal ergosterol abundance but a high fecosterol abundance.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Isolate 4 exhibited an increase in fecosterol in addition to an increase in ergosterol.

    “For example, isolates 4, 15, and 19 each exhibited increases in fecosterol, isolates 15 and 19 displayed higher than average levels of 4-methyl fecosterol, and isolate 4 exhibited an increase in fecosterol in addition to an increase in ergosterol.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The fluconazole MIC for isolate 30 dropped from 128 μg/ml to 64 μg/ml, and that for isolate 36 dropped from 64 μg/ml to 32 μg/ml upon MDR1 deletion.

    “The fluconazole MIC for isolate 30 dropped from 128 μg/ml to 64 μg/ml, and that for isolate 36 dropped from 64 μg/ml to 32 μg/ml.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Overexpression of the ABC transporters Cdr1 and Cdr2 results in efflux of all azole antifungals in Candida albicans.

    “Overexpression of the ATP binding cassette (ABC) transporters Cdr1 and Cdr2 results in the efflux of all azole antifungals”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [12] Sanglard D, Kuchler K, Ischer F, Pagani JL, Monod M, Bille J. 1995. Mechanisms of resistance to azole antifungal agents in Candida albicans isolates from AIDS patients involve specific multidrug transporters. Antimicrob Agents Chemother 39:2378–2386. doi: 10.1128/AAC.39.11.2378. [[DOI](https://doi.org/10.1128/AAC.39.11.2378)] [[PMC free article](/articles/PMC162951/)] [[PubMed](https://pubmed.ncbi.nlm.nih.gov/8585712/)] [[Google Scholar](https://scholar.google.com/scholar_lookup?journal=Antimicrob%20Agents%20Chemother&title=Mechanisms%20of%20resistance%20to%20azole%20antifungal%20agents%20in%2 source

      Not checked in the free run.

    • cites [13] Lopez-Ribot JL, McAtee RK, Lee LN, Kirkpatrick WR, White TC, Sanglard D, Patterson TF. 1998. Distinct patterns of gene expression associated with development of fluconazole resistance in serial Candida albicans isolates from human immunodeficiency virus-infected patients with oropharyngeal candidiasis. Antimicrob Agents Chemother 42:2932–2937. [[DOI](https://doi.org/10.1128/aac.42.11.2932)] [[PMC free article](/articles/PMC105968/)] [[PubMed](https://pubmed.ncbi.nlm.nih.gov/9797228/)] [[Google Scholar](https://scholar.google.com/scholar_lookup?journal=Antimicrob%20Agents%20Chemother&title=Dist

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductown data

    Two independent replicate mutant strains were created for each gene deletion, and MICs were determined according to CLSI guidelines.

    “Two independent replicate mutant strains were created for each, and MICs were determined according to CLSI guidelines.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [19] Clinical and Laboratory Standards Institute. 2008. Reference method for broth dilution antifungal susceptibility testing of yeasts; approved standard—3rd ed CLSI document M27-A3. Clinical and Laboratory Standards Institute, Wayne, PA. [[Google Scholar](https://scholar.google.com/scholar_lookup?title=CLSI%20document%20M27-A3&publication_year=2008&)]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Increases in 14-methyl fecosterol have been identified in Erg3-defective strains of C. albicans following Erg11 inhibition by azole treatment.

    “Increases in this sterol have been identified in Erg3-defective strains of *C. albicans* following Erg11 inhibition by azole treatment ([26](#B26)).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [26] Watson PF, Rose ME, Ellis SW, England H, Kelly SL. 1989. Defective sterol C5-6 desaturation and azole resistance: a new hypothesis for the mode of action of azole antifungals. Biochem Biophys Res Commun 164:1170–1175. doi: 10.1016/0006-291X(89)91792-0. [[DOI](https://doi.org/10.1016/0006-291X(89)91792-0)] [[PubMed](https://pubmed.ncbi.nlm.nih.gov/2556119/)] [[Google Scholar](https://scholar.google.com/scholar_lookup?journal=Biochem%20Biophys%20Res%20Commun&title=Defective%20sterol%20C5-6%20desaturation%20and%20azole%20resistance:%20a%20new%20hypothesis%20for%20the%20mode%20of%20action%20of%20a source

      Not checked in the free run.

  • The quote only partly states this claim.

