EUCAST Method Research Articles

Single-Center Evaluation of an Agar-Based Screening for Azole Resistance in Aspergillus fumigatus by Using VIPcheck.

Antifungal susceptibility testing is an essential tool for guiding therapy, although EUCAST and CLSI reference methods are often available only in specialized centers. We studied the performance of an agar-based screening method for the detection of azole resistance in Aspergillus fumigatus cultures. The VIPcheck consists of four wells containing voriconazole, itraconazole, posaconazole, or a growth control. Ninety-six A. fumigatus isolates were used. Thirty-three isolates harbored a known resistance mechanism: TR34/L98H (11 isolates), TR46/Y121F/T289A (6 isolates), TR53 (2 isolates), and 14 isolates with other cyp51A gene point mutations. Eighteen resistant isolates had no cyp51A-mediated azole resistance. Forty-five isolates had a wild-type (WT) azole phenotype. Four technicians and two inexperienced interns, blinded to the genotype/phenotype, read the plates visually after 24 h and 48 h and documented minimal growth, uninhibited growth, and no growth. The performance was compared to the EUCAST method. After 24 h of incubation, the mean sensitivity and specificity were 0.54 and 1.00, respectively, with uninhibited growth as the threshold. After 48 h of incubation, the performance mean sensitivity and specificity were 0.98 and 0.93, respectively, with minimal growth. The performance was not affected by observer experience in mycology. The interclass correlation coefficient was 0.87 after 24 h and 0.85 after 48 h. VIPcheck enabled the selection of azole-resistant A. fumigatus colonies, with a mean sensitivity and specificity of 0.98 and 0.93, respectively. Uninhibited growth on any azole-containing well after 24 h and minimal growth after 48 h were indicative of resistance. These results indicate that the VIPcheck is an easy-to-use tool for azole resistance screening and the selection of colonies that require MIC testing.

Azole-resistant Aspergillus fumigatus in sawmills of Eastern France.

Emergence of azole-resistant Aspergillus fumigatus complicates management of Aspergillus diseases. Currently, selection pressure caused by azole fungicide use in farming is strongly suspected of creating resistance. As sawmills also use azole fungicides, we investigated the presence of azole-resistant strains in this environment and studied the relationship between azole fungicide use and development of resistance. Air (n=200) and substrate (n=600) samples were taken in 20 sawmills. Azole-resistant strains (Etest and EUCAST methods) were confirmed by sequencing the cyp51A gene and its promoters. Dosage of propiconazole and tebuconazole was performed by gas chromatography coupled with mass spectrometry. Twenty-four azole-resistant A. fumigatus strains were collected among 20 of the 600 substrate samples (3%). Eighty-three percent of theses strains had TR34 /L98H mutation. A significantly higher number of resistant strains was collected in sawmills using fungicide products made with propiconazole mixed with a high concentration of tebuconazole (P=0·009). The presence of resistant strains was significantly linked to propiconazole quantities in substrates (P=0·03). The outcome of azole-resistant A. fumigatus carrying TR34 /L98H mutation seems to greatly depend on the azole fungicide formulation and quantities of azole. These preliminary results are valuable to propose new approaches limiting the emergence of azole-resistant strains. Azole resistance is an emerging problem in A. fumigatus and threatens clinical advances made possible by the use of azole antifungals in the treatment of Aspergillus-related diseases. Azole fungicides are also used in the wood industry, notably in sawmills, to protect wood from wood-destroying fungi. Through our study, we show that sawmills represent another professional environment affected by the presence of azole-resistant A. fumigatus strains carrying the TR34 /L98H mutation. Moreover, this study provides valuable preliminary results to propose some new approaches to limit the emergence of azole-resistant A. fumigatus strains.

Comparative Evaluation of Etest, EUCAST, and CLSI Methods for Amphotericin B, Voriconazole, and Posaconazole against Clinically Relevant Fusarium Species.

We compared EUCAST and CLSI methods versus Etest for antifungal susceptibility testing of 20 clinically relevant Fusarium species against amphotericin B, posaconazole, and voriconazole. The median Etest amphotericin B and posaconazole MICs were 1 dilution higher than the median EUCAST and the CLSI MICs. The essential agreement (within ±1/±2 dilutions) was 60/90%, 80/95%, and 70/85% between the Etest and EUCAST methods and 80/95%, 75/95%, and 45/100% between the Etest and CLSI methods for amphotericin B, voriconazole, and posaconazole, respectively. The categorical agreement was >85%. Etest can be used for antifungal susceptibility testing of Fusarium species.

