Liposomal amphotericin B-the past.

The discovery of amphotericin B, a polyene antifungal compound, in the 1950s, and the formulation of this compound in a liposomal drug delivery system, has resulted in decades of use in systemic fungal infections. The use of liposomal amphotericin B formulation is referenced in many international guidelines for the treatment of fungal infections such as Aspergillus and cryptococcal disease and Candida infections, as well as other less common infections such as visceral leishmaniasis. With the development of liposomal amphotericin B, an improved therapeutic index could be achieved that allowed the attainment of higher drug concentrations in both the plasma and tissue while simultaneously lowering the toxicity compared with amphotericin B deoxycholate. In over 30 years of experience with this drug, a vast amount of information has been collected on preclinical and clinical efficacy against a wide variety of pathogens, as well as evidence on its toxicity. This article explores the history and nature of the liposomal formulation, the key clinical studies that developed the pharmacokinetic, safety and efficacy profile of the liposomal formulation, and the available microbiological data.

Etest ECVs/ECOFFs for Detection of Resistance in Prevalent and Three Nonprevalent Candida spp. to Triazoles and Amphotericin B and Aspergillus spp. to Caspofungin: Further Assessment of Modal Variability.

Susceptibility testing is an important tool in the clinical setting; its utility is based on the availability of categorical endpoints, breakpoints (BPs), or epidemiological cutoff values (ECVs/ECOFFs). CLSI and EUCAST have developed antifungal susceptibility testing, BPs, and ECVs for some fungal species. Although the concentration gradient strip bioMérieux Etest is useful for routine testing in the clinical laboratory, ECVs are not available for all agent/species; the lack of clinical data precludes development of BPs. We reevaluated and consolidated Etest data points from three previous studies and included new data. We defined ECOFFinder Etest ECVs for three sets of species-agent combinations: fluconazole, posaconazole, and voriconazole and 9 Candida spp.; amphotericin B and 3 nonprevalent Candida spp.; and caspofungin and 4 Aspergillus spp. The total of Etest MICs from 23 laboratories (Europe, the Americas, and South Africa) included (antifungal agent dependent): 17,242 Candida albicans, 244 C. dubliniensis, 5,129 C. glabrata species complex (SC), 275 C. guilliermondii (Meyerozyma guilliermondii), 1,133 C. krusei (Pichia kudriavzevii), 933 C. kefyr (Kluyveromyces marxianus), 519 C. lusitaniae (Clavispora lusitaniae), 2,947 C. parapsilosis SC, 2,214 C. tropicalis, 3,212 Aspergillus fumigatus, 232 A. flavus, 181 A. niger, and 267 A. terreus SC isolates. Triazole MICs for 66 confirmed non-wild-type (non-WT) Candida isolates were available (ERG11 point mutations). Distributions fulfilling CLSI ECV criteria were pooled, and ECOFFinder Etest ECVs were established for triazoles (9 Candida spp.), amphotericin B (3 less-prevalent Candida spp.), and caspofungin (4 Aspergillus spp.). Etest fluconazole ECVs could be good detectors of Candida non-WT isolates (59/61 non-WT, 4 of 6 species).

Aspergillus fumigatus and aspergillosis: From basics to clinics.

The airborne fungus Aspergillus fumigatus poses a serious health threat to humans by causing numerous invasive infections and a notable mortality in humans, especially in immunocompromised patients. Mould-active azoles are the frontline therapeutics employed to treat aspergillosis. The global emergence of azole-resistant A. fumigatus isolates in clinic and environment, however, notoriously limits the therapeutic options of mould-active antifungals and potentially can be attributed to a mortality rate reaching up to 100 %. Although specific mutations in CYP 51A are the main cause of azole resistance, there is a new wave of azole-resistant isolates with wild-type CYP 51A genotype challenging the efficacy of the current diagnostic tools. Therefore, applications of whole-genome sequencing are increasingly gaining popularity to overcome such challenges. Prominent echinocandin tolerance, as well as liver and kidney toxicity posed by amphotericin B, necessitate a continuous quest for novel antifungal drugs to combat emerging azole-resistant A. fumigatus isolates. Animal models and the tools used for genetic engineering require further refinement to facilitate a better understanding about the resistance mechanisms, virulence, and immune reactions orchestrated against A. fumigatus. This review paper comprehensively discusses the current clinical challenges caused by A. fumigatus and provides insights on how to address them.

