Evaluation of CHROMagar Candida Plus for the detection of C. auris with a panel of 206 fungal isolates and 83 colonization screening skin-swabs.

CHROMagar Candida Plus is a new formulation of chromogenic media designed for the detection and differentiation of major clinical Candida species, including Candida auris. The objective of this study is to evaluate CHROMagar Candida Plus when used according to manufacturer's instructions with a panel of 206 fungal isolates and 83 skin-swab specimens originally collected for C. auris colonization screening. Of the 68 C. auris isolates tested, 66/68 displayed the expected light-blue colony morphology and blue halo within 48 h. None of the remaining 138 non-auris isolates appeared similar to C. auris. CHROMagarCandida Plus was, therefore, inclusive to 97% of 68 C. auris isolates tested and supported visual exclusion of 100% of the 138 non-C. auris isolates tested. For the 83 colonization screening specimens, direct plating onto CHROMagarCandida Plus was 60% sensitive and 100% specific when compared to the enrichment broth gold-standard reference method. In sum, these findings demonstrate the utility of this media when working with isolates but also notable limitations when working with primary skin-swabs specimens when competing yeast species are present.IMPORTANCECandida auris is an emerging fungal pathogen of public health concern. As it continues to spread, it is important to publish evaluations of new diagnostic tools. In this study, we share our experience with a new chromogenic media which can help distinguish C. auris from related species.

Fungal Pathogens as Causes of Acute Respiratory Illness in Hospitalized Veterans: Frequency of Fungal Positive Test Results Using Rapid Immunodiagnostic Assays.

Fungal respiratory illnesses caused by endemic mycoses can be nonspecific and are often mistaken for viral or bacterial infections. We performed fungal testing on serum specimens from patients hospitalized with acute respiratory illness (ARI) to assess the possible role of endemic fungi as etiologic agents. Patients hospitalized with ARI at a Veterans Affairs hospital in Houston, Texas, during November 2016-August 2017 were enrolled. Epidemiologic and clinical data, nasopharyngeal and oropharyngeal samples for viral testing (PCR), and serum specimens were collected at admission. We retrospectively tested remnant sera from a subset of patients with negative initial viral testing using immunoassays for the detection of Coccidioides and Histoplasma antibodies (Ab) and Cryptococcus, Aspergillus, and Histoplasma antigens (Ag). Of 224 patient serum specimens tested, 49 (22%) had positive results for fungal pathogens, including 30 (13%) by Coccidioides immunodiagnostic assays, 19 (8%) by Histoplasma immunodiagnostic assays, 2 (1%) by Aspergillus Ag, and none by Cryptococcus Ag testing. A high proportion of veterans hospitalized with ARI had positive serological results for fungal pathogens, primarily endemic mycoses, which cause fungal pneumonia. The high proportion of Coccidioides positivity is unexpected as this fungus is not thought to be common in southeastern Texas or metropolitan Houston, though is known to be endemic in southwestern Texas. Although serological testing suffers from low specificity, these results suggest that these fungi may be more common causes of ARI in southeast Texas than commonly appreciated and more increased clinical evaluation may be warranted.

Whole-genome sequencing of Candida haemulonii species complex from Brazil and the United States: Genetic diversity and antifungal susceptibility.

Candida haemulonii complex species can be multidrug-resistant and cause infections such as candidemia. This study determined the genetic relationship between isolates from Brazil and the United States through whole-genome sequencing and performed antifungal susceptibility testing to investigate drug resistance. Contrary to what is widely described, most isolates were susceptible to azoles. However, an atypical susceptibility profile was found in 50% of Candida pseudohaemulonii strains, including resistance to the three echinocandins. Isolates from both countries formed distinct clusters with wide genetic diversity. Isolates from three hospitals in Brazil were clonal and involved in candidemia cases, pointing to the importance of improving hospital infection control measures and molecular identification.