Fungemia due to rare opportunistic yeasts: data from a population-based surveillance in Spain.

Fungemia due to rare yeasts constitutes an emerging but poorly investigated condition. Data on risk factors, clinical features, therapy, and outcome of episodes of fungemia due to rare (non-Candida, non-Cryptococcus) yeasts were analyzed in a population-based surveillance program conducted in 29 Spanish hospitals between May 2010 and April 2011. Species identification (DNA sequencing) and antifungal susceptibility testing (EUCAST and CLSI methods) were centrally performed. Fourteen out of 767 episodes of fungemia (1.8%) were due to rare yeasts: Trichosporon asahii, Magnusiomyces capitatus (three cases each), Rhodotorula mucilaginosa, Wickerhamomyces anomalus (two cases each), and Pichia kudriavzevii, Cyberlindnera fabianii, Kodamaea ohmeri, and Lodderomyces elongisporus (one case each). Misidentification by local laboratories was observed in two isolates. Breakthrough fungemia occurred in two episodes due to M. capitatus MIC values for echinocandins were generally high (particularly for M. capitatus, T. asahii, and R. mucilaginosa isolates [≥2mg/l]), whereas T. asahii isolates showed MICs ≥1mg/l to amphotericin B. Patients with fungemia due to rare yeasts were more likely to have hematological malignancies (28.6%vs. 7.8%; P-value = .021), chronic lung disease (50.0%vs. 22.3%; P-value = .023), and prior immunosuppression (57.1%vs. 22.2%; P-value = .005) compared to those with candidemia. The rate of clinical failure (persistent fungemia and/or 30-day mortality) was 46.2% and did not significantly differ from that observed in episodes of candidemia. In conclusion, non-Candida, non-Cryptococcus yeasts are uncommon causes of fungemia, with immunosuppression and chronic lung disease as predisposing factors. Outcome does not appear to be worse than that of candidemia.

Intra- and Interlaboratory Agreement in Assessing the In Vitro Activity of Micafungin against Common and Rare Candida Species with the EUCAST, CLSI, and Etest Methods

The emergence of resistant strains among common and rare Candida species necessitates continuous monitoring of the in vitro susceptibilities of those isolates. We therefore assessed the in vitro activities of micafungin against 1,099 molecularly identified isolates belonging to 5 common and 20 rare Candida species by the EUCAST, CLSI, and Etest methods, assessing both the intralaboratory agreement and the interlaboratory agreement for two centers. The median micafungin EUCAST MICs were as follows, from the lowest to the highest: for Candida albicans, 0.004 mg/liter; for C. glabrata, 0.016 mg/liter; for C. tropicalis, 0.031 mg/liter; for C. krusei, 0.125 mg/liter; for C. parapsilosis, 2 mg/liter. Among rare Candida species, high MICs were found for C. guilliermondii, C. lipolytica, C. orthopsilosis, C. metapsilosis, and C. fermentati. No resistant isolates were found by the CLSI method, whereas resistance rates of 1 to 2% were found by the EUCAST method. Overall, the EUCAST method resulted in MICs 1 to 2 dilutions higher than those found by the CLSI and Etest methods. The intra- and interlaboratory agreement between methods was >92%, except for the interlaboratory agreement between the EUCAST and CLSI methods (81%), where 17 to 31% of the differences were >2 2-fold dilutions for C. albicans, C. glabrata, C. tropicalis, and other rare Candida species and <6% for C. parapsilosis and C. krusei For the other interlaboratory comparisons, the EUCAST method resulted in higher MICs than the Etest method for all species, but <7% of these differences were >2 2-fold dilutions. Overall, the CLSI method resulted in lower MICs than the Etest method, with 11% of all isolates demonstrating >2 2-fold-dilution differences (6 to 20% for C. albicans, C. tropicalis, and rare Candida species; <5% for C. glabrata, C. krusei, and C. parapsilosis) and smaller differences found after 24 h. Despite these differences, categorical agreement was excellent (>97%), with only 1 to 2% very major errors between the EUCAST method and the other two methods.