Comparison of novel approaches for expedited pathogen identification and antimicrobial susceptibility testing against routine blood culture diagnostics.

Blood stream infections pose a major challenge for clinicians as the immediate application of an appropriate antibiotic treatment is the vital factor to safe the patients' lives. This preliminary study compares three different systems promising fast pathogen identification and susceptibility testing in comparison to conventional blood culture (BC): (i) the rapid antimicrobial susceptibility testing protocol according to EUCAST in combination with the Sepsityper® kit (sRAST), (ii) the direct inoculation method on the VITEK® 2 system (dVIT) and (iii) testing with the Accelerate Pheno® system (AccPh). All methods were assessed in terms of accuracy, time to result and usability. Twenty-three BC samples obtained from patients suffering from proven sepsis were analysed in detail. Pathogen identification was successful in 95·6, 91·3 and 91·3% in sRAST, dVIT and AccPh, respectively. Categorical agreement in antimicrobial susceptibility testing was 89·5, 96 and 96·6%, respectively. Time to result from sample entry to reporting ranged from an average of 4·6 h for sRAST and 6·9 h for AccPh to 10·6 h for dVIT. These results imply a significant shortening of reporting times at considerably high agreement rates for these new diagnostic approaches.

Polymorphisms within the ARNT2 and CX3CR1 Genes Are Associated with the Risk of Developing Invasive Aspergillosis.

Invasive aspergillosis (IA) is a life-threatening infection that affects an increasing number of patients undergoing chemotherapy or allo-transplantation, and recent studies have shown that genetic factors contribute to disease susceptibility. In this two-stage, population-based, case-control study, we evaluated whether 7 potentially functional single nucleotide polymorphisms (SNPs) within the ARNT2 and CX3CR1 genes influence the risk of IA in high-risk hematological patients. We genotyped selected SNPs in a cohort of 500 hematological patients (103 of those had been diagnosed with proven or probable IA), and we evaluated their association with the risk of developing IA. The association of the most interesting markers of IA risk was then validated in a replication population, including 474 subjects (94 IA and 380 non-IA patients). Functional experiments were also performed to confirm the biological relevance of the most interesting markers. The meta-analysis of both populations showed that carriers of the ARNT2rs1374213G, CX3CR1rs7631529A, and CX3CR1rs9823718G alleles (where the RefSeq identifier appears as a subscript) had a significantly increased risk of developing IA according to a log-additive model (P value from the meta-analysis [PMeta] = 9.8 · 10-5, PMeta = 1.5 · 10-4, and PMeta =7.9 · 10-5, respectively). Haplotype analysis also confirmed the association of the CX3CR1 haplotype with AG CGG with an increased risk of IA (P = 4.0 · 10-4). Mechanistically, we observed that monocyte-derived macrophages (MDM) from subjects carrying the ARNTR2rs1374213G allele or the GG genotype showed a significantly impaired fungicidal activity but that MDM from carriers of the ARNT2rs1374213G and CX3CR1rs9823718G or CX3CR1rs7631529A alleles had deregulated immune responses to Aspergillus conidia. These results, together with those from expression quantitative trait locus (eQTL) data browsers showing a strong correlation of the CX3CR1rs9823718G allele with lower levels of CX3CR1 mRNA in whole peripheral blood (P = 2.46 · 10-7) and primary monocytes (P = 4.31 · 10-7), highlight the role of the ARNT2 and CX3CR1 loci in modulating and predicting IA risk and provide new insights into the host immune mechanisms involved in IA development.

Candida in the Respiratory Tract Potentially Triggers Galactomannan Positivity in Nonhematological Patients.

