Subcommittee on Antifungal Susceptibility Testing (AFST) of the ESCMID European Committee for Antimicrobial Susceptibility Testing (EUCAST). EUCAST definitive document EDef 7.1: method for the determination of broth dilution MICs of antifungal agents for fermentative yeasts

Recent exposure to caspofungin or fluconazole influences the epidemiology of candidemia: a prospective multicenter study involving 2,441 patients

A prospective multicenter surveillance program on yeast bloodstream infections was implemented in the Paris, France, area without restrictions on ward of hospitalization (intensive care unit, hematology, and surgery) or age (adults and children). The present analysis concerns 2,618 isolates collected over 7 years from 2,441 patients. Centralized species identification and antifungal susceptibility testing using the EUCAST methodology were performed. Almost 10% (232/2,441) of the patients had recently (≤30 days) been treated with antifungal drugs. We analyzed the effect of recent exposure to fluconazole (n = 159) or caspofungin (n = 61) on the proportions of the five major Candida species. For both drugs, preexposure was associated with a decreased prevalence of Candida albicans in favor of less drug-susceptible species (C. glabrata and C. krusei for the former and C. parapsilosis and, to a lesser extent, C. glabrata and C. krusei for the latter; P = 0.001). In the multivariate analysis, the risk of being infected with an isolate with decreased susceptibility to fluconazole was independently associated with an age of ≥15 years (odds ratio [OR] = 2.45; 95% confidence interval [CI] = 1.39 to 4.31; P = 0.002) and with recent exposure to fluconazole (OR = 2.17; 95% CI = 1.51 to 3.13; P < 0.001), while the risk of being infected with an isolate with decreased susceptibility to caspofungin was independently associated with an age <15 years (OR = 2.53; 95% CI = 1.43 to 4.48; P = 0.001) and with recent exposure to caspofungin (OR = 4.79; 95% CI = 2.47 to 9.28; P < 0.001). These findings could influence future recommendations for the management of candidemia.

Clinical Candida krusei isolates remain susceptible during extensive exposure to antifungal drugs

We have previously reported a Candida krusei outbreak during which a number of our patients were infected or colonized by several different closely related Candida krusei genotypes. The treatment response in many of our patients was at best modest and the patients remained positive for Candida krusei. We speculated that extended exposure to antifungals in patients with an incomplete treatment response might lead to the conditions for selection of drug resistance in the multiple Candida krusei clones. Therefore, we followed the in vitro susceptibility of the Candida krusei isolates taken from our patients before and during the antifungal treatment. A total of 28 Candida krusei isolates from 11 patients with prolonged exposure to antifungal medication were analyzed for their in vitro susceptibility to commonly used drugs. We found that MIC(50) values of all Candida krusei isolates was 12 microg/ml for fluconazole, 0.19 microg/ml for voriconazole, 1.0 microg/ml for amphotericin B, and 1.0 microgt/ml for caspofungin with the corresponding MIC(90) values being 16 microg/ml, 0.5 microg/ml, 2.0 microg/ml, and 1.0 micro/ml, respectively. Extended antifungal exposure did not change these MIC values. We conclude that resistance development in Candida krusei during prolonged antifungal treatment may not be common and the treatment failure of our patients was not likely due to the development of drug resistance by the etiologic agent.

Comparative evaluation of the Vitek 2 yeast susceptibility test and CLSI broth microdilution reference method for testing antifungal susceptibility of invasive fungal isolates in Italy: the GISIA3 study

The newly available AST-YS01 Vitek 2 cards were evaluated, and the results were compared with those obtained by the CLSI M27-A2 microdilution reference method. Clinical fungal isolates, including 614 isolates of Candida spp., 10 Cryptococcus neoformans isolates, 1 Geotrichum capitatum isolate, and 2 quality control strains, were tested for their susceptibilities to amphotericin B, fluconazole, and voriconazole using both methods. The majority of fungal isolates were susceptible to all antifungal agents tested: the MIC(90) values determined by the Vitek 2 and CLSI methods were 0.5 and 1 microg/ml, respectively, for amphotericin B; 8 and 16 microg/ml, respectively, for fluconazole; and <0.12 and 0.25 microg/ml, respectively, for voriconazole. Overall there was excellent categorical agreement (CA) between the methods (99.5% for amphotericin B, 92% for fluconazole, 98.2% for voriconazole), but discrepancies were observed within species. The CAs for fluconazole were low for Candida glabrata and Candida krusei when the results of the CLSI method at 48 h were considered. Moreover, the fully automated commercial system did not detect the susceptibility of Cryptococcus neoformans to voriconazole. The Vitek 2 system can be considered a valid support for antifungal susceptibility testing of fungi, but testing of susceptibility to agents not included in the system (e.g., echinocandins and posaconazole) should be performed with other methods.