Triazole resistance in Aspergillus fumigatus isolates from patients with cystic fibrosis in Italy

BackgroundAspergillus fumigatus is frequently recovered from respiratory secretions of cystic fibrosis (CF) patients. Azole resistance has been increasingly reported. ObjectivesTo assess the prevalence of azole resistance in A. fumigatus isolates from patients followed by two CF centers of northern Italy. Methods423 isolates (220 patients) were screened for azole resistance. Resistance was confirmed with the EUCAST method and cyp51A gene sequencing. Microsatellite genotyping was performed and results were compared with those of environmental resistant isolates. ResultsNo resistance was detected in one center, while 8.2% of the patients of the other center harbored resistant isolates. The TR34/L98H alteration in the cyp51A gene, present in seven cases, resulted associated with poor in-vitro activity of all tested azoles. ConclusionsThe environmental origin of the resistance seems to be probable since azole resistance was found also in naïve patients and an identical microsatellite genotype in clinical and environmental isolates was observed.

Multicenter Comparison of the Etest and EUCAST Methods for Antifungal Susceptibility Testing of Candida Isolates to Micafungin.

In vitro susceptibility of 933 Candida isolates, from 16 French hospitals, to micafungin was determined using the Etest in each center. All isolates were then sent to a single center for determination of MICs by the EUCAST reference method. Overall essential agreement between the two tests was 98.5% at ±2 log2 dilutions and 90.2% at ±1 log2 dilutions. Categorical agreement was 98.2%. The Etest is a valuable alternative to EUCAST for the routine determination of micafungin MICs in medical mycology laboratories.

Striking differences in predisposing factors and outcome of uncommon yeast species-related fungaemia based on a cohort study (2002–2014)

Background Comparison between uncommon yeast species (UYS)- and Candida albicans-related fungaemia can uncover specific predisposing factors with potential impact on treatment strategies. Methods Clinical data (including follow-up) and isolates responsible for fungaemia were collected prospectively from 27 hospitals (Paris, France ; 01/10/2002-31/12/2014). Univariate and multivariate analyses were performed to compare UYS with C. albicans fungaemia. Findings We analysed 339 episodes of UYS fungaemia. Of the 35 different UYS (27 ascomycetes, 8 basidiomycetes), 11 had caspofungin MIC50 > = 0.5 mg/L (CAS-R), and 15 had fluconazole MIC50 > = 8 mg/L (FCZ-R, EUCAST method). The incidence of UYS fungaemia was stable over time. When comparing with 1997 single episodes of C. albicans fungaemia, haematological malignancies (OR = 2.42[1.82–3.22]) and prior exposure to antifungal drugs (OR = 1.86[1.29–2.67]) were independent predisposing factors for UYS upon multivariate analysis. However, when considering the species/genera level, only infections due to species related to C. kefyr (OR = 3.95[2.40–6.53]) and to Trichosporon spp. (OR = 5.42[1.73–16.96]) remained associated with haematological malignancies, those due to Geotrichum spp. with acute leukaemia (OR = 52.61[17.64–156.88]), and the later two with prior exposure to caspofungin (OR = 15.6[3.6–67.4] and OR = 12.0[3.2–45.3], respectively) but not to fluconazole. The global mortality at day 30 of the CAS-R and FCZ-R species was not different compared with C. albicans, (40%, 40%, and 35% respectively), but very divergent results were observed according to the species. Interpretation UYS encompass a huge diversity of species, each with its own behaviour and predisposing factors. This underlines the need for rapid identification of isolate at the species level in order to optimize antifungal treatment.

Comparison of the EUCAST and CLSI Broth Microdilution Methods for Testing Isavuconazole, Posaconazole, and Amphotericin B against Molecularly Identified Mucorales Species.

We compared EUCAST and CLSI antifungal susceptibility testing (AFST) methods for triazoles and amphotericin B against 124 clinical Mucorales isolates. The EUCAST method yielded MIC values 1- to 3-fold dilutions higher than those of the CLSI method for amphotericin B. The essential agreements between the two methods for triazoles were high, i.e., 99.1% (voriconazole), 98.3% (isavuconazole), and 87% (posaconazole), whereas it was significantly lower for amphotericin B (66.1%). Strategies for harmonization of the two methods for Mucorales AFST are warranted.

Antimicrobial susceptibility testing breakpoints and methods from BSAC to EUCAST.