BAL fluid samples from critically ill patients shared a rate of 29% false-positive galactomannan results. We aimed to determine whether Candida species abundance in BAL fluid causes galactomannan (GM) positivity. A total of 89 Candida culture-positive BAL fluid samples from patients without suspicion of invasive aspergillosis (IA) were analyzed. GM results were correlated with Candida species abundance, Candida species quantity, and patient data. Candida species quantities of ≥104/ml and Candida glabrata abundance were significantly associated with positive GM results. The added diagnostic value of GM in BAL fluid for diagnosing IA in critically ill patients is limited.

Method-Dependent Epidemiological Cutoff Values for Detection of Triazole Resistance in Candida and Aspergillus Species for the Sensititre YeastOne Colorimetric Broth and Etest Agar Diffusion Methods.

Although the Sensititre Yeast-One (SYO) and Etest methods are widely utilized, interpretive criteria are not available for triazole susceptibility testing of Candida or Aspergillus species. We collected fluconazole, itraconazole, posaconazole, and voriconazole SYO and Etest MICs from 39 laboratories representing all continents for (method/agent-dependent) 11,171 Candida albicans, 215 C. dubliniensis, 4,418 C. glabrata species complex, 157 C.guilliermondii (Meyerozyma guilliermondii), 676 C. krusei (Pichia kudriavzevii), 298 C.lusitaniae (Clavispora lusitaniae), 911 C.parapsilosissensu stricto, 3,691 C.parapsilosis species complex, 36 C.metapsilosis, 110 C.orthopsilosis, 1,854 C.tropicalis, 244 Saccharomyces cerevisiae, 1,409 Aspergillus fumigatus, 389 A.flavus, 130 A.nidulans, 233 A.niger, and 302 A.terreus complex isolates. SYO/Etest MICs for 282 confirmed non-wild-type (non-WT) isolates were included: ERG11 (C. albicans), ERG11 and MRR1 (C. parapsilosis), cyp51A (A. fumigatus), and CDR2 and CDR1 overexpression (C. albicans and C. glabrata, respectively). Interlaboratory modal agreement was superior by SYO for yeast species and by the Etest for Aspergillus spp. Distributions fulfilling CLSI criteria for epidemiological cutoff value (ECV) definition were pooled, and we proposed SYO ECVs for S. cerevisiae and 9 yeast and 3 Aspergillus species and Etest ECVs for 5 yeast and 4 Aspergillus species. The posaconazole SYO ECV of 0.06 µg/ml for C. albicans and the Etest itraconazole ECV of 2 µg/ml for A. fumigatus were the best predictors of non-WT isolates. These findings support the need for method-dependent ECVs, as, overall, the SYO appears to perform better for susceptibility testing of yeast species and the Etest appears to perform better for susceptibility testing of Aspergillus spp. Further evaluations should be conducted with more Candida mutants.

Posaconazole MIC Distributions for Aspergillus fumigatus Species Complex by Four Methods: Impact of cyp51A Mutations on Estimation of Epidemiological Cutoff Values.

Estimating epidemiological cutoff endpoints (ECVs/ECOFFS) may be hindered by the overlap of MICs for mutant and nonmutant strains (strains harboring or not harboring mutations, respectively). Posaconazole MIC distributions for the Aspergillus fumigatus species complex were collected from 26 laboratories (in Australia, Canada, Europe, India, South and North America, and Taiwan) and published studies. Distributions that fulfilled CLSI criteria were pooled and ECVs were estimated. The sensitivity of three ECV analytical techniques (the ECOFFinder, normalized resistance interpretation [NRI], derivatization methods) to the inclusion of MICs for mutants was examined for three susceptibility testing methods (the CLSI, EUCAST, and Etest methods). The totals of posaconazole MICs for nonmutant isolates (isolates with no known cyp51A mutations) and mutant A. fumigatus isolates were as follows: by the CLSI method, 2,223 and 274, respectively; by the EUCAST method, 556 and 52, respectively; and by Etest, 1,365 and 29, respectively. MICs for 381 isolates with unknown mutational status were also evaluated with the Sensititre YeastOne system (SYO). We observed an overlap in posaconazole MICs among nonmutants and cyp51A mutants. At the commonly chosen percentage of the modeled wild-type population (97.5%), almost all ECVs remained the same when the MICs for nonmutant and mutant distributions were merged: ECOFFinder ECVs, 0.5 µg/ml for the CLSI method and 0.25 µg/ml for the EUCAST method and Etest; NRI ECVs, 0.5 µg/ml for all three methods. However, the ECOFFinder ECV for 95% of the nonmutant population by the CLSI method was 0.25 µg/ml. The tentative ECOFFinder ECV with SYO was 0.06 µg/ml (data from 3/8 laboratories). Derivatization ECVs with or without mutant inclusion were either 0.25 µg/ml (CLSI, EUCAST, Etest) or 0.06 µg/ml (SYO). It appears that ECV analytical techniques may not be vulnerable to overlap between presumptive wild-type isolates and cyp51A mutants when up to 11.6% of the estimated wild-type population includes mutants.