Candida haemulonii complex species is worldwide distributed, and this study aimed to evaluate the resistance to antifungal drugs in cases from Brazil and the United States, and also compare their genetic relationships. A total of 50 strains were studied; most of them from Brazil were from cases of bloodstream infections, while the strains from the United States came from cases of wounds and may be associated with diabetic patients. The vast majority of strains were resistant to amphotericin B, one of the most effective drugs, and susceptible to fluconazole. In addition, 50% of C. pseudohaemulonii strains were resistant to echinocandins. The strains from Brazil and the United States had no genetic relationship and formed two distinct groups. In three Brazilian hospitals, strains were clonal, indicating an intra-hospital transmission. Our findings contribute to guiding therapy in bloodstream fungal infections caused by C. haemulonii species and alerting for nosocomial transmission of this yeast complex species.

In Vitro Activity of the Novel Antifungal Olorofim against Scedosporium and Lomentospora prolificans.

Scedosporium spp. and Lomentospora prolificans are an emerging group of fungi refractory to current antifungal treatments. These species largely affect immunocompromised individuals but can also be lung colonizers in cystic fibrosis patients. Although Scedosporium apiospermum is thought to be the predominant species, the group has been expanded to a species complex. The distribution of species within the S. apiospermum species complex and other closely related species in the United States is largely unknown. Here, we used ß-tubulin and ITS sequences to identify 37 Scedosporium isolates to the species level. These Scedosporium isolates as well as 13 L. prolificans isolates were tested against a panel of nine antifungal drugs, including the first in novel class orotimide, olorofim. IMPORTANCE Scedosporium and Lomentospora infections are notoriously hard to treat as these organisms can be resistant to numerous antifungals. The manuscript contributes to our knowledge of the activity of the new antifungal agent olorofim and comparator agents against Lomentospora and against Scedosporium isolates that have been molecularly identified to the species level. The efficacy of olorofim against all species of Scedosporium and Lomentospora was confirmed.

Genomic description of human clinical Aspergillus fumigatus isolates, California, 2020.

Aspergillus fumigatus, an environmental mold, causes life-threatening infections. Studies on the phylogenetic structure of human clinical A. fumigatus isolates are limited. Here, we performed whole genome sequencing of 24 A. fumigatus isolates collected from 18 patients in U.S. healthcare facilities in California. Single-nucleotide polymorphism (SNP) differences between patient isolates ranged from 187 to 70 829 SNPs. For five patients with multiple isolates, we calculated the within-host diversities. Three patients had a within-host diversity that ranged from 4 to 10 SNPs and two patients ranged from 2 to 16 977 SNPs. Findings revealed highly diverse A. fumigatus strains among patients and two patterns of diversity for isolates that come from the same patient, low and extremely high diversity.

Aspergillus fumigatus is an environmental mold. It can cause a severe infection called aspergillosis in patients with weakened immune systems. We analyzed A. fumigatus DNA from patients at California hospitals. We described genetic diversity between samples from the same patients and among different patients. Our findings provide insight on using genomic sequencing to investigate aspergillosis in hospitals.

Molecular Epidemiology of Blastomyces gilchristii Clusters, Minnesota, USA.

We characterized 2 clusters of blastomycosis cases in Minnesota, USA, using whole-genome sequencing and single-nucleotide polymorphism analyses. Blastomyces gilchristii was confirmed as the cause of infection. Genomic analyses corresponded with epidemiologic findings for cases of B. gilchristii infections, demonstrating the utility of genomic methods for future blastomycosis outbreak investigations.

Clinical Characteristics, Health Care Utilization, and Outcomes Among Patients in a Pilot Surveillance System for Invasive Mold Disease-Georgia, United States, 2017-2019.