The BSAC Standing Committee on Antimicrobial Susceptibility Testing is one of several European national breakpoint committees that agreed in 2002 to harmonize clinical MIC breakpoints. The process of harmonization has since been completed for commonly used agents, and breakpoints for new agents have been set by EUCAST in accordance with a procedure defined by the EMA. EUCAST breakpoints have now been adopted by a large majority of laboratories in Europe. BSAC implemented the EUCAST breakpoints in its own disc diffusion susceptibility testing method as harmonized breakpoints were agreed to over the years. Since the development of the EUCAST disc diffusion method, several countries with their own disc diffusion methods have switched to the EUCAST method, and BSAC will replace support of its own disc diffusion method with support for the EUCAST method from January 2016. The EUCAST breakpoints are also available in automated systems. The harmonized breakpoints and methods will help to avoid different reports of susceptibility for the same isolate in different countries and enable more reliable comparison of resistance rates in surveillance studies in different countries.

Prospective evaluation of azole resistance in Aspergillus fumigatus clinical isolates in France.

Several studies, especially in Europe, have recently reported the emerging phenomenon of azole resistance in Aspergillus fumigatus, but very few data are available in France. Our study aimed to determine the resistance prevalence in A. fumigatus isolates recovered from clinical samples over a 1-year period in two university hospital centers. All A. fumigatus isolates were screened for azole resistance using RPMI agar plates supplemented with itraconazole and voriconazole. Resistance was then confirmed by the EUCAST method. A part of the beta-tubulin gene was amplified for resistant isolates to confirm the A. fumigatus species, and the Cyp51A gene and its promoter were afterward sequenced to detect mutations potentially responsible for this resistance. One hundred sixty-five A. fumigatus isolates were recovered from 134 patients. Three isolates recovered from three patients were found resistant with MICs of >8 mg/l, 4 mg/l, and 1 mg/l for itraconazole, voriconazole, and posaconazole, respectively. The TR34/L98H mutation, previously and largely described in other countries, was detected in the three isolates. Our study demonstrated the occurrence of azole resistance among unselected A. fumigatus clinical isolates, with an overall prevalence of 1.8%.

Determination of the minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) of selected antimicrobials in bovine and swine Pasteurella multocida, Escherichia coli, and Staphylococcus aureus isolates

We compared the values of the minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) values ​​of three antimicrobial agents for 72 bovine isolates ofPasteurella multocida, 80 swine isolates ofP. multocida, 80 bovine isolates ofEscherichia coli, 80 swine isolates ofE. coli, and 80 isolates ofStaphylococcus aureusfrom bovine mastitis. The ratio of MIC90​​/MPC90which limited mutant selection window (MSW) was ≤ 0.12/4 mg/l for enrofloxacin, 0.5/≥ 64 mg/l for florfenicol and 4/≥ 128 mg/l for tulathromycin in bovineP. multocidaisolates, ≤ 0.12/2 mg/l for enrofloxacin, 0.5/≥ 64 mg/l for florfenicol and 4/≥ 128 mg/l for tulathromycin in swineP. multocidaisolates, 1/16 mg/l for enrofloxacin, 8/≥ 64 mg/l for florfenicol and 8/≥ 128 mg/l for tulathromycin in bovineE. coliisolates, 0.5/16 mg/l for enrofloxacin, ≥ 64/≥ 64 mg/l for florfenicol and 8/≥ 128 mg/l for tulathromycin in swineE. coliisolates, and 0.25/16 mg/l for enrofloxacin, 4/≥ 64 mg/l for florfenicol and 4/≥ 128 mg/l for tulathromycin inS. aureusisolates. These findings indicate that the dosage of antimicrobial agents to achieve serum concentration equal to or higher than MPC could reduce selection of resistant bacterial subpopulation.

Susceptibility breakpoints and target values for therapeutic drug monitoring of voriconazole and Aspergillus fumigatus in an in vitro pharmacokinetic/pharmacodynamic model