Multicenter Study of Method-Dependent Epidemiological Cutoff Values for Detection of Resistance in Candida spp. and Aspergillus spp. to Amphotericin B and Echinocandins for the Etest Agar Diffusion Method.

Method-dependent Etest epidemiological cutoff values (ECVs) are not available for susceptibility testing of either Candida or Aspergillus species with amphotericin B or echinocandins. In addition, reference caspofungin MICs for Candida spp. are unreliable. Candida and Aspergillus species wild-type (WT) Etest MIC distributions (microorganisms in a species-drug combination with no detectable phenotypic resistance) were established for 4,341 Candida albicans, 113 C. dubliniensis, 1,683 C. glabrata species complex (SC), 709 C. krusei, 767 C. parapsilosis SC, 796 C. tropicalis, 1,637 Aspergillus fumigatus SC, 238 A. flavus SC, 321 A. niger SC, and 247 A. terreus SC isolates. Etest MICs from 15 laboratories (in Argentina, Europe, Mexico, South Africa, and the United States) were pooled to establish Etest ECVs. Anidulafungin, caspofungin, micafungin, and amphotericin B ECVs (in micrograms per milliliter) encompassing ≥97.5% of the statistically modeled population were 0.016, 0.5, 0.03, and 1 for C. albicans; 0.03, 1, 0.03, and 2 for C. glabrata SC; 0.06, 1, 0.25, and 4 for C. krusei; 8, 4, 2, and 2 for C. parapsilosis SC; and 0.03, 1, 0.12, and 2 for C. tropicalis The amphotericin B ECV was 0.25 µg/ml for C. dubliniensis and 2, 8, 2, and 16 µg/ml for the complexes of A. fumigatus, A. flavus, A. niger, and A. terreus, respectively. While anidulafungin Etest ECVs classified 92% of the Candida fks mutants evaluated as non-WT, the performance was lower for caspofungin (75%) and micafungin (84%) cutoffs. Finally, although anidulafungin (as an echinocandin surrogate susceptibility marker) and amphotericin B ECVs should identify Candida and Aspergillus isolates with reduced susceptibility to these agents using the Etest, these ECVs will not categorize a fungal isolate as susceptible or resistant, as breakpoints do.

Mammary candidiasis: molecular-based detection of Candida species in human milk samples.

In this prospective and monocentric study, we investigated the performance of a commercialized real-time polymerase chain reaction (RT-PCR) test system for the specific detection of DNA from Candida albicans, C. dubliniensis, C. glabrata, C. krusei, C. lusitaniae, C. parapsilosis, and C. tropicalis in human milk samples of patients suspicious of mammary candidiasis. For this purpose, 43 breast-feeding women with characteristic symptoms of mammary candidiasis and 40 asymptomatic controls were enrolled. By culture, Candida spp. were detected in 8.8 % (4/46) and 9.3 % (4/43) of patient and control samples, respectively. Candida albicans (2/46), C. parapsilosis (1/46), and C. guilliermondii (1/46) were present in patient samples, and C. lusitaniae (3/43) and C. guilliermondii (1/43) were present in the controls. After RT-PCR was applied, Candida spp. were found to be present in 67.4 % (31/46) and 79.1 % (34/43) of patient and control samples investigated, respectively. PCR detection of C. albicans and C. parapsilosis revealed only a low sensitivity and specificity of 67.4 % and 41.9 %, respectively. Our data do not support the use of Candida RT-PCR for sensitive and specific diagnosis of mammary candidiasis.