    Interpretationown data

    This might indicate a bottleneck in the pathway around ERG25/26/27, leading to reduced ergosterol production in isolates 22 and 37.

    “This might indicate a bottleneck in the pathway around ERG25/26/27, leading to reduced ergosterol production.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    This might indicate a higher turnover through enzymes upstream of fecosterol and less rapid consumption/conversion through enzymes encoded by ERG2/3/4/5 in isolate 4.

    “This might indicate a higher turnover through the enzymes upstream of fecosterol and less rapid consumption/conversion through the enzymes encoded by ERG2/3/4/5 ([Fig. 3](#F3)).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    It is possible that weaker mutations fail to arise in the presence of azole concentrations achieved during the treatment of bloodstream infections.

    “It is possible that weaker mutations fail to arise in the presence of azole concentrations achieved during the treatment of bloodstream infections.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In C. albicans, deletion of CaMDR1 in resistant isolates overexpressing this gene led to only a 1-dilution decrease in fluconazole susceptibility.

    “For Mdr1, this observation is consistent with what has been observed in *C. albicans*, in which the deletion of Ca*MDR1* in resistant isolates overexpressing this gene led to only a 1-dilution decrease in fluconazole susceptibility ([14](#B14)).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [14] Morschhäuser J, Barker KS, Liu TT, BlaB-Warmuth J, Homayouni R, Rogers PD. 2007. The transcription factor Mrr1p controls expression of the MDR1 efflux pump and mediates multidrug resistance in Candida albicans. PLoS Pathog 3:e164. doi: 10.1371/journal.ppat.0030164. [[DOI](https://doi.org/10.1371/journal.ppat.0030164)] [[PMC free article](/articles/PMC2048531/)] [[PubMed](https://pubmed.ncbi.nlm.nih.gov/17983269/)] [[Google Scholar](https://scholar.google.com/scholar_lookup?journal=PLoS%20Pathog&title=The%20transcription%20factor%20Mrr1p%20controls%20expression%20of%20the%20MDR1%20efflux%20pump source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    The azole resistance mechanism of ERG3 alterations is uncommon in clinical isolates of C. albicans and may be concluded about C. parapsilosis.

    “This azole resistance mechanism is considered uncommon in clinical isolates of *C. albicans* and, according to this analysis, the same might be concluded about *C. parapsilosis*.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In C. albicans, deletion of CDR1 increases susceptibility to fluconazole to a greater degree.

    “We were, however, surprised that the deletion of *CDR1* in isolates overexpressing this gene did not increase susceptibility to fluconazole to a greater degree, as has been observed in *C. albicans* ([15](#B15)).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [15] Coste A, Turner V, Ischer F, Morschhäuser J, Forche A, Selmecki A, Berman J, Bille J, Sanglard D. 2006. A mutation in Tac1p, a transcription factor regulating CDR1 and CDR2, is coupled with loss of heterozygosity at chromosome 5 to mediate antifungal resistance in Candida albicans. Genetics 172:2139–2156. [[DOI](https://doi.org/10.1534/genetics.105.054767)] [[PMC free article](/articles/PMC1456413/)] [[PubMed](https://pubmed.ncbi.nlm.nih.gov/16452151/)] [[Google Scholar](https://scholar.google.com/scholar_lookup?journal=Genetics&title=A%20mutation%20in%20Tac1p,%20a%20transcription%20factor%20r source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    We previously found 26 distinct amino acid substitutions in a collection of 63 fluconazole-resistant C. albicans clinical isolates.

    “We previously found 26 distinct amino acid substitutions in a collection of 63 fluconazole-resistant *C. albicans* clinical isolates ([17](#B17)).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [17] Flowers SA, Colón B, Whaley SG, Schuler MA, Rogers PD. 2015. Contribution of clinically derived mutations in *ERG11* to azole resistance in Candida albicans. Antimicrob Agents Chemother 59:450–460. doi: 10.1128/AAC.03470-14. [[DOI](https://doi.org/10.1128/AAC.03470-14)] [[PMC free article](/articles/PMC4291385/)] [[PubMed](https://pubmed.ncbi.nlm.nih.gov/25385095/)] [[Google Scholar](https://scholar.google.com/scholar_lookup?journal=Antimicrob%20Agents%20Chemother&title=Contribution%20of%20clinically%20derived%20mutations%20in%20ERG11%20to%20azole%20resistance%20in%20Candida%20albicans&author= source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    It is possible that the Y132F mutation alters Erg11 such that its function is compromised, forcing higher sterol turnover at Erg25/Erg26/Erg27.