Although voriconazole reached the bedside 10 years ago and became the standard care in the treatment of invasive aspergillosis, reliable clinical breakpoints are still in high demand. Moreover, this has increased due to the recent emergence of azole resistance. Four clinical wild-type and non-wild-type A. fumigatus isolates with voriconazole CLSI MICs in the range of 0.125-2 mg/L were tested in an in vitro pharmacokinetic (PK)/pharmacodynamic (PD) model. Mouse PK was simulated and in vitro data were compared with in vivo outcome. Human PK was simulated and susceptibility breakpoints and trough levels required for optimal treatment were determined for the CLSI and EUCAST methods after 48 h and the gradient concentration MIC test strip (MTS) method after 24 h using the in vitro PK/PD relationship and Monte Carlo simulation. The in vitro PK/PD target (95% CI) associated with 50% of the maximal antifungal activity (EC50) was 28.61 (16.18-50.61), close to the in vivo EC50 of 14.67 (9.31-21.58) fAUC0-24/CLSI MIC. When human PK was simulated, the EC50 was 24.7 (17.9-35.6) fAUC0-12/CLSI MIC and it was associated with 6 week survival in clinical studies of invasive pulmonary aspergillosis. Target attainment rates were ≤5% (0%-24%), 42% (16%-58%), 68% (54%-75%) and ≥79% (73%-86%) for isolates with CLSI MICs ≥2, 1, 0.5 and ≤0.25 mg/L, respectively. A trough/CLSI MIC ratio of 2 was required for optimal treatment. The susceptible/intermediate/resistant breakpoints were determined to be 0.25/0.5-1/2 mg/L for CLSI, 0.5/1-2/4 mg/L for EUCAST and 0.25/0.375-1/1.5 mg/L for MTS. These susceptibility breakpoints and target values for therapeutic drug monitoring could be used to optimize voriconazole therapy against A. fumigatus.

Determination of isavuconazole susceptibility of Aspergillus and Candida species by the EUCAST method.

Isavuconazole is a novel expanded-spectrum triazole, which has recently been approved by the FDA as an orphan drug to treat invasive aspergillosis and is currently being studied in phase III clinical trials for invasive candidiasis. The susceptibility of relatively few clinical isolates has been reported. In this study, the isavuconazole susceptibilities of 1,237 Aspergillus and 2,010 Candida geographically diverse clinical isolates were determined by EUCAST methodology at four European mycology laboratories, producing the largest multicenter data set thus far for this compound. In addition, a blinded collection of 30 cyp51A mutant Aspergillus fumigatus clinical isolates and 10 wild-type isolates was tested. From these two data sets, the following preliminary epidemiological cutoff (ECOFF) values were suggested: 2 mg/liter for Aspergillus fumigatus, Aspergillus terreus, and Aspergillus flavus; 4 mg/liter for Aspergillus niger; 0.25 mg/liter for Aspergillus nidulans; and 0.03 mg/liter for Candida albicans, Candida parapsilosis, and Candida tropicalis. Unfortunately, ECOFFs could not be determined for Candida glabrata or Candida krusei due to an unexplained interlaboratory MIC variation. For the blinded collection of A. fumigatus isolates, all MICs were ≤2 mg/liter for wild-type isolates. Differential isavuconazole MICs were observed for triazole-resistant A. fumigatus isolates with different cyp51A alterations: TR34/L98H mutants had elevated isavuconazole MICs, whereas isolates with G54 and M220 alterations had MICs in the wild-type range, suggesting that the efficacy of isavuconazole may not be affected by these alterations. This study will be an aid in interpreting isavuconazole MICs for clinical care and an important step in the future process of setting official clinical breakpoints.

Activity of MK-3118, a new oral glucan synthase inhibitor, tested against Candida spp. by two international methods (CLSI and EUCAST)

To evaluate the activity of the orally bioavailable enfumafungin derivative MK-3118 and comparator antifungal agents tested against a collection of 113 clinical isolates of Candida spp. using CLSI and EUCAST broth microdilution (BMD) methods. Candida spp. isolates (n=113) were tested by CLSI and EUCAST methods. The collection contained 29 Candida albicans, 29 Candida glabrata, 21 Candida tropicalis, 15 Candida parapsilosis and 19 Candida krusei, including azole- and echinocandin-resistant isolates. CLSI and EUCAST MIC endpoints of 50% and 100% inhibition were determined using visual reading at 24 and 48 h of incubation and spectrophotometric reading at 24 h of incubation, respectively. MK-3118 CLSI MIC results ranged from 0.06 to 16 mg/L depending on species, duration of incubation and endpoint criteria (EC) used. Comparison of CLSI and EUCAST following 24 h of incubation and either 50% or 100% inhibition revealed an essential agreement (EA; ± 2 doubling dilutions) of 99.1% using the 50% inhibition EC and 93.2% using the 100% inhibition EC. MK-3118 (24 h of incubation and 50% EC) was active against all the species tested and displayed similar potency to caspofungin (using CLSI BMD) against C. albicans (MIC90, 1 and 2 mg/L, respectively), C. tropicalis (1 and 1 mg/L, respectively), C. parapsilosis (0.5 and 0.5 mg/L, respectively) and C. krusei (2 and 1 mg/L, respectively), but was 8-fold more potent than caspofungin against C. glabrata strains (MIC90, 2 and 16 mg/L, respectively). MK-3118 was active against fluconazole-resistant strains as well as caspofungin-resistant strains with documented fks mutations. MK-3118 was documented to have potent in vitro activity against Candida spp. when tested by both CLSI and EUCAST BMD methods, with the highest overall EA (99.1%) obtained when MK-3118 MIC results were read after 24 h of incubation using a partial inhibition EC (50%).