Polymorphisms in Host Immunity-Modulating Genes and Risk of Invasive Aspergillosis: Results from the AspBIOmics Consortium.

Recent studies suggest that immune-modulating single-nucleotide polymorphisms (SNPs) influence the risk of developing cancer-related infections. Here, we evaluated whether 36 SNPs within 14 immune-related genes are associated with the risk of invasive aspergillosis (IA) and whether genotyping of these variants might improve disease risk prediction. We conducted a case-control association study of 781 immunocompromised patients, 149 of whom were diagnosed with IA. Association analysis showed that the IL4Rrs2107356 and IL8rs2227307 SNPs (using dbSNP numbering) were associated with an increased risk of IA (IL4Rrs2107356 odds ratio [OR], 1.92; 95% confidence interval [CI], 1.20 to 3.09; IL8rs2227307 OR, 1.73; 95% CI, 1.06 to 2.81), whereas the IL12Brs3212227 and IFNγrs2069705 variants were significantly associated with a decreased risk of developing the infection (IL12Brs3212227 OR, 0.60; 95% CI, 0.38 to 0.96; IFNγrs2069705 OR, 0.63; 95% CI, 0.41 to 0.97). An allogeneic hematopoietic stem cell transplantation (allo-HSCT)-stratified analysis revealed that the effect observed for the IL4Rrs2107356 and IFNγrs2069705 SNPs was stronger in allo-HSCT (IL4Rrs2107356 OR, 5.63; 95% CI, 1.20 to 3.09; IFNγrs2069705 OR, 0.24; 95% CI, 0.10 to 0.59) than in non-HSCT patients, suggesting that the presence of these SNPs renders patients more vulnerable to infection, especially under severe and prolonged immunosuppressive conditions. Importantly, in vitro studies revealed that carriers of the IFNγrs2069705C allele showed a significantly increased macrophage-mediated neutralization of fungal conidia (P = 0.0003) and, under stimulation conditions, produced higher levels of gamma interferon (IFNγ) mRNA (P = 0.049) and IFNγ and tumor necrosis factor alpha (TNF-α) cytokines (P value for 96 h of treatment with lipopolysaccharide [PLPS-96 h], 0.057; P value for 96 h of treatment with phytohemagglutinin [PPHA-96 h], 0.036; PLPS+PHA-96 h = 0.030; PPHA-72 h = 0.045; PLPS+PHA-72 h = 0.018; PLPS-96 h = 0.058; PLPS+PHA-96 h = 0.0058). Finally, we also observed that the addition of SNPs significantly associated with IA to a model including clinical variables led to a substantial improvement in the discriminatory ability to predict disease (area under the concentration-time curve [AUC] of 0.659 versus AUC of 0.564; P-2 log likehood ratio test = 5.2 · 10(-4) and P50.000 permutation test = 9.34 · 10(-5)). These findings suggest that the IFNγrs2069705 SNP influences the risk of IA and that predictive models built with IFNγ, IL8, IL12p70, and VEGFA variants can used to predict disease risk and to implement risk-adapted prophylaxis or diagnostic strategies.

Prospective multicenter international surveillance of azole resistance in Aspergillus fumigatus.

To investigate azole resistance in clinical Aspergillus isolates, we conducted prospective multicenter international surveillance. A total of 3,788 Aspergillus isolates were screened in 22 centers from 19 countries. Azole-resistant A. fumigatus was more frequently found (3.2% prevalence) than previously acknowledged, causing resistant invasive and noninvasive aspergillosis and severely compromising clinical use of azoles.

Evaluation of a modified EUCAST fragmented-mycelium inoculum method for in vitro susceptibility testing of dermatophytes and the activity of novel antifungal agents.