Background: Invasive mold diseases (IMDs) cause severe illness, but public health surveillance data are lacking. We describe data collected from a laboratory-based, pilot IMD surveillance system. Methods: During 2017-2019, the Emerging Infections Program conducted active IMD surveillance at 3 Atlanta-area hospitals. We ascertained potential cases by reviewing histopathology, culture, and Aspergillus galactomannan results and classified patients as having an IMD case (based on European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group [MSG] criteria) or a non-MSG IMD case (based on the treating clinician's diagnosis and use of mold-active antifungal therapy). We described patient features and compared patients with MSG vs non-MSG IMD cases. Results: Among 304 patients with potential IMD, 104 (34.2%) met an IMD case definition (41 MSG, 63 non-MSG). The most common IMD types were invasive aspergillosis (n = 66 [63.5%]), mucormycosis (n = 8 [7.7%]), and fusariosis (n = 4 [3.8%]); the most frequently affected body sites were pulmonary (n = 66 [63.5%]), otorhinolaryngologic (n = 17 [16.3%]), and cutaneous/deep tissue (n = 9 [8.7%]). Forty-five (43.3%) IMD patients received intensive care unit-level care, and 90-day all-cause mortality was 32.7%; these outcomes did not differ significantly between MSG and non-MSG IMD patients. Conclusions: IMD patients had high mortality rates and a variety of clinical presentations. Comprehensive IMD surveillance is needed to assess emerging trends, and strict application of MSG criteria for surveillance might exclude over one-half of clinically significant IMD cases.

Candida parapsilosis Mdr1B and Cdr1B Are Drivers of Mrr1-Mediated Clinical Fluconazole Resistance.

Candida parapsilosis is a common cause of invasive candidiasis worldwide and is the most commonly is7olated Candida species among pediatric and neonatal populations. Previous work has demonstrated that nonsynonymous mutations in the gene encoding the putative transcription factor CpMrr1 can influence fluconazole susceptibility. However, the direct contribution of these mutations and how they influence fluconazole resistance in clinical isolates are poorly understood. We identified 7 nonsynonymous CpMRR1 mutations in 12 isolates from within a collection of 35 fluconazole-resistant clinical isolates. The mutations leading to the A854V, R479K, and I283R substitutions were further examined and found to be activating mutations leading to increased fluconazole resistance. In addition to CpMDR1, we identified two other genes, one encoding a major facilitator superfamily (MFS) transporter (CpMDR1B, CPAR2_603010) and one encoding an ATP-binding cassette (ABC) transporter (CpCDR1B, CPAR2_304370), as being upregulated in isolates carrying CpMRR1-activating mutations. Overexpression of CpMDR1 in a susceptible strain and disruption in resistant clinical isolates that overexpress CpMDR1 had little to no effect on fluconazole susceptibility. Conversely, overexpression of either CpMDR1B or CpCDR1B increased resistance, and disruption in clinical isolates overexpressing these genes decreased fluconazole resistance. Our findings suggest that activating mutations in CpMRR1 represent important genetic determinants of fluconazole resistance in clinical isolates of C. parapsilosis, and unlike what is observed in Candida albicans, this is primarily driven by upregulation of both MFS (CpMdr1B) and ABC (CpCdr1B) transporters.

Rapid Assessment and Containment of Candida auris Transmission in Postacute Care Settings-Orange County, California, 2019.