Evaluation of Caspofungin Susceptibility Testing by the New Vitek 2 AST-YS06 Yeast Card Using a Unique Collection of FKS Wild-Type and Hot Spot Mutant Isolates, Including the Five Most Common Candida Species

FKS mutant isolates associated with breakthrough or failure cases are emerging in clinical settings. Discrimination of these from wild-type (wt) isolates in a routine laboratory setting is complicated. We evaluated the ability of caspofungin MIC determination using the new Vitek 2 AST-Y06 yeast susceptibility card to correctly identify the fks mutants from wt isolates and compared the performance to those of the CLSI and EUCAST reference methods. A collection of 98 Candida isolates, including 31 fks hot spot mutants, were included. Performance was evaluated using the FKS genotype as the "gold standard" and compared to those of the CLSI and EUCAST methodologies. The categorical agreement for Vitek 2 was 93.9%, compared to 88.4% for the CLSI method and 98.7% for the EUCAST method. Vitek 2 misclassified 19.4% (6/31) of the fks mutant isolates as susceptible, in contrast to <4% for each of the reference methods. The overall essential agreement between the CLSI method and Vitek 2 MICs was 92.6% (88/95) but was substantially lower for fks mutant isolates (78.6% [22/28]). Correct discrimination between susceptible and intermediate Candida glabrata isolates was not possible, as the revised species-specific susceptibility breakpoint was not included in the Vitek 2 detection range (MIC of ≤0.250 to ≥4 mg/liter). In conclusion, the Vitek 2 allowed correct categorization of all wt isolates as susceptible. However, despite an acceptable categorical agreement, it failed to reliably classify isolates harboring fks hot spot mutations as intermediate or resistant, which was in part due to the fact that the detection range did not span the susceptibility breakpoint for C. glabrata.

Evaluation of the EUCAST disc diffusion susceptibility testing method for Haemophilus influenzae based on the resistance mechanism to -lactam antibiotics

EUCAST developed an antibiotic susceptibility testing method for Haemophilus influenzae. We assessed the EUCAST testing method and EUCAST clinical breakpoints and newly proposed epidemiological cut-off values against H. influenzae clinical isolates with known molecular mechanisms of resistance to β-lactam antibiotics. In total, 89 clinical isolates were used: 30 were β-lactamase negative with PBP3 mutations (gBLNAR), 20 were β-lactamase positive without PBP3 mutations (gBLPAR), 15 were β-lactamase positive with PBP3 mutations (gBLPACR), and 24 were β-lactamase negative without resistance mechanism (gBLNAS). Twelve different β-lactam antibiotics and disc charges were tested. None of the discs tested fully separated between gBLNAS and gBLNAR populations. According to EUCAST clinical zone diameter breakpoints, overall the best values of sensitivity and specificity were obtained with cefuroxime 30 μg and amoxicillin/clavulanic acid 2/1 μg discs for detection of gBLNAR and gBLPACR populations, although a previous β-lactamase test was needed. Other antibiotic discs could be suitable for epidemiological purposes, such us penicillin 10 U for separating gBLNAR isolates and cefoxitin 30 μg for detection of gBLPACR isolates. By Etest using the EUCAST method, the EUCAST MIC clinical breakpoints for ampicillin and amoxicillin/clavulanic acid showed high specificity, but low sensitivity, for the detection of genotypes with mutations in PBP3. The main genotypes of β-lactam-resistant H. influenzae can be separated by using the EUCAST disc diffusion method, although it should be noted that overlapping between populations with and without PBP3 mutations is common.

