Genetic Analysis of Candida auris Implicates Hsp90 in Morphogenesis and Azole Tolerance and Cdr1 in Azole Resistance

ABSTRACT Candida auris is an emerging fungal pathogen and a serious global health threat as the majority of clinical isolates display elevated resistance to currently available antifungal drugs. Despite the increased prevalence of C. auris infections, the mechanisms governing drug resistance remain largely elusive. In diverse fungi, the evolution of drug resistance is enabled by the essential molecular chaperone Hsp90, which stabilizes key regulators of cellular responses to drug-induced stress. Hsp90 also orchestrates temperature-dependent morphogenesis in Candida albicans, a key virulence trait. However, the role of Hsp90 in the pathobiology of C. auris remains unknown. In order to study regulatory functions of Hsp90 in C. auris, we placed HSP90 under the control of a doxycycline-repressible promoter to enable transcriptional repression. We found that Hsp90 is essential for growth in C. auris and that it enables tolerance of clinical isolates with respect to the azoles, which inhibit biosynthesis of the membrane sterol ergosterol. High-level azole resistance was independent of Hsp90 but dependent on the ABC transporter CDR1, deletion of which resulted in abrogated resistance. Strikingly, we discovered that C. auris undergoes a morphogenetic transition from yeast to filamentous growth in response to HSP90 depletion or cell cycle arrest but not in response to other cues that induce C. albicans filamentation. Finally, we observed that this developmental transition is associated with global transcriptional changes, including the induction of cell wall-related genes. Overall, this report provides a novel insight into mechanisms of drug tolerance and resistance in C. auris and describes a developmental transition in response to perturbation of a core regulator of protein homeostasis. IMPORTANCE Fungal pathogens pose a serious threat to public health. Candida auris is an emerging fungal pathogen that is often resistant to commonly used antifungal drugs. However, the mechanisms governing drug resistance and virulence in this organism remain largely unexplored. In this study, we adapted a conditional expression system to modulate the transcription of an essential gene, HSP90, which regulates antifungal resistance and virulence in diverse fungal pathogens. We showed that Hsp90 is essential for growth in C. auris and is important for tolerance of the clinically important azole antifungals, which block ergosterol biosynthesis. Further, we established that the Cdr1 efflux transporter regulates azole resistance. Finally, we discovered that C. auris transitions from yeast to filamentous growth in response to Hsp90 inhibition, accompanied by global transcriptional remodeling. Overall, this work provides a novel insight into mechanisms regulating azole resistance in C. auris and uncovers a distinct developmental program regulated by Hsp90.

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Adenylyl Cyclase and Protein Kinase A Play Redundant and Distinct Roles in Growth, Differentiation, Antifungal Drug Resistance, and Pathogenicity of Candida auris

mBio ◽

10.1128/mbio.02729-21 ◽

2021 ◽

Author(s):

Ji-Seok Kim ◽

Kyung-Tae Lee ◽

Myung Ha Lee ◽

Eunji Cheong ◽

Yong-Sun Bahn

Keyword(s):

Drug Resistance ◽

Protein Kinase ◽

Protein Kinase A ◽

Fungal Pathogen ◽

Fungal Pathogens ◽

Antifungal Drugs ◽

Candida Auris ◽

Content Type ◽

Antifungal Drug Resistance ◽

Kinase A

Despite the recently growing concern of pan-resistant Candida auris infection, the pathogenicity of this ascomycetous fungal pathogen and the signaling circuitries governing its resistance to antifungal drugs are largely unknown. Therefore, we analyzed the pathobiological functions of cyclic AMP (cAMP)/protein kinase A (PKA) signaling pathway in C. auris , which plays conserved roles in the growth and virulence of fungal pathogens.

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Antimicrobial Octapeptin C4 Analogues Active against Cryptococcus Species

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00986-17 ◽

2017 ◽

Vol 62 (2) ◽

Cited By ~ 2

Author(s):

Jessica L. Chitty ◽

Mark S. Butler ◽

Azzah Suboh ◽

David J. Edwards ◽

Matthew A. Cooper ◽

...