BACKGROUND: Candida auris, a multidrug-resistant yeast, can spread rapidly in ventilator-capable skilled-nursing facilities (vSNFs) and long-term acute care hospitals (LTACHs). In 2018, a laboratory serving LTACHs in southern California began identifying species of Candida that were detected in urine specimens to enhance surveillance of C auris, and C auris was identified in February 2019 in a patient in an Orange County (OC), California, LTACH. Further investigation identified C auris at 3 associated facilities. OBJECTIVE: To assess the prevalence of C auris and infection prevention and control (IPC) practices in LTACHs and vSNFs in OC. DESIGN: Point prevalence surveys (PPSs), postdischarge testing for C auris detection, and assessments of IPC were done from March to October 2019. SETTING: All LTACHs (n = 3) and vSNFs (n = 14) serving adult patients in OC. PARTICIPANTS: Current or recent patients in LTACHs and vSNFs in OC. INTERVENTION: In facilities where C auris was detected, PPSs were repeated every 2 weeks. Ongoing IPC support was provided. MEASUREMENTS: Antifungal susceptibility testing and whole-genome sequencing to assess isolate relatedness. RESULTS: Initial PPSs at 17 facilities identified 44 additional patients with C auris in 3 (100%) LTACHs and 6 (43%) vSNFs, with the first bloodstream infection reported in May 2019. By October 2019, a total of 182 patients with C auris were identified by serial PPSs and discharge testing. Of 81 isolates that were sequenced, all were clade III and highly related. Assessments of IPC identified gaps in hand hygiene, transmission-based precautions, and environmental cleaning. The outbreak was contained to 2 facilities by October 2019. LIMITATION: Acute care hospitals were not assessed, and IPC improvements over time could not be rigorously evaluated. CONCLUSION: Enhanced laboratory surveillance and prompt investigation with IPC support enabled swift identification and containment of C auris. PRIMARY FUNDING SOURCE: Centers for Disease Control and Prevention.

Genomic Diversity of Azole-Resistant Aspergillus fumigatus in the United States.

Azole resistance in pathogenic Aspergillus fumigatus has become a global public health issue threatening the use of medical azoles. The environmentally occurring resistance mutations, TR34/L98H (TR34) and TR46/Y121F/T289A (TR46), are widespread across multiple continents and emerging in the United States. We used whole-genome single nucleotide polymorphism (SNP) analysis on 179 nationally represented clinical and environmental A. fumigatus genomes from the United States along with 18 non-U.S. genomes to evaluate the genetic diversity and foundation of the emergence of azole resistance in the United States. We demonstrated the presence of clades of A. fumigatus isolates: clade A (17%) comprised a global collection of clinical and environmental azole-resistant strains, including all strains with the TR34/L98H allele from India, The Netherlands, the United Kingdom, and the United States, and clade B (83%) consisted of isolates without this marker mainly from the United States. The TR34/L98H polymorphism was shared among azole-resistant A. fumigatus strains from India, The Netherlands, the United Kingdom, and the United States, suggesting the common origin of this resistance mechanism. Six percent of azole-resistant A. fumigatus isolates from the United States with the TR34 resistance marker had a mixture of clade A and clade B alleles, suggestive of recombination. Additionally, the presence of equal proportions of both mating types further suggests the ongoing presence of recombination. This study demonstrates the genetic background for the emergence of azole resistance in the United States, supporting a single introduction and subsequent propagation, possibly through recombination of environmentally driven resistance mutations. IMPORTANCE Aspergillus fumigatus is one of the most common causes of invasive mold infections in patients with immune deficiencies and has also been reported in patients with severe influenza and severe acute respiratory syndrome coronavirus 2 (SARs-CoV-2). Triazole drugs are the first line of therapy for this infection; however, their efficacy has been compromised by the emergence of azole resistance in A. fumigatus, which was proposed to be selected for by exposure to azole fungicides in the environment [P. E. Verweij, E. Snelders, G. H. J. Kema, E. Mellado, et al., Lancet Infect Dis 9:789-795, 2009, https://doi.org/10.1016/S1473-3099(09)70265-8]. Isolates with environmentally driven resistance mutations, TR34/L98H (TR34) and TR46/Y121F/T289A (TR46), have been reported worldwide. Here, we used genomic analysis of a large sample of resistant and susceptible A. fumigatus isolates to demonstrate a single introduction of TR34 in the United States and suggest its ability to spread into the susceptible population is through recombination between resistant and susceptible isolates.

In Vitro Activity of Novel Antifungal Olorofim against Filamentous Fungi and Comparison to Eight Other Antifungal Agents.