In vitro activity of isavuconazole against 208 Aspergillus flavus isolates in comparison with 7 other antifungal agents: assessment according to the methodology of the European Committee on Antimicrobial Susceptibility Testing

Aspergillus flavus is the second most common species causing invasive aspergillosis after A. fumigatus. In certain countries like India, Sudan, and Saudi Arabia, A. flavus is most frequently isolated from patients with fungal rhinosinusitis and endophthalmitis. A. flavus exhibit an increased resistance to antifungal agents compared to A. fumigatus. We determined the in vitro activity of isavuconazole, voriconazole, posaconazole, itraconazole, amphotericin B, caspofungin, micafungin, and anidulafungin against 208 isolates of A. flavus by the EUCAST method and compared with the results obtained by the CLSI method. Isavuconazole and voriconazole MICs were ≤2 μg/mL in 99% and 95%, respectively. Posaconazole and itraconazole MICs were ≤0.5 and ≤1 μg/mL, respectively, for all isolates. MICs of amphotericin B were ≥2 μg/mL in 91%; 36% of them exhibited MICs of ≥8 μg/mL. All echinocandins demonstrated good anti– A. flavus activity. The essential agreement of the MIC/MEC results by EUCAST with CLSI broth dilution method assessed at ±2 dilutions was good for itraconazole (97.8%), voriconazole (100%), posaconazole (98.3%), isavuconazole (98.9%), caspofungin (99.4%), and anidulafungin (100%), but poor for amphotericin B (53.5%) and micafungin (79.1%).

Cryptic species and azole resistance in the Aspergillus niger complex.

Aspergillus niger is a common clinical isolate. Multiple species comprise the Aspergillus section Nigri and are separable using sequence data. The antifungal susceptibility of these cryptic species is not known. We determined the azole MICs of 50 black aspergilli, 45 from clinical specimens, using modified EUCAST (mEUCAST) and Etest methods. Phylogenetic trees were prepared using the internal transcribed spacer, beta-tubulin, and calmodulin sequences to identify strains to species level and the results were compared with those obtained with cyp51A sequences. We attempted to correlate cyp51A mutations with azole resistance. Etest MICs were significantly different from mEUCAST MICs (P < 0.001), with geometric means of 0.77 and 2.79 mg/liter, respectively. Twenty-six of 50 (52%) isolates were itraconazole resistant by mEUCAST (MICs > 8 mg/liter), with limited cross-resistance to other azoles. Using combined beta-tubulin/calmodulin sequences, the 45 clinical isolates grouped into 5 clades, A. awamori (55.6%), A. tubingensis (17.8%), A. niger (13.3%), A. acidus (6.7%), and an unknown group (6.7%), none of which were morphologically distinguishable. Itraconazole resistance was found in 36% of the isolates in the A. awamori group, 90% of the A. tubingensis group, 33% of the A. niger group, 100% of the A. acidus group, and 67% of the unknown group. These data suggest that cyp51A mutations in section Nigri may not play as important a role in azole resistance as in A. fumigatus, although some mutations (G427S, K97T) warrant further study. Numerous cryptic species are found in clinical isolates of the Aspergillus section Nigri and are best reported as "A. niger complex" by clinical laboratories. Itraconazole resistance was common in this data set, but azole cross-resistance was unusual. The mechanism of resistance remains obscure.

Clinical breakpoints for voriconazole and Candida spp. revisited: review of microbiologic, molecular, pharmacodynamic, and clinical data as they pertain to the development of species-specific interpretive criteria

We reassessed the Clinical and Laboratory Standards Institute (CLSI) clinical breakpoints (CBPs) for voriconazole. We examined i) the essential (EA: ±2 dilutions) and categorical agreement between 24-h CLSI and EUCAST methods for voriconazole testing of Candida, ii) wild-type (WT) MICs and epidemiologic cutoff values (ECVs) for voriconazole by both CLSI and EUCAST methods, and iii) correlation of MICs with outcomes from previously published data using CLSI methods. We applied these findings to propose new 24-h species-specific CLSI CBPs. Adjusted 24-h CBPs for voriconazole and C. albicans, C. tropicalis, and C. parapsilosis (susceptible, ≤0.125 μg/mL; intermediate, 0.25–0.5 μg/mL; resistant, ≥1 μg/mL) should be more sensitive for detecting emerging resistance among common Candida species and provide consistency with EUCAST CBPs. In the absence of CBPs for voriconazole and C. glabrata (and less common species), we recommend that their respective ECVs be used to detect the emergence of non-WT strains.