Comparison of caspofungin MICs by means of EUCAST method EDef 7.1 using two different concentrations of glucose

According to the product insert for Cancidas (caspofungin acetate), the drug must not be diluted in solutions containing glucose as this decreases caspofungin stability. The aim of this study was to compare caspofungin MICs for a collection of yeasts by means of EUCAST method EDef7.1 but using two different concentrations of glucose: 2% versus 0.2%. MICs were identical or within one 2-fold dilution for 93 out of 95 strains (97.9%), showing that glucose does not interfere with susceptibility.

Antifungal activity of low molecular weight chitosan against clinical isolates of Candida spp

Chitosan is a natural polymer derived from chitin, a structural component of fungi, insects and shrimp, which exerts antimicrobial effects against bacteria and fungi. The aim of this study was to investigate the in vitro antifungal activity of low molecular weight chitosan (LMWC), and the potential synergy between chitosan and a currently used antifungal drug, fluconazole. The in vitro minimal inhibitory concentrations (MICs) of chitosan and fluconazole against 105 clinical Candida isolates were measured by the broth microdilution method. LMWC exhibited a significant antifungal activity, inhibiting over 89.9% of the clinical isolates examined (68.6% of which was completely inhibited). The species included several fluconazole-resistant strains and less susceptible species such as C. glabrata, which was inhibited at a concentration of 4.8 mg/l LMWC. Although some strains were susceptible at pH 7.0, a greater antifungal activity of LMWC was observed at pH 4.0. There was no evidence of a synergistic effect of the combination of LMWC and fluconazole at pH 7.0. This is the first report in which the antifungal activity of LMWC was investigated with clinical Candida strains. The use of LMWC as an antifungal compound opens new therapeutic perspectives, as the low toxicity of LMWC in humans supports its use in new applications in an environment of pH 4.0-4.5, such as a topical agent for vulvovaginal candidiasis.

Comparison of European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Etest methods with the CLSI broth microdilution method for echinocandin susceptibility testing of Candida species

The antifungal broth microdilution (BMD) method of the European Committee on Antibiotic Susceptibility Testing (EUCAST) and the Etest agar diffusion method were compared with the Clinical and Laboratory Standards Institute (CLSI) BMD method M27-A3 for anidulafungin, caspofungin, and micafungin susceptibility testing of 133 clinical isolates of Candida species. The isolates were characterized for the presence or absence of fks1 and/or fks2 gene mutations and included 34 isolates of C. glabrata (4 mutant strains), 32 of C. albicans (1 mutant strain), 25 of C. parapsilosis, 19 of C. guilliermondii, 12 of C. tropicalis (2 mutant strains), and 11 of C. krusei. Excellent essential agreement (EA; within 2 dilutions) between the CLSI and EUCAST and CLSI and Etest MIC results was observed. The overall EA between the EUCAST and CLSI results ranged from 89.5% (caspofungin) to 99.2% (micafungin), whereas the EA between the Etest and CLSI results ranged from 90.2% (caspofungin) to 93.2% (anidulafungin). The categorical agreement (CA) between methods for each antifungal agent was assessed using previously determined epidemiological cutoff values (ECVs). Excellent CA (>90%) was observed for all comparisons between the EUCAST and CLSI results with the exceptions of C. glabrata and caspofungin (85.3%) and C. krusei and caspofungin (54.5%). The CA between the Etest and CLSI results was also excellent for all comparisons, with the exception of C. krusei and caspofungin (81.8%). All three methods were able to differentiate wild-type (WT) strains from those with fks mutations. With anidulafungin as the test reagent, the CLSI method identified 5 of 7 mutant strains, whereas the EUCAST method and the Etest identified 6 of 7 mutant strains. With either caspofungin or micafungin as the test reagent, the CLSI method identified all 7 mutant strains and the EUCAST method identified 6 of 7 mutant strains. The Etest identified all 7 mutant strains using caspofungin as the reagent. All three test methods showed a high level of agreement and of ability to distinguish fks mutant strains of Candida species from WT strains using each of the echinocandins.