Olorofim is a novel antifungal drug that belongs to the orotomide drug class which inhibits fungal dihydroorotate dehydrogenase (DHODH), thus halting pyrimidine biosynthesis and ultimately DNA synthesis, cell growth and division. It is being developed at a time when many invasive fungal infections exhibit antifungal resistance or have limited treatment options. The goal of this study was to evaluate the in vitro effectiveness of olorofim against a large collection of recently isolated, clinically relevant American mold isolates. In vitro antifungal activity was determined for 246 azole-susceptible Aspergillus fumigatus isolates, five A. fumigatus with TR34/L98H-mediated resistance, 19 Rhizopus species isolates, 21 Fusarium species isolates, and one isolate each of six other species of molds. Olorofim minimum inhibitory concentrations (MICs) were compared to antifungal susceptibility testing profiles for amphotericin B, anidulafungin, caspofungin, isavuconazole, itraconazole, micafungin, posaconazole, and voriconazole. Olorofim MICs were significantly lower than those of the echinocandin and azole drug classes and amphotericin B. A. fumigatus wild type and resistant isolates shared the same MIC50 = 0.008 µg/mL. In non-Aspergillus susceptible isolates (MIC ≤ 2 µg/mL), the geometric mean (GM) MIC to olorofim was 0.54 µg/mL with a range of 0.015-2 µg/mL. Olorofim had no antifungal activity (MIC ≥ 2 µg/mL) against 10% of the collection (31 in 297), including some isolates from Rhizopus spp. and Fusarium spp. Olorofim showed promising activity against A. fumigatus and other molds regardless of acquired azole resistance.

Antifungal activity of nikkomycin Z against Candida auris.

BACKGROUND: Nikkomycin Z is a competitive inhibitor of chitin synthase-an enzyme needed for synthesis of the fungal cell wall. Nikkomycin Z shows promise as a treatment for coccidioidomycoses and mixed activity has been described against other fungi and yeast. To our knowledge, it has not previously been tested against the emerging fungal pathogen Candida auris. OBJECTIVES: To determine the in vitro activity of nikkomycin Z against C. auris. METHODS: Nikkomycin Z was tested by broth microdilution against a panel of 100 isolates of genetically diverse C. auris from around the world. RESULTS: Nikkomycin Z showed mixed activity against the tested isolates, with an MIC range of 0.125 to >64 mg/L. The MIC50 and MIC90 were 2 and 32 mg/L, respectively. CONCLUSIONS: These findings suggest nikkomycin Z has in vitro activity against some, but not all isolates of C. auris.

Categorizing Susceptibility of Clinical Isolates of Candida auris to Amphotericin B, Caspofungin, and Fluconazole by Use of the CLSI M44-A2 Disk Diffusion Method.

We evaluated the CLSI M44ed3E disk diffusion method compared with the CLSI M27ed4 broth microdilution method for caspofungin and fluconazole and the Etest method for amphotericin B to categorize susceptibility of 347 clinical isolates of Candida auris Utilizing the zone diameter cutoffs established here, we observed overall categorical agreement between the two methods. For caspofungin, concordant results were observed for 98% of isolates, with <1% very major and 1% major errors. For fluconazole, concordant results were observed for 91% of isolates, with 1% very major and 8% major errors. For amphotericin B, concordant results were observed for 74% of isolates, with <1% very major errors and 25% major errors. The disk diffusion approach provides an accurate method for determining the susceptibility of C. auris for caspofungin and fluconazole and for identification of at least 75% of amphotericin B-susceptible isolates.

Bloodstream Infections With Candida auris Among Children in Colombia: Clinical Characteristics and Outcomes of 34 Cases.