Keyword(s):

Fungal Pathogen ◽

Antifungal Drugs ◽

Clinical Isolates ◽

Content Type ◽

Human Fungal Pathogen ◽

Cyclic Lipopeptide ◽

Structure Activity ◽

Cryptococcus Species ◽

Insight Into ◽

Better Than

ABSTRACTResistance to antimicrobials is a growing problem in both developed and developing countries. In nations where AIDS is most prevalent, the human fungal pathogenCryptococcus neoformansis a significant contributor to mortality, and its growing resistance to current antifungals is an ever-expanding threat. We investigated octapeptin C4, from the cationic cyclic lipopeptide class of antimicrobials, as a potential new antifungal. Octapeptin C4 was a potent, selective inhibitor of this fungal pathogen with an MIC of 1.56 μg/ml. Further testing of octapeptin C4 against 40 clinical isolates ofC. neoformansvar.grubiiorneoformansshowed an MIC of 1.56 to 3.13 μg/ml, while 20 clinical isolates ofC. neoformansvar.gattiihad an MIC of 0.78 to 12.5 μg/ml. In each case, the MIC values for octapeptin C4 were equivalent to, or better than, current antifungal drugs fluconazole and amphotericin B. The negatively charged polysaccharide capsule ofC. neoformansinfluences the pathogen's sensitivity to octapeptin C4, whereas the degree of melanization had little effect. Testing synthetic octapeptin C4 derivatives provided insight into the structure activity relationships, revealing that the lipophilic amino acid moieties are more important to the activity than the cationic diaminobutyric acid groups. Octapeptins have promising potential for development as anticryptococcal therapeutic agents.

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Staurosporine Induces Filamentation in the Human Fungal Pathogen Candida albicans via Signaling through Cyr1 and Protein Kinase A

mSphere ◽

10.1128/msphere.00056-17 ◽

2017 ◽

Vol 2 (2) ◽

Cited By ~ 12

Author(s):

Jinglin L. Xie ◽

Teresa R. O’Meara ◽

Elizabeth J. Polvi ◽

Nicole Robbins ◽

Leah E. Cowen

Keyword(s):