For antifungal susceptibility testing of nonsporulating or poorly sporulating dermatophytes, a fragmented-mycelium inoculum preparation method was established and compared to broth microdilution testing according to CLSI and EUCAST guidelines. Moreover, the in vitro activity of new antifungal agents against dermatophytes was evaluated. Agreement between the mycelial inoculum method and the CLSI broth microdilution method was high (93% to 100%). Echinocandins (minimal effective concentration [MEC], ≤0.5 mg/liter) and posaconazole (MIC, ≤3.00 mg/liter) showed good activity against all tested dermatophytes.

Multicenter evaluation of MIC distributions for epidemiologic cutoff value definition to detect amphotericin B, posaconazole, and itraconazole resistance among the most clinically relevant species of Mucorales.

Clinical breakpoints (CBPs) have not been established for the Mucorales and any antifungal agent. In lieu of CBPs, epidemiologic cutoff values (ECVs) are proposed for amphotericin B, posaconazole, and itraconazole and four Mucorales species. Wild-type (WT) MIC distributions (organisms in a species-drug combination with no detectable acquired resistance mechanisms) were defined with available pooled CLSI MICs from 14 laboratories (Argentina, Australia, Canada, Europe, India, Mexico, and the United States) as follows: 10 Apophysomyces variabilis, 32 Cunninghamella bertholletiae, 136 Lichtheimia corymbifera, 10 Mucor indicus, 123 M. circinelloides, 19 M. ramosissimus, 349 Rhizopus arrhizus, 146 R. microsporus, 33 Rhizomucor pusillus, and 36 Syncephalastrum racemosum isolates. CLSI broth microdilution MICs were aggregated for the analyses. ECVs comprising ≥95% and ≥97.5% of the modeled populations were as follows: amphotericin B ECVs for L. corymbifera were 1 and 2 µg/ml, those for M. circinelloides were 1 and 2 µg/ml, those for R. arrhizus were 2 and 4 µg/ml, and those for R. microsporus were 2 and 2 µg/ml, respectively; posaconazole ECVs for L. corymbifera were 1 and 2, those for M. circinelloides were 4 and 4, those for R. arrhizus were 1 and 2, and those for R. microsporus were 1 and 2, respectively; both itraconazole ECVs for R. arrhizus were 2 µg/ml. ECVs may aid in detecting emerging resistance or isolates with reduced susceptibility (non-WT MICs) to the agents evaluated.

Phylogenetic relationships matter: antifungal susceptibility among clinically relevant yeasts.

The objective of this study was 2-fold: to evaluate whether phylogenetically closely related yeasts share common antifungal susceptibility profiles (ASPs) and whether these ASPs can be predicted from phylogeny. To address this question, 9,627 yeast strains were collected and tested for their antifungal susceptibility. Isolates were reidentified by considering recent changes in taxonomy and nomenclature. A phylogenetic (PHYLO) code based on the results of multilocus sequence analyses (large-subunit rRNA, small-subunit rRNA, translation elongation factor 1α, RNA polymerase II subunits 1 and 2) and the classification of the cellular neutral sugar composition of coenzyme Q and 18S ribosomal DNA was created to group related yeasts into PHYLO groups. The ASPs were determined for fluconazole, itraconazole, and voriconazole in each PHYLO group. The majority (95%) of the yeast strains were Ascomycetes. After reclassification, a total of 23 genera and 54 species were identified, resulting in an increase of 64% of genera and a decrease of 5% of species compared with the initial identification. These taxa were assigned to 17 distinct PHYLO groups (Ascomycota, n=13; Basidiomycota, n=4). ASPs for azoles were similar among members of the same PHYLO group and different between the various PHYLO groups. Yeast phylogeny may be an additional tool to significantly enhance the assessment of MIC values and to predict antifungal susceptibility, thereby more rapidly initiating appropriate patient management.

Positions and numbers of FKS mutations in Candida albicans selectively influence in vitro and in vivo susceptibilities to echinocandin treatment.