BACKGROUND: Candida auris is an emerging multidrug-resistant yeast that can cause invasive infections and healthcare-associated outbreaks. Here, we describe 34 cases of pediatric C. auris bloodstream infections (BSIs) identified during July 2014-October 2017 in 2 hospitals in Colombia. METHODS: We conducted a retrospective review of microbiology records for possible C. auris cases in 2 hospitals in Barranquilla and Cartagena. BSIs that occurred in patients aged <18 years confirmed as C. auris were included in this analysis. RESULTS: We identified 34 children with C. auris BSIs. Twenty-two (65%) patients were male, 21% were aged <28 days, 47% were aged 29-365 days, and 32% were aged >1 year. Underlying conditions included preterm birth (26%), being malnourished (59%), cancer (12%), solid-organ transplant (3%), and renal disease (3%). Eighty-two percent had a central venous catheter (CVC), 82% were on respiratory support, 56% received total parenteral nutrition (TPN), 15% had a surgical procedure, and 9% received hemodialysis. Preinfection inpatient stay was 22 days (interquartile range, 19-33 days), and in-hospital mortality was 41%. CONCLUSIONS: Candida auris affects children with a variety of medical conditions including prematurity and malignancy, as well as children with CVCs and those who receive TPN. Mortality was high, with nearly half of patients dying before discharge. However, unlike most other Candida species, C. auris can be transmitted in healthcare settings, as suggested by the close clustering of cases in time at each of the hospitals.Candida auris is an emerging multidrug-resistant yeast that can cause invasive infections and healthcare-associated outbreaks. This report describes 34 cases of pediatric C. auris bloodstream infections, identified in two hospitals in Colombia, South America.

Ibrexafungerp: A Novel Oral Triterpenoid Antifungal in Development for the Treatment of Candida auris Infections.

Candida auris is an emerging multidrug-resistant fungal pathogen reported worldwide. Infections due to C. auris are usually nosocomial and associated with high rates of fluconazole resistance and mortality. Echinocandins are utilized as the first-line treatment. However, echinocandins are only available intravenously and are associated with increasingly higher rates of resistance by C. auris. Thus, a need exists for novel treatments that demonstrate potent activity against C. auris. Ibrexafungerp is a first-in-class triterpenoid antifungal agent. Similar to echinocandins, ibrexafungerp inhibits (1→3)-ß-D-glucan synthase, a key component of the fungal cell wall, resulting in fungicidal activity against Candida spp. Ibrexafungerp demonstrates broad in vitro activity against various Candida spp. including C. auris and C. auris isolates with fks mutations. Minimum inhibitory concentration (MIC50 and MIC90) values in >400 C. auris isolates were 0.5 µg/mL and 1.0 µg/mL, respectively. Clinical results were reported for two patients with invasive candidiasis or candidemia due to C. auris treated during the CARES (Candidiasis Caused by Candida Auris) trial, an ongoing open-label study. These patients experienced a complete response after treatment with ibrexafungerp. Thus, ibrexafungerp represents a promising new antifungal agent for treating C. auris infections.

Evaluation of nine surface disinfectants against Candida auris using a quantitative disk carrier method: EPA SOP-MB-35.

We tested 9 disinfectants against Candida auris using the quantitative disk carrier method EPA-MB-35-00: 5 products with hydrogen peroxide or alcohol-based chemistries were effective and 4 quaternary ammonium compound-based products were not. This work supported a FIFRA Section 18 emergency exemption granted by the US Environmental Protection Agency to expand disinfectant guidance for C. auris.

Understanding the Emergence of Multidrug-Resistant Candida: Using Whole-Genome Sequencing to Describe the Population Structure of Candida haemulonii Species Complex.