Comparison of the Vitek 2 antifungal susceptibility system with the clinical and laboratory standards institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) Broth Microdilution Reference Methods and with the Sensititre YeastOne and Etest techniques for in vitro detection of antifungal resistance in yeast isolates

The commercial technique Vitek 2 system for antifungal susceptibility testing of yeast species was evaluated. A collection of 154 clinical yeast isolates, including amphotericin B- and azole-resistant organisms, was tested. Results were compared with those obtained by the reference procedures of both the CLSI and the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Two other commercial techniques approved for clinical use, the Etest and the Sensititre YeastOne, were included in the comparative exercise as well. The average essential agreement (EA) between the Vitek 2 system and the reference procedures was >95%, comparable with the average EAs observed between the reference procedures and the Sensititre YeastOne and Etest. The EA values were >97% for Candida spp. and stood at 92% for Cryptococcus neoformans. Intraclass correlation coefficients (ICC) between the commercial techniques and the reference procedures were statistically significant (P<0.01). Percentages of very major errors were 2.6% between Vitek 2 and the EUCAST technique and 1.6% between Vitek 2 and the CLSI technique. The Vitek 2 MIC results were available after 14 to 18 h of incubation for all Candida spp. (average time to reading, 15.5 h). The Vitek 2 system was shown to be a reliable technique to determine antifungal susceptibility testing of yeast species and a more rapid and easier alternative for clinical laboratories than the procedures developed by either the CLSI or EUCAST.

Evaluation by data mining techniques of fluconazole breakpoints established by the Clinical and Laboratory Standards Institute (CLSI) and comparison with those of the European Committee on Antimicrobial Susceptibility Testing (EUCAST)

The EUCAST and the CLSI have established different breakpoints for fluconazole and Candida spp. However, the reference methodologies employed to obtain the MICs provide similar results. The aim of this work was to apply supervised classification algorithms to analyze the clinical data used by the CLSI to establish fluconazole breakpoints for Candida infections and to compare these data with the results obtained with the data set used to set up EUCAST fluconazole breakpoints, where the MIC for detecting failures was >4 mg/liter, with a sensitivity of 87%, a false-positive rate of 8%, and an area under the receiver operating characteristic (ROC) curve of 0.89. Five supervised classifiers (J48 and CART decision trees, the OneR decision rule, the naïve Bayes classifier, and simple logistic regression) were used to analyze the original cohort of patients (Rex's data set), which was used to establish CLSI breakpoints, and a later cohort of candidemia (Clancy's data set), with which CLSI breakpoints were validated. The target variable was the outcome of the infections, and the predictor variable was the MIC or dose/MIC ratio. For Rex's data set, the MIC detecting failures was >8 mg/liter, and for Clancy's data set, the MIC detecting failures was >4 mg/liter, in close agreement with the EUCAST breakpoint (MIC > 4 mg/liter). The sensitivities, false-positive rates, and areas under the ROC curve obtained by means of CART, the algorithm with the best statistical results, were 52%, 18%, and 0.7, respectively, for Rex's data set and 65%, 6%, and 0.72, respectively, for Clancy's data set. In addition, the correlation between outcome and dose/MIC ratio was analyzed for Clancy's data set, where a dose/MIC ratio of >75 was associated with successes, with a sensitivity of 93%, a false-positive rate of 29%, and an area under the ROC curve of 0.83. This dose/MIC ratio of >75 was identical to that found for the cohorts used by EUCAST to establish their breakpoints (a dose/MIC ratio of >75, with a sensitivity of 91%, a false-positive rate of 10%, and an area under the ROC curve of 0.90).