Candidemia is the fourth most common kind of microbial bloodstream infection, with Candida albicans being the most common causative species. Echinocandins are employed as the first-line treatment for invasive candidiasis until the fungal species is determined and confirmed by clinical diagnosis. Echinocandins block the FKS glucan synthases responsible for embedding ß-(1,3)-d-glucan in the cell wall. The increasing use of these drugs has led to the emergence of antifungal resistance, and elevated MICs have been associated with single-residue substitutions in specific hot spot regions of FKS1 and FKS2. Here, we show for the first time the caspofungin-mediated in vivo selection of a double mutation within one allele of the FKS1 hot spot 1 in a clinical isolate. We created a set of isogenic mutants and used a hematogenous murine model to evaluate the in vivo outcomes of echinocandin treatment. Heterozygous and homozygous double mutations significantly enhance the in vivo resistance of C. albicans compared with the resistance seen with heterozygous single mutations. The various FKS1 hot spot mutations differ in the degree of their MIC increase, substance-dependent in vivo response, and impact on virulence. Our results demonstrate that echinocandin EUCAST breakpoint definitions correlate with the in vivo response when a standard dosing regimen is used but cannot predict the in vivo response after a dose escalation. Moreover, patients colonized by a C. albicans strain with multiple mutations in FKS1 have a higher risk for therapeutic failure.

Multicenter study of anidulafungin and micafungin MIC distributions and epidemiological cutoff values for eight Candida species and the CLSI M27-A3 broth microdilution method.

Since epidemiological cutoff values (ECVs) using CLSI MICs from multiple laboratories are not available for Candida spp. and the echinocandins, we established ECVs for anidulafungin and micafungin on the basis of wild-type (WT) MIC distributions (for organisms in a species-drug combination with no detectable acquired resistance mechanisms) for 8,210 Candida albicans, 3,102 C. glabrata, 3,976 C. parapsilosis, 2,042 C. tropicalis, 617 C. krusei, 258 C. lusitaniae, 234 C. guilliermondii, and 131 C. dubliniensis isolates. CLSI broth microdilution MIC data gathered from 15 different laboratories in Canada, Europe, Mexico, Peru, and the United States were aggregated to statistically define ECVs. ECVs encompassing 97.5% of the statistically modeled population for anidulafungin and micafungin were, respectively, 0.12 and 0.03 µg/ml for C. albicans, 0.12 and 0.03 µg/ml for C. glabrata, 8 and 4 µg/ml for C. parapsilosis, 0.12 and 0.06 µg/ml for C. tropicalis, 0.25 and 0.25 µg/ml for C. krusei, 1 and 0.5 µg/ml for C. lusitaniae, 8 and 2 µg/ml for C. guilliermondii, and 0.12 and 0.12 µg/ml for C. dubliniensis. Previously reported single and multicenter ECVs defined in the present study were quite similar or within 1 2-fold dilution of each other. For a collection of 230 WT isolates (no fks mutations) and 51 isolates with fks mutations, the species-specific ECVs for anidulafungin and micafungin correctly classified 47 (92.2%) and 51 (100%) of the fks mutants, respectively, as non-WT strains. These ECVs may aid in detecting non-WT isolates with reduced susceptibility to anidulafungin and micafungin due to fks mutations.

Multilaboratory study of epidemiological cutoff values for detection of resistance in eight Candida species to fluconazole, posaconazole, and voriconazole.

Although epidemiological cutoff values (ECVs) have been established for Candida spp. and the triazoles, they are based on MIC data from a single laboratory. We have established ECVs for eight Candida species and fluconazole, posaconazole, and voriconazole based on wild-type (WT) MIC distributions for isolates of C. albicans (n=11,241 isolates), C. glabrata (7,538), C. parapsilosis (6,023), C. tropicalis (3,748), C. krusei (1,073), C. lusitaniae (574), C. guilliermondii (373), and C. dubliniensis (162). The 24-h CLSI broth microdilution MICs were collated from multiple laboratories (in Canada, Brazil, Europe, Mexico, Peru, and the United States). The ECVs for distributions originating from ≥6 laboratories, which included ≥95% of the modeled WT population, for fluconazole, posaconazole, and voriconazole were, respectively, 0.5, 0.06 and 0.03 µg/ml for C. albicans, 0.5, 0.25, and 0.03 µg/ml for C. dubliniensis, 8, 1, and 0.25 µg/ml for C. glabrata, 8, 0.5, and 0.12 µg/ml for C. guilliermondii, 32, 0.5, and 0.25 µg/ml for C. krusei, 1, 0.06, and 0.06 µg/ml for C. lusitaniae, 1, 0.25, and 0.03 µg/ml for C. parapsilosis, and 1, 0.12, and 0.06 µg/ml for C. tropicalis. The low number of MICs (<100) for other less prevalent species (C. famata, C. kefyr, C. orthopsilosis, C. rugosa) precluded ECV definition, but their MIC distributions are documented. Evaluation of our ECVs for some species/agent combinations using published individual MICs for 136 isolates (harboring mutations in or upregulation of ERG11, MDR1, CDR1, or CDR2) and 64 WT isolates indicated that our ECVs may be useful in distinguishing WT from non-WT isolates.