Candida Albicans ◽

Small Molecules ◽

Fungal Pathogen ◽

Fungal Pathogens ◽

Bloodstream Infections ◽

Filamentous Growth ◽

Genetic Pathways ◽

Content Type ◽

Virulence Trait ◽

The Impact

ABSTRACT The impact of fungal pathogens on human health is devastating. One of the most pervasive fungal pathogens is Candida albicans, which kills ~40% of people suffering from bloodstream infections. Treatment of these infections is extremely difficult, as fungi are closely related to humans, and there are limited drugs that kill the fungus without host toxicity. The capacity of C. albicans to transition between yeast and filamentous forms is a key virulence trait. Thus, understanding the genetic pathways that regulate morphogenesis could provide novel therapeutic targets to treat C. albicans infections. Here, we establish the small molecule staurosporine as an inducer of filamentous growth. We unveil distinct regulatory circuitry required for staurosporine-induced filamentation that appears to be unique to this filament-inducing cue. Thus, this work highlights the fact that small molecules, such as staurosporine, can improve our understanding of the pathways required for key virulence programs, which may lead to the development of novel therapeutics. Protein kinases are key regulators of signal transduction pathways that participate in diverse cellular processes. In fungal pathogens, kinases regulate signaling pathways that govern drug resistance, stress adaptation, and pathogenesis. The impact of kinases on the fungal regulatory circuitry has recently garnered considerable attention in the opportunistic fungal pathogen Candida albicans, which is a leading cause of human morbidity and mortality. Complex regulatory circuitry governs the C. albicans morphogenetic transition between yeast and filamentous growth, which is a key virulence trait. Here, we report that staurosporine, a promiscuous kinase inhibitor that abrogates fungal drug resistance, also influences C. albicans morphogenesis by inducing filamentation in the absence of any other inducing cue. We further establish that staurosporine exerts its effect via the adenylyl cyclase Cyr1 and the cyclic AMP (cAMP)-dependent protein kinase A (PKA). Strikingly, filamentation induced by staurosporine does not require the known upstream regulators of Cyr1, Ras1 or Pkc1, or effectors downstream of PKA, including Efg1. We further demonstrate that Cyr1 is capable of activating PKA to enable filamentation in response to staurosporine through a mechanism that does not require degradation of the transcriptional repressor Nrg1. We establish that staurosporine-induced filamentation is accompanied by a defect in septin ring formation, implicating cell cycle kinases as potential staurosporine targets underpinning this cellular response. Thus, we establish staurosporine as a chemical probe to elucidate the architecture of cellular signaling governing fungal morphogenesis and highlight the existence of novel circuitry through which the Cyr1 and PKA govern a key virulence trait. IMPORTANCE The impact of fungal pathogens on human health is devastating. One of the most pervasive fungal pathogens is Candida albicans, which kills ~40% of people suffering from bloodstream infections. Treatment of these infections is extremely difficult, as fungi are closely related to humans, and there are limited drugs that kill the fungus without host toxicity. The capacity of C. albicans to transition between yeast and filamentous forms is a key virulence trait. Thus, understanding the genetic pathways that regulate morphogenesis could provide novel therapeutic targets to treat C. albicans infections. Here, we establish the small molecule staurosporine as an inducer of filamentous growth. We unveil distinct regulatory circuitry required for staurosporine-induced filamentation that appears to be unique to this filament-inducing cue. Thus, this work highlights the fact that small molecules, such as staurosporine, can improve our understanding of the pathways required for key virulence programs, which may lead to the development of novel therapeutics.

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Multi-omics Signature of Candida auris, an Emerging and Multidrug-Resistant Pathogen

mSystems ◽

10.1128/msystems.00257-19 ◽

2019 ◽

Vol 4 (4) ◽

Cited By ~ 20

Author(s):

Daniel Zamith-Miranda ◽

Heino M. Heyman ◽

Levi G. Cleare ◽

Sneha P. Couvillion ◽

Geremy C. Clair ◽

...

Keyword(s):

Drug Resistance ◽

Protein Content ◽

Pathogenic Fungus ◽

Multidrug Resistant ◽

Antifungal Resistance ◽

Clinical Isolates ◽

Medical Mycology ◽

Carbon Utilization ◽

Candida Auris ◽

Content Type

ABSTRACT Candida auris is a recently described pathogenic fungus that is causing invasive outbreaks on all continents. The fungus is of high concern given the numbers of multidrug-resistant strains that have been isolated in distinct sites across the globe. The fact that its diagnosis is still problematic suggests that the spreading of the pathogen remains underestimated. Notably, the molecular mechanisms of virulence and antifungal resistance employed by this new species are largely unknown. In the present work, we compared two clinical isolates of C. auris with distinct drug susceptibility profiles and a Candida albicans reference strain using a multi-omics approach. Our results show that, despite the distinct drug resistance profile, both C. auris isolates appear to be very similar, albeit with a few notable differences. However, compared to C. albicans both C. auris isolates have major differences regarding their carbon utilization and downstream lipid and protein content, suggesting a multifactorial mechanism of drug resistance. The molecular profile displayed by C. auris helps to explain the antifungal resistance and virulence phenotypes of this new emerging pathogen. IMPORTANCE Candida auris was first described in Japan in 2009 and has now been the cause of significant outbreaks across the globe. The high number of isolates that are resistant to one or more antifungals, as well as the high mortality rates from patients with bloodstream infections, has attracted the attention of the medical mycology, infectious disease, and public health communities to this pathogenic fungus. In the current work, we performed a broad multi-omics approach on two clinical isolates isolated in New York, the most affected area in the United States and found that the omic profile of C. auris differs significantly from C. albicans. In addition to our insights into C. auris carbon utilization and lipid and protein content, we believe that the availability of these data will enhance our ability to combat this rapidly emerging pathogenic yeast.