Multicenter comparison of the ISO standard 20776-1 and the serial 2-fold dilution procedures to dilute hydrophilic and hydrophobic antifungal agents for susceptibility testing

A multicenter study was conducted to assess the accuracy of the ISO standard 20776-1 and the serial 2-fold dilution procedures for antifungal susceptibility testing. Fluconazole trays can be accurately prepared by following ISO and serial dilution schemes. However, itraconazole trays showed a significant lack of reproducibility that was independent of which method was followed.

In vitro susceptibility testing in fungi: a global perspective on a variety of methods

Candida and Aspergillus species are the most common causes of invasive fungal infections in immunocompromised patients. The introduction of new antifungal agents and recent reports of resistance emerging during treatment have highlighted the need for in vitro susceptibility testing. For some drugs, there is a supporting in vitro-in vivo correlation available from studies of clinical efficacy. Both intrinsic and emergent antifungal drug resistance are encountered. Various testing procedures have been proposed, including macrodilution and microdilution, agar diffusion, disk diffusion and Etest. Early recognition of infections caused by pathogens that are resistant to one or more antifungals is highly warranted to optimise treatment and patient outcome.

Molecular screening for Candida orthopsilosis and Candida metapsilosis among Danish Candida parapsilosis group blood culture isolates: proposal of a new RFLP profile for differentiation

Candida orthopsilosis and Candida metapsilosis are recently described species phenotypically indistinguishable from Candida parapsilosis . We evaluated phenotyping and molecular methods for the detection of these species among 79 unique blood culture isolates of the C. parapsilosis group obtained during the years 2004-2008. The isolates were screened by PCR amplification of the secondary alcohol dehydrogenase-encoding gene ( SADH) followed by digestion with the restriction enzyme Ban I, using C. parapsilosis ATCC 22019, C. orthopsilosis ATCC 96139 and C. metapsilosis ATCC 96144 as controls. Isolates with RFLP patterns distinct from C. parapsilosis were characterized by sequence analysis of the ITS1-ITS2, 26S rRNA (D1/D2) and SADH regions. Restriction patterns for the 3 species with each of 610 restriction enzymes were predicted in silico using 12 available sequences. By PCR-RFLP of the SADH gene alone, four isolates (5.1 %) had a pattern identical to the C. orthopsilosis reference strain. Sequence analysis of SADH and ITS (internal transcribed spacer) regions identified two of these isolates as C. metapsilosis. These results were confirmed by creating a phylogenetic tree based on concatenated sequences of SADH, ITS and 26S rRNA gene sequence regions. Optimal differentiation between C. parapsilosis, C. metapsilosis and C. orthopsilosis was predicted using digestion with NlaIII, producing discriminatory band sizes of: 131 and 505 bp; 74, 288 and 348 bp; and 131, 217 and 288 bp, respectively. This was confirmed using the reference strains and 79 clinical isolates. In conclusion, reliable discrimination was obtained by PCR-RFLP profile analysis of the SADH gene after digestion with NlaIII but not with BanI. C. metapsilosis and C. orthopsilosis are involved in a small but significant number of invasive infections in Denmark.

Echinocandin susceptibility testing of Candida species: comparison of EUCAST EDef 7.1, CLSI M27-A3, Etest, disk diffusion, and agar dilution methods with RPMI and isosensitest media

This study compared nine susceptibility testing methods and 12 endpoints for anidulafungin, caspofungin, and micafungin with the same collection of blinded FKS hot spot mutant (n = 29) and wild-type isolates (n = 94). The susceptibility tests included EUCAST Edef 7.1, agar dilution, Etest, and disk diffusion with RPMI-1640 plus 2% glucose (2G) and IsoSensitest-2G media and CLSI M27A-3. Microdilution plates were read after 24 and 48 h. The following test parameters were evaluated: fks hot spot mutants overlapping the wild-type distribution, distance between the two populations, number of very major errors (VMEs; fks mutants misclassified as susceptible), and major errors (MEs; wild-type isolates classified as resistant) using a wild-type-upper-limit value (WT-UL) (two twofold-dilutions higher than the MIC(50)) as the susceptibility breakpoint. The methods with the lowest number of errors (given as VMEs/MEs) across the three echinocandins were CLSI (12%/1%), agar dilution with RPMI-2G medium (14%/0%), and Etest with RPMI-2G medium (8%/3%). The fewest errors overall were observed for anidulafungin (4%/1% for EUCAST, 4%/3% for CLSI, and 3%/9% for Etest with RPMI-2G). For micafungin, VME rates of 10 to 71% were observed. For caspofungin, agar dilution with either medium was superior (VMEs/MEs of 0%/1%), while CLSI, EUCAST with IsoSensitest-2G medium, and Etest were less optimal (VMEs of 7%, 10%, and 10%, respectively). Applying the CLSI breakpoint (S Collapse