The recent emergence of a multidrug-resistant yeast, Candida auris, has drawn attention to the closely related species from the Candida haemulonii complex that include C. haemulonii, Candida duobushaemulonii, Candida pseudohaemulonii, and the recently identified Candida vulturna. Here, we used antifungal susceptibility testing and whole-genome sequencing (WGS) to investigate drug resistance and genetic diversity among isolates of C. haemulonii complex from different geographic areas in order to assess population structure and the extent of clonality among strains. Although most isolates of all four species were genetically distinct, we detected evidence of the in-hospital transmission of C. haemulonii and C. duobushaemulonii in one hospital in Panama, indicating that these species are also capable of causing outbreaks in healthcare settings. We also detected evidence of the rising azole resistance among isolates of C. haemulonii and C. duobushaemulonii in Colombia, Panama, and Venezuela linked to substitutions in ERG11 gene as well as amplification of this gene in C. haemulonii in isolates in Colombia suggesting the presence of evolutionary pressure for developing azole resistance in this region. Our results demonstrate that these species need to be monitored as possible causes of outbreaks of invasive infection.

Mutations in TAC1B: a Novel Genetic Determinant of Clinical Fluconazole Resistance in Candida auris.

Candida auris has emerged as a multidrug-resistant pathogen of great clinical concern. Approximately 90% of clinical C. auris isolates are resistant to fluconazole, the most commonly prescribed antifungal agent, and yet it remains unknown what mechanisms underpin this fluconazole resistance. To identify novel mechanisms contributing to fluconazole resistance in C. auris, fluconazole-susceptible C. auris clinical isolate AR0387 was passaged in media supplemented with fluconazole to generate derivative strains which had acquired increased fluconazole resistance in vitro Comparative analyses of comprehensive sterol profiles, [3H]fluconazole uptake, sequencing of C. auris genes homologous to genes known to contribute to fluconazole resistance in other species of Candida, and relative expression levels of C. aurisERG11, CDR1, and MDR1 were performed. All fluconazole-evolved derivative strains were found to have acquired mutations in the zinc-cluster transcription factor-encoding gene TAC1B and to show a corresponding increase in CDR1 expression relative to the parental clinical isolate, AR0387. Mutations in TAC1B were also identified in a set of 304 globally distributed C. auris clinical isolates representing each of the four major clades. Introduction of the most common mutation found among fluconazole-resistant clinical isolates of C. auris into fluconazole-susceptible isolate AR0387 was confirmed to increase fluconazole resistance by 8-fold, and the correction of the same mutation in a fluconazole-resistant isolate, AR0390, decreased fluconazole MIC by 16-fold. Taken together, these data demonstrate that C. auris can rapidly acquire resistance to fluconazole in vitro and that mutations in TAC1B significantly contribute to clinical fluconazole resistance.IMPORTANCECandida auris is an emerging multidrug-resistant pathogen of global concern, known to be responsible for outbreaks on six continents and to be commonly resistant to antifungals. While the vast majority of clinical C. auris isolates are highly resistant to fluconazole, an essential part of the available antifungal arsenal, very little is known about the mechanisms contributing to resistance. In this work, we show that mutations in the transcription factor TAC1B significantly contribute to clinical fluconazole resistance. These studies demonstrated that mutations in TAC1B can arise rapidly in vitro upon exposure to fluconazole and that a multitude of resistance-associated TAC1B mutations are present among the majority of fluconazole-resistant C. auris isolates from a global collection and appear specific to a subset of lineages or clades. Thus, identification of this novel genetic determinant of resistance significantly adds to the understanding of clinical antifungal resistance in C. auris.

Antifungal Susceptibility Testing: Current Approaches.

Although not as ubiquitous as antibacterial susceptibility testing, antifungal susceptibility testing (AFST) is a tool of increasing importance in clinical microbiology laboratories. The goal of AFST is to reliably produce MIC values that may be used to guide patient therapy, inform epidemiological studies, and track rates of antifungal drug resistance. There are three methods that have been standardized by standards development organizations: broth dilution, disk diffusion, and azole agar screening for Aspergillus Other commonly used methods include gradient diffusion and the use of rapid automated instruments. Novel methodologies for susceptibility testing are in development. It is important for laboratories to consider not only the method of testing but also the interpretation (or lack thereof) of in vitro data.