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A Novel, Drug Resistance-Independent, Fluorescence-Based Approach To Measure Mutation Rates in Microbial Pathogens

mBio ◽

10.1128/mbio.00120-19 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 6

Author(s):

Erika Shor ◽

Jessica Schuyler ◽

David S. Perlin

Keyword(s):

Drug Resistance ◽

Mutation Rate ◽

Fungal Pathogen ◽

Candida Glabrata ◽

Drug Tolerance ◽

Clinical Isolates ◽

Mutation Rates ◽

Mismatch Repair Gene ◽

Repair Gene ◽

Content Type

ABSTRACT All evolutionary processes are underpinned by a cellular capacity to mutate DNA. To identify factors affecting mutagenesis, it is necessary to compare mutation rates between different strains and conditions. Drug resistance-based mutation reporters are used extensively to measure mutation rates, but they are suitable only when the compared strains have identical drug tolerance levels—a condition that is not satisfied under many “real-world” circumstances, e.g., when comparing mutation rates among a series of environmental or clinical isolates. Candida glabrata is a fungal pathogen that shows a high degree of genetic diversity and fast emergence of antifungal drug resistance. To enable meaningful comparisons of mutation rates among C. glabrata clinical isolates, we developed a novel fluorescence-activated cell sorting-based approach to measure the mutation rate of a chromosomally integrated GFP gene. We found that in Saccharomyces cerevisiae this approach recapitulated the reported mutation rate of a wild-type strain and the mutator phenotype of a shu1Δ mutant. In C. glabrata, the GFP reporter captured the mutation rate increases caused either by a genotoxic agent or by deletion of DNA mismatch repair gene MSH2, as well as the specific mutational signature associated with msh2Δ. Finally, the reporter was used to measure the mutation rates of C. glabrata clinical isolates carrying different alleles of MSH2. Together, these results show that fluorescence-based mutation reporters can be used to measure mutation rates in microbes under conditions of unequal drug susceptibility to reveal new insights about drivers of mutagenesis. IMPORTANCE Measurements of mutation rates—i.e., how often proliferating cells acquire mutations in their DNA—are essential for understanding cellular processes that maintain genome stability. Many traditional mutation rate measurement assays are based on detecting mutations that cause resistance to a particular drug. Such assays typically work well for laboratory strains but have significant limitations when comparing clinical or environmental isolates that have various intrinsic levels of drug tolerance, which confounds the interpretation of results. Here we report the development and validation of a novel method of measuring mutation rates, which detects mutations that cause loss of fluorescence rather than acquisition of drug resistance. Using this method, we measured the mutation rates of clinical isolates of fungal pathogen Candida glabrata. This assay can be adapted to other organisms and used to compare mutation rates in contexts where unequal drug sensitivity is anticipated.

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Targeting Methionine Synthase in a Fungal Pathogen Causes a Metabolic Imbalance That Impacts Cell Energetics, Growth, and Virulence

mBio ◽

10.1128/mbio.01985-20 ◽

2020 ◽

Vol 11 (5) ◽

Author(s):

Jennifer Scott ◽

Monica Sueiro-Olivares ◽

Benjamin P. Thornton ◽

Rebecca A. Owens ◽

Howbeer Muhamadali ◽

...

Keyword(s):