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MESH Headings

• Anidulafungin
• Antifungal Agents/pharmacology
• Candida/drug effects
• Candida/genetics
• Candidiasis/microbiology
• Caspofungin
• Culture Media
• Echinocandins/pharmacology
• Indicator Dilution Techniques
• Lipopeptides/pharmacology
• Micafungin
• Microbial Sensitivity Tests/methods
• Microbial Sensitivity Tests/standards
• Reference Standards

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Grants

• R01 AI069397 NIAID NIH HHS
• AI069397 NIAID NIH HHS

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Affiliation(s)

Maiken Cavling Arendrup Unit of Mycology and Parasitology (43/117), Statens Serum Institut, Artillerivej 5, DK-2300 Copenhagen S, Denmark.
Guillermo Garcia-Effron
Cornelia Lass-Flörl
Alicia Gomez Lopez
Juan-Luis Rodriguez-Tudela
Manuel Cuenca-Estrella
David S Perlin

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Molecular identification and susceptibility profile in vitro of the emerging pathogen Candida kefyr

Candida kefyr has been increasingly associated with bloodstream infections. This study reports on the identification and antifungal susceptibility pattern of 33 Candida isolates, identified biochemically as C. kefyr. One strain was finally identified as Candida sphaerica (Kluyveromyces lactis) by ITS sequencing. Both species seem to be emerging pathogens and highly susceptible in vitro to currently licensed antifungal compounds.

Fungal biomass is a key factor affecting polymorphonuclear leucocyte-induced hyphal damage of filamentous fungi

Previous studies have not systematically assessed the effect of fungal biomass on polymorphonuclear leucocyte (PMN)-induced hyphal damage (HD) of filamentous fungi. We hypothesised that fungal biomass is a significant factor affecting PMN-induced HD. One isolate each consisting of a volume of 2 x 10(4) conidia ml(-1) of Aspergillus fumigatus, Aspergillus flavus, Aspergillus terreus, Rhizopus oryzae, Rhizopus microsporus, Cunninghamella bertholletiae, Scedosporium prolificans and Fusarium solani were incubated for six different time periods yielding biomass values between 0.01 and 0.1 optical density (OD, 405 nm). Polymorphonuclear leucocyte were added at effector-target (E : T) ratios of 5 : 1, 10 : 1, 20 : 1, 50 : 1 and 100 : 1, and HD was assessed by XTT [2,3-bis-(2-methoxy-4-nitro-5-sulphophenyl)-2H-tetrazolium-5-carboxanilide] metabolic assay. Hyphal damage decreased with increasing biomass following the sigmoid (E(max)) model (median R(2): 0.87). Hyphal damage at 0.01 OD exceeded HD at 0.1 OD (P < 0.01) by >twofold in 64 out of 80 comparisons. The sigmoid curves were shifted to the right with higher E : T ratios; the EC(50) values (OD values showing HD halfway between maximal and minimal HD) obtained for 50 : 1 or 100 : 1 were higher than for 5 : 1 (P < 0.01). Using the same E : T ratio, interspecies differences were observed; for 5 : 1, lower EC(50) values were obtained for A. flavus and the zygomycete species. In conclusion, PMN-induced HD decreases with increasing biomass. This effect is both species-dependent and E : T ratio-dependent.