Multicenter study of isavuconazole MIC distributions and epidemiological cutoff values for Aspergillus spp. for the CLSI M38-A2 broth microdilution method.

Epidemiological cutoff values (ECVs) were established for the new triazole isavuconazole and Aspergillus species wild-type (WT) MIC distributions (organisms in a species-drug combination with no detectable acquired resistance mechanisms) that were defined with 855 Aspergillus fumigatus, 444 A. flavus, 106 A. nidulans, 207 A. niger, 384 A. terreus, and 75 A. versicolor species complex isolates; 22 Aspergillus section Usti isolates were also included. CLSI broth microdilution MIC data gathered in Europe, India, Mexico, and the United States were aggregated to statistically define ECVs. ECVs were 1 µg/ml for the A. fumigatus species complex, 1 µg/ml for the A. flavus species complex, 0.25 µg/ml for the A. nidulans species complex, 4 µg/ml for the A. niger species complex, 1 µg/ml for the A. terreus species complex, and 1 µg/ml for the A. versicolor species complex; due to the small number of isolates, an ECV was not proposed for Aspergillus section Usti. These ECVs may aid in detecting non-WT isolates with reduced susceptibility to isavuconazole due to cyp51A (an A. fumigatus species complex resistance mechanism among the triazoles) or other mutations.

Interlaboratory variability of Caspofungin MICs for Candida spp. Using CLSI and EUCAST methods: should the clinical laboratory be testing this agent?

Although Clinical and Laboratory Standards Institute (CLSI) clinical breakpoints (CBPs) are available for interpreting echinocandin MICs for Candida spp., epidemiologic cutoff values (ECVs) based on collective MIC data from multiple laboratories have not been defined. While collating CLSI caspofungin MICs for 145 to 11,550 Candida isolates from 17 laboratories (Brazil, Canada, Europe, Mexico, Peru, and the United States), we observed an extraordinary amount of modal variability (wide ranges) among laboratories as well as truncated and bimodal MIC distributions. The species-specific modes across different laboratories ranged from 0.016 to 0.5 µg/ml for C. albicans and C. tropicalis, 0.031 to 0.5 µg/ml for C. glabrata, and 0.063 to 1 µg/ml for C. krusei. Variability was also similar among MIC distributions for C. dubliniensis and C. lusitaniae. The exceptions were C. parapsilosis and C. guilliermondii MIC distributions, where most modes were within one 2-fold dilution of each other. These findings were consistent with available data from the European Committee on Antimicrobial Susceptibility Testing (EUCAST) (403 to 2,556 MICs) for C. albicans, C. glabrata, C. krusei, and C. tropicalis. Although many factors (caspofungin powder source, stock solution solvent, powder storage time length and temperature, and MIC determination testing parameters) were examined as a potential cause of such unprecedented variability, a single specific cause was not identified. Therefore, it seems highly likely that the use of the CLSI species-specific caspofungin CBPs could lead to reporting an excessive number of wild-type (WT) isolates (e.g., C. glabrata and C. krusei) as either non-WT or resistant isolates. Until this problem is resolved, routine testing or reporting of CLSI caspofungin MICs for Candida is not recommended; micafungin or anidulafungin data could be used instead.