Beneficial Effect ◽

Aspergillus Fumigatus ◽

Fungal Pathogen ◽

Fungal Pathogens ◽

Antifungal Drugs ◽

New Drugs ◽

Methionine Synthase ◽

Content Type ◽

Metabolic Imbalance

ABSTRACT There is an urgent need to develop novel antifungals to tackle the threat fungal pathogens pose to human health. Here, we have performed a comprehensive characterization and validation of the promising target methionine synthase (MetH). We show that in Aspergillus fumigatus the absence of this enzymatic activity triggers a metabolic imbalance that causes a reduction in intracellular ATP, which prevents fungal growth even in the presence of methionine. Interestingly, growth can be recovered in the presence of certain metabolites, which shows that metH is a conditionally essential gene and consequently should be targeted in established infections for a more comprehensive validation. Accordingly, we have validated the use of the tetOFF genetic model in fungal research and improved its performance in vivo to achieve initial validation of targets in models of established infection. We show that repression of metH in growing hyphae halts growth in vitro, which translates into a beneficial effect when targeting established infections using this model in vivo. Finally, a structure-based virtual screening of methionine synthases reveals key differences between the human and fungal structures and unravels features in the fungal enzyme that can guide the design of novel specific inhibitors. Therefore, methionine synthase is a valuable target for the development of new antifungals. IMPORTANCE Fungal pathogens are responsible for millions of life-threatening infections on an annual basis worldwide. The current repertoire of antifungal drugs is very limited and, worryingly, resistance has emerged and already become a serious threat to our capacity to treat fungal diseases. The first step to develop new drugs is often to identify molecular targets in the pathogen whose inhibition during infection can prevent its growth. However, the current models are not suitable to validate targets in established infections. Here, we have characterized the promising antifungal target methionine synthase in great detail, using the prominent fungal pathogen Aspergillus fumigatus as a model. We have uncovered the underlying reason for its essentiality and confirmed its druggability. Furthermore, we have optimized the use of a genetic system to show a beneficial effect of targeting methionine synthase in established infections. Therefore, we believe that antifungal drugs to target methionine synthase should be pursued and additionally, we provide a model that permits gaining information about the validity of antifungal targets in established infections.

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Drug-Resistant Epimutants Exhibit Organ-Specific Stability and Induction during Murine Infections Caused by the Human Fungal Pathogen Mucor circinelloides

mBio ◽

10.1128/mbio.02579-19 ◽

2019 ◽

Vol 10 (6) ◽

Cited By ~ 51

Author(s):

Zanetta Chang ◽

Joseph Heitman

Keyword(s):

Drug Resistance ◽

Murine Model ◽

Fungal Pathogen ◽

Fungal Pathogens ◽

Antifungal Agents ◽

Mucor Circinelloides ◽

Antifungal Resistance ◽

Content Type ◽

The Brain

ABSTRACT The environmentally ubiquitous fungus Mucor circinelloides is a primary cause of the emerging disease mucormycosis. Mucor infection is notable for causing high morbidity and mortality, especially in immunosuppressed patients, while being inherently resistant to the majority of clinically available antifungal drugs. A new, RNA interference (RNAi)-dependent, and reversible epigenetic mechanism of antifungal resistance—epimutation—was recently discovered in M. circinelloides. However, the effects of epimutation in a host-pathogen setting were unknown. We employed a systemic, intravenous murine model of Mucor infection to elucidate the potential impact of epimutation in vivo. Infection with an epimutant strain resistant to the antifungal agents FK506 and rapamycin revealed that the epimutant-induced drug resistance was stable in vivo in a variety of different organs and tissues. Reversion of the epimutant-induced drug resistance was observed to be more rapid in isolates from the brain than in isolates recovered from the liver, spleen, kidney, or lungs. Importantly, infection with a wild-type strain of Mucor led to increased rates of epimutation after strains were recovered from organs and exposed to FK506 stress in vitro. Once again, this effect was more pronounced in strains recovered from the brain than from other organs. In summary, we report the rapid induction and reversion of RNAi-dependent drug resistance after in vivo passage through a murine model, with pronounced impact in strains recovered from brain. Defining the role played by epimutation in drug resistance and infection advances our understanding of Mucor and other fungal pathogens and may have implications for antifungal therapy. IMPORTANCE The emerging fungal pathogen Mucor circinelloides causes a severe infection, mucormycosis, which leads to considerable morbidity and mortality. Treatment of Mucor infection is challenging because Mucor is inherently resistant to nearly all clinical antifungal agents. An RNAi-dependent and reversible mechanism of antifungal resistance, epimutation, was recently reported for Mucor. Epimutation has not been studied in vivo, and it was unclear whether it would contribute to antifungal resistance observed clinically. We demonstrate that epimutation can both be induced and reverted after in vivo passage through a mouse; rates of both induction and reversion are higher after brain infection than after infection of other organs (liver, spleen, kidneys, or lungs). Elucidating the roles played by epimutation in drug resistance and infection will improve our understanding of Mucor and other fungal pathogens and may have implications for antifungal treatment.