Data mining validation of fluconazole breakpoints established by the European Committee on Antimicrobial Susceptibility Testing

European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints classify Candida strains with a fluconazole MIC < or = 2 mg/liter as susceptible, those with a fluconazole MIC of 4 mg/liter as representing intermediate susceptibility, and those with a fluconazole MIC > 4 mg/liter as resistant. Machine learning models are supported by complex statistical analyses assessing whether the results have statistical relevance. The aim of this work was to use supervised classification algorithms to analyze the clinical data used to produce EUCAST fluconazole breakpoints. Five supervised classifiers (J48, Correlation and Regression Trees [CART], OneR, Naïve Bayes, and Simple Logistic) were used to analyze two cohorts of patients with oropharyngeal candidosis and candidemia. The target variable was the outcome of the infections, and the predictor variables consisted of values for the MIC or the proportion between the dose administered and the MIC of the isolate (dose/MIC). Statistical power was assessed by determining values for sensitivity and specificity, the false-positive rate, the area under the receiver operating characteristic (ROC) curve, and the Matthews correlation coefficient (MCC). CART obtained the best statistical power for a MIC > 4 mg/liter for detecting failures (sensitivity, 87%; false-positive rate, 8%; area under the ROC curve, 0.89; MCC index, 0.80). For dose/MIC determinations, the target was >75, with a sensitivity of 91%, a false-positive rate of 10%, an area under the ROC curve of 0.90, and an MCC index of 0.80. Other classifiers gave similar breakpoints with lower statistical power. EUCAST fluconazole breakpoints have been validated by means of machine learning methods. These computer tools must be incorporated in the process for developing breakpoints to avoid researcher bias, thus enhancing the statistical power of the model.

Activity profile in vitro of micafungin against Spanish clinical isolates of common and emerging species of yeasts and molds

A collection of 2,278 isolates belonging to 86 different fungal species was tested with micafungin and eight other drugs using the EUCAST procedures. Micafungin was active against species of Candida and Aspergillus (even azole-resistant species) as well as Penicillium spp., Scedosporium apiospermum, and Acremonium spp. It was inactive for species of Basidiomycota and Mucorales and for multiresistant species such as those of Fusarium.

Fenticonazole activity measured by the methods of the European Committee on Antimicrobial Susceptibility Testing and CLSI against 260 Candida vulvovaginitis isolates from two European regions and annotations on the prevalent genotypes

The activity of fenticonazole was studied against 260 West and Southeast European vulvovaginal candidiasis isolates, and low MICs were displayed. Fenticonazole was assessed by European Committee on Antimicrobial Susceptibility Testing and CLSI microdilution methods for the first time, and the results showed excellent agreement (97%) and significant interclass correlation coefficient (P < 0.0001). Also, the levels of agreement for the results for itraconazole, fluconazole, and ketoconazole were 84%, 90%, and 98% (P < 0.0001), respectively. Multilocus typing by PCR fingerprinting and subsequent cluster analysis delineated geographically associated alignments for Candida albicans and fluconazole resistance-related clusters for Candida glabrata.

[Epidemiology of candidemia: a one-year prospective observational study in the west of France]

OBJECTIVE

A one-year prospective, observational study was conducted in the west of France, to evaluate the epidemiology of candidemia.

METHOD

During the year 2004, each patient with at least one blood culture yielding Candida sp. was included. For each episode of candidemia, mycological, demographical, clinical, and therapeutic data, as well as outcome, were collected.

RESULTS

One hundred and ninety-three strains of Candida sp. were isolated in 186 patients, Candida albicans accounting for 54.9%, Candida glabrata for 18.7%, Candida parapsilosis for 12.9%, Candida tropicalis for 4.7% and Candida krusei for 4.1% of these isolates. A percentage of 84% of the Candida isolates were fully susceptible to fluconazole in vitro. Dose-dependent susceptibility or resistance to fluconazole was detected in more than one third of the Candida glabrata strains, of which 36% were also resistant to voriconazole. Two-thirds of the patients were males, and the mean age was 61.5 years. A percentage of 37% of patients were hospitalized in intensive care units. The main predisposing factors for candidemia were broad-spectrum antibiotics (75.8%), central venous catheter (72.6%), cancer or hematologic malignancy (47.3%), recent surgery (42.5%), total parenteral nutrition (37.6%). One hundred and fifty-four patients were treated with antifungal therapy, two-thirds of whom received fluconazole as first-line agent. Mortality was 49% overall, and was significantly higher in case of septic shock, advanced age, and absence of catheter removal.