    “It is possible that Erg11 is altered in such a way by the Y132F mutation that the function of this enzyme has been compromised, forcing higher sterol turnover at the point of Erg25/Erg26/Erg27.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The R398I substitution occurred alone in 1 susceptible isolate (isolate 3) and does not appear to directly influence azole susceptibility.

    “The R398I substitution occurred alone in 1 susceptible isolate (isolate 3) and therefore does not appear to directly influence azole susceptibility.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    In C. albicans, alterations among genes in the ergosterol biosynthesis pathway contribute to changes in azole susceptibility.

    “In *C. albicans*, alterations among genes in the ergosterol biosynthesis pathway contribute to changes in azole susceptibility ([25](#B25)).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [25] White TC, Marr KA, Bowden RA. 1998. Clinical, cellular, and molecular factors that contribute to antifungal drug resistance. Clin Microbiol Rev 11:382–402. [[DOI](https://doi.org/10.1128/cmr.11.2.382)] [[PMC free article](/articles/PMC106838/)] [[PubMed](https://pubmed.ncbi.nlm.nih.gov/9564569/)] [[Google Scholar](https://scholar.google.com/scholar_lookup?journal=Clin%20Microbiol%20Rev&title=Clinical,%20cellular,%20and%20molecular%20factors%20that%20contribute%20to%20antifungal%20drug%20resistance&author=TC%20White&author=KA%20Marr&author=RA%20Bowden&volume=11&publication_year=1998&pages=382-4 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In C. albicans, the Y132F substitution was among the strongest individual mutations with regard to impact on fluconazole susceptibility, increasing the MIC of fluconazole from 0.5 μg/ml to 2 μg/ml.

    “Indeed, in *C. albicans*, the Y132F substitution was among the strongest individual mutations with regard to impact on fluconazole susceptibility, increasing the MIC of fluconazole from 0.5 μg/ml to 2 μg/ml ([17](#B17)).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [17] Flowers SA, Colón B, Whaley SG, Schuler MA, Rogers PD. 2015. Contribution of clinically derived mutations in *ERG11* to azole resistance in Candida albicans. Antimicrob Agents Chemother 59:450–460. doi: 10.1128/AAC.03470-14. [[DOI](https://doi.org/10.1128/AAC.03470-14)] [[PMC free article](/articles/PMC4291385/)] [[PubMed](https://pubmed.ncbi.nlm.nih.gov/25385095/)] [[Google Scholar](https://scholar.google.com/scholar_lookup?journal=Antimicrob%20Agents%20Chemother&title=Contribution%20of%20clinically%20derived%20mutations%20in%20ERG11%20to%20azole%20resistance%20in%20Candida%20albicans&author= source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationnone given

    It is likely that an individual isolate contains more than one mechanism.

    “Although it is likely that an individual isolate contains more than one mechanism, there is still insufficient cause for the high-level resistance observed for numerous isolates.”
    Quote in the paperNot a substantial claim
29 of 29

  • The paper relies on this without support.

    Mechanisms of azole resistance operative in clinical isolates of C. parapsilosis are similar to those observed in C. albicans.

    “We reasoned that mechanisms of azole resistance operative in clinical isolates of *C. parapsilosis* would be similar to those observed in *C. albicans*.”

  • The paper relies on this without support.

    ERG11 is overexpressed in azole-resistant C. albicans isolates.

    “As has been observed in *C. albicans*, *ERG11* was found to be overexpressed in many of the azole-resistant clinical *C. parapsilosis* isolates in this collection.”

  • The paper relies on this without support.

    For bloodstream infections, higher doses of azoles are used and higher concentrations at the site of infection are achieved than for oral infections.

    “whereas the *C. parapsilosis* isolates in this collection were bloodstream isolates, for which higher doses of azoles are used and higher concentrations at the site of infection are achieved.”

  • The paper relies on this without support.

    Many azole-resistant C. albicans isolates in which ERG11 mutations have been identified are oral isolates.

    “It is important to note that many azole-resistant *C. albicans* isolates in which *ERG11* mutations have been identified are oral isolates”

  • The paper relies on this without support.