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Pseudohyphal Growth of the Emerging Pathogen Candida auris Is Triggered by Genotoxic Stress through the S Phase Checkpoint

mSphere ◽

10.1128/msphere.00151-20 ◽

2020 ◽

Vol 5 (2) ◽

Cited By ~ 6

Author(s):

Gustavo Bravo Ruiz ◽

Zoe K. Ross ◽

Neil A. R. Gow ◽

Alexander Lorenz

Keyword(s):

Fungal Pathogens ◽

Genotoxic Stress ◽

Multidrug Resistant ◽

S Phase ◽

Antifungal Drugs ◽

Yeast Cells ◽

Candida Auris ◽

Content Type ◽

Pseudohyphal Growth ◽

S Phase Checkpoint

ABSTRACT The morphogenetic switching between yeast cells and filaments (true hyphae and pseudohyphae) is a key cellular feature required for full virulence in many polymorphic fungal pathogens, such as Candida albicans. In the recently emerged yeast pathogen Candida auris, occasional elongation of cells has been reported. However, environmental conditions and genetic triggers for filament formation have remained elusive. Here, we report that induction of DNA damage and perturbation of replication forks by treatment with genotoxins, such as hydroxyurea, methyl methanesulfonate, and the clinically relevant fungistatic 5-fluorocytosine, cause filamentation in C. auris. The filaments formed were characteristic of pseudohyphae and not parallel-sided true hyphae. Pseudohyphal growth is apparently signaled through the S phase checkpoint and, interestingly, is Tup1 independent in C. auris. Intriguingly, the morphogenetic switching capability is strain specific in C. auris, highlighting the heterogenous nature of the species as a whole. IMPORTANCE Candida auris is a newly emerged fungal pathogen of humans. This species was first reported in 2009 when it was identified in an ear infection of a patient in Japan. However, despite intense interest in this organism as an often multidrug-resistant fungus, there is little knowledge about its cellular biology. During infection of human patients, fungi are able to change cell shape from ellipsoidal yeast cells to elongated filaments to adapt to various conditions within the host organism. There are different types of filaments, which are triggered by reactions to different cues. Candida auris fails to form filaments when exposed to triggers that stimulate yeast filament morphogenesis in other fungi. Here, we show that it does form filaments when its DNA is damaged. These conditions might arise when Candida auris cells interact with host immune cells or during growth in certain host tissues (kidney or bladder) or during treatment with antifungal drugs.

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Hog1 Regulates Stress Tolerance and Virulence in the Emerging Fungal PathogenCandida auris

mSphere ◽

10.1128/msphere.00506-18 ◽

2018 ◽

Vol 3 (5) ◽

Cited By ~ 18

Author(s):

Alison M. Day ◽

Megan M. McNiff ◽

Alessandra da Silva Dantas ◽

Neil A. R. Gow ◽

Janet Quinn

Keyword(s):

Protein Kinase ◽

Stress Resistance ◽

Fungal Pathogen ◽

Antifungal Drugs ◽

Control Measures ◽

Emerging Pathogen ◽

Candida Auris ◽

Content Type ◽

Resistance Profile

ABSTRACTCandida aurishas recently emerged as an important, multidrug-resistant fungal pathogen of humans. Comparative studies indicate that despite high levels of genetic divergence,C. aurisis as virulent as the most pathogenic member of the genus,Candida albicans. However, key virulence attributes ofC. albicans, such as morphogenetic switching, are not utilized byC. auris, indicating that this emerging pathogen employs alternative strategies to infect and colonize the host. An important trait required for the pathogenicity of many fungal pathogens is the ability to adapt to host-imposed stresses encountered during infection. Here, we investigated the relative resistance ofC. aurisand other pathogenicCandidaspecies to physiologically relevant stresses and explored the role of the evolutionarily conserved Hog1 stress-activated protein kinase (SAPK) in promoting stress resistance and virulence. In comparison toC. albicans,C. aurisis relatively resistant to hydrogen peroxide, cationic stress, and cell-wall-damaging agents. However, in contrast to otherCandidaspecies examined,C. auris was unable to grow in an anaerobic environment and was acutely sensitive to organic oxidative-stress-inducing agents. An analysis ofC. aurishog1Δ cells revealed multiple roles for this SAPK in stress resistance, cell morphology, aggregation, and virulence. These data demonstrate thatC. aurishas a unique stress resistance profile compared to those of other pathogenicCandidaspecies and that the Hog1 SAPK has pleiotropic roles that promote the virulence of this emerging pathogen.IMPORTANCEThe rapid global emergence and resistance ofCandidaauristo current antifungal drugs highlight the importance of understanding the virulence traits exploited by this human fungal pathogen to cause disease. Here, we characterize the stress resistance profile ofC. aurisand the role of the Hog1 stress-activated protein kinase (SAPK) in stress resistance and virulence. Our findings thatC. aurisis acutely sensitive to certain stresses may facilitate control measures to prevent persistent colonization in hospital settings. Furthermore, our observation that the Hog1 SAPK promotesC. aurisvirulence akin to that reported for many other pathogenic fungi indicates that antifungals targeting Hog1 signaling would be broad acting and effective, even on emerging drug-resistant pathogens.

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Species Identification andIn VitroAntifungal Susceptibility ofAspergillus terreusSpecies Complex Clinical Isolates from a French Multicenter Study

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02315-17 ◽

2018 ◽

Vol 62 (5) ◽

pp. e02315-17 ◽

Cited By ~ 4

Author(s):

S. Imbert ◽

A. C. Normand ◽

S. Ranque ◽

J. M. Costa ◽

J. Guitard ◽

...

Keyword(s):

Amphotericin B ◽

Antifungal Susceptibility ◽

Sensu Stricto ◽

Antifungal Drugs ◽

Clinical Isolates ◽

Clinical Samples ◽

Azole Resistance ◽

University Hospitals ◽

Content Type ◽

Interesting Alternative

ABSTRACTAspergillussectionTerreiis a species complex currently comprised of 14 cryptic species whose prevalence in clinical samples as well as antifungal susceptibility are poorly known. The aims of this study were to investigateA. Terreiclinical isolates at the species level and to perform antifungal susceptibility analyses by reference and commercial methods. Eighty-two clinicalA. Terreiisolates were collected from 8 French university hospitals. Molecular identification was performed by sequencing parts of beta-tubulin and calmodulin genes. MICs or minimum effective concentrations (MECs) were determined for 8 antifungal drugs using both EUCAST broth microdilution (BMD) methods and concentration gradient strips (CGS). Among the 79A. Terreiisolates,A. terreus stricto sensu(n= 61),A. citrinoterreus(n= 13),A. hortai(n= 3), andA. alabamensis(n= 2) were identified. All strains had MICs of ≥1 mg/liter for amphotericin B, except for two isolates (bothA. hortai) that had MICs of 0.25 mg/liter. FourA. terreusisolates were resistant to at least one azole drug, including one with pan-azole resistance, yet no mutation in theCYP51Agene was found. All strains had low MECs for the three echinocandins. The essential agreements (EAs) between BMD and CGS were >90%, except for those of amphotericin B (79.7%) and itraconazole (73.4%). Isolates belonging to theA. sectionTerreiidentified in clinical samples show wider species diversity beyond the knownA. terreus sensu stricto. Azole resistance inside the sectionTerreiis uncommon and is not related to CYP51A mutations here. Finally, CGS is an interesting alternative for routine antifungal susceptibility testing.

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