    Amino acid position 132 is located in the predicted Erg11 catalytic site and most likely interacts with fluconazole.

    “Amino acid position 132 is located in the predicated Erg11 catalytic site and most likely interacts with fluconazole.”
5 of 5

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Resistance to azoles in C. parapsilosis has been attributed to mutations in MRR1 and ERG11 (Y132F alone or with R398I), and overexpression of CDR1, MDR1, and ERG11.

    “Resistance to azoles in C. parapsilosis has been attributed to mutations in the transcription factor gene MRR1 [84] and ERG11 (Y132F, either alone or in combination with an R398I) [85,86,87], and overexpression of CDR1, MDR1, and ERG11 [85,86,88].”

    From Evolutionary Emergence of Drug Resistance in Candida Opportunistic Pathogens (2018) · cites this paper as [86]

  • Overexpression of the azole target gene ERG11 has not always been associated with point mutations in its UPC2 regulator.

    “overexpression of the azole target gene ERG11 has not always been associated with point mutations in its UPC2 regulator [86,90,118]”

    From Evolutionary Emergence of Drug Resistance in Candida Opportunistic Pathogens (2018) · cites this paper as [86]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Y132F is reported as a difference from a reference strain that also carries Y132F

    Major

    The paper says it identified ERG11 substitutions by comparing isolate sequences with reference strain CDC317. It reports Y132F among those substitutions, but later says CDC317 itself contains Y132F, so Y132F cannot be a sequence difference from that reference.

  • Reported itraconazole range excludes a tabled MIC

    Minor

    The text gives 0.5 μg/ml as the highest itraconazole MIC, but Table 3 reports 1 μg/ml for isolate 30.

  • A reported decrease in susceptibility accompanies lower MICs

    Minor

    The stated decrease in fluconazole susceptibility conflicts with the reported decreases in MIC: lower MICs indicate greater susceptibility.

3 of 3

The citation lists haven’t been fetched yet

References 27 · Cited by 95

Research works printed but not linked: 1

  1. Clinical and Laboratory Standards Institute. 2008. Reference method for broth dilution antifungal susceptibility testing of yeasts; approved standard—3rd ed. CLSI document M27-A3. Clinical and Laboratory Standards Institute, Wayne, PA.

Authors
Berkow, E. L., Manigaba, K., Parker, J. E., Barker, K. S., Kelly, S. L., & Rogers, P. D.
Affiliations
  • University of Tennessee Health Science Center (US)
  • Swansea University (GB)
ORCID
Venue
Antimicrobial Agents and Chemotherapy
Publisher
American Society for Microbiology
Published
2015-10
Volume
59
Issue
10
Pages
5942-5950
ISSN
  • 0066-4804 (ISSN-L)
  • 1098-6596
DOI
10.1128/aac.01358-15
PMC
PMC4576097
OpenAlex
W1776905503
Semantic Scholar
863cae9383bb9e90f42e47af597743fff14083ca
Cited by
95
References
27
Citations by year
2026: 2 · 2025: 13 · 2024: 8 · 2023: 10 · 2022: 13 · 2021: 5 · 2020: 11 · 2019: 8 · 2018: 10 · 2017: 13 · 2016: 2
FWCI
6.48
Type
journal article
Language
en
Open access
Licence
journals.asm.org/non-commercial-tdm-license (tdm)
Locations
  • Antimicrobial Agents and Chemotherapy (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • National Institutes of Health
  • National Institute of Allergy and Infectious Diseases (R01AI058145)
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 › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Fungal Plant Pathogen Control
Keywords
Candida parapsilosis, azole resistance, multidrug transporter, CDR1, MDR1, ERG11, sterol biosynthesis, ERG3, transcription factors, TAC1, MRR1, UPC2, clinical isolates, drug efflux
MeSH terms
Antifungal Agents, Candida, Candidiasis, Fungal Proteins, Humans, Microbial Sensitivity Tests, Mutation, Oxidoreductases, Phenotype, Sterols, Transcription, Genetic, Trans-Activators, Fluconazole, Gene Expression Regulation, Fungal, Sequence Analysis, DNA, ATP-Binding Cassette Transporters, ATP Binding Cassette Transporter, Subfamily B, Member 1, Drug Resistance, Fungal, Sterol 14-Demethylase

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.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-09.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-09.

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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