Breakpoints for susceptibility testing should not divide wild-type distributions of important target species

The fluconazole MIC distributions for Candida glabrata from testing 34 different clinical isolates and performing 51 tests on a single isolate mirrored each other. Since what is perceived as biological variation in isolates without resistance mechanisms is mainly methodological variation, breakpoints which divide this distribution not only lack a sound biological basis but also result in poor reproducibility of susceptibility characterization. This makes 2, 4, 8, and possibly 16 microg/ml unsuitable breakpoints for C. glabrata and fluconazole.

Identification, antifungal susceptibility and scanning electron microscopy of a keratinolytic strain of Rhodotorula mucilaginosa: a primary causative agent of onychomycosis

Onychomycosis is a dermatological problem of high prevalence that mainly affects the hallux toenail. Onychomycosis caused by the yeast Rhodotorula mucilaginosa was identified using colony morphology, light microscopy, urease and carbohydrate metabolism in a 57-year-old immunocompetent patient from Rio de Janeiro, Brazil. High-resolution scanning electron microscopy of nail fragments, processed by a noncoating method, led to the observation with fine detail of the structures of both nail and fungus involved in the infection. Yeasts were mainly found inside grooves in the nail. Budding yeasts presented a spiral pattern of growth and blastoconidia were found in the nail groove region. Keratinase assays and keratin enzymography revealed that this isolate was highly capable of degrading keratin. Antifungal susceptibility tests showed that the fungus was susceptible to low concentrations of amphotericin B and 5-flucytosine and resistant to high concentrations of fluconazole, itraconazole, voriconazole and terbinafine. These findings showed data for the first time concerning the interaction of R. mucilaginosa in toenail infection and suggest that this emerging yeast should also be considered an opportunistic primary causative agent of onychomycosis.

Pharmacotherapy of yeast infections

The rise of immunocompromised individuals in our society has provoked a significant emergence in the number of patients affected by opportunistic pathogenic yeast. The microorganisms with a major clinical incidence are species from the genera Candida (especially Candida albicans) and Cryptococcus (particularly Cryptococcus neoformans), although there has been a significant increase in other pathogenic yeasts, such as Trichosporon spp. and Rhodotorula spp. In addition, there are an increasing number of patients infected by yeasts that were not previously considered as pathogenic, such as Saccharomyces cerevisiae. The management of these infections is complicated and is highly dependent on the susceptibility profile not only of the species but also of the strain. The available antifungal compounds belong mainly to the polyene, azole and candin families, which show a distinct spectrum of activity. This review summarizes the current knowledge about the use of the main antifungals for treating infections caused by the yeast species with the most significant clinical relevance, including the susceptibility profiles exhibited by these species in vitro.

A 10-year survey of antifungal susceptibility of candidemia isolates from intensive care unit patients in Greece

This study retrospectively reviews the susceptibility of 135 baseline ICU candidemia isolates (from 1997 to 2007) to nine antifungals as determined by the AFST-EUCAST microdilution method and identifies the most frequent causative agents of confirmed point-source candidemia outbreaks in local intensive care units. A minority of common and rare Candida species displayed decreased susceptibility to all antifungals.

Activities of antifungal agents against yeasts and filamentous fungi: assessment according to the methodology of the European Committee on Antimicrobial Susceptibility Testing

We compared the activities of antifungal agents against a wide range of yeasts and filamentous fungi. The methodology of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) for yeasts and spore-forming molds was applied; and a total of 349 clinical isolates of Candida spp., other yeast species, Aspergillus spp., and nondermatophyte non-Aspergillus spp. were investigated. The average geometric mean (GM) of the MICs of the various drugs for Candida spp. were as follows: amphotericin B (AMB), 0.55 microg/ml; liposomal amphotericin B (l-AMB); 0.35 microg/ml; itraconazole (ITC), 0.56 microg/ml; voriconazole (VRC), 0.45 microg/ml; posaconazole (POS), 0.44 microg/ml; and caspofungin (CPF), 0.45 microg/ml. The data indicated that the majority of Candida spp. were susceptible to the traditional and new antifungal drugs. For Aspergillus spp., the average GM MICs of AMB, l-AMB, ITC, VRC, POS, and CPF were 1.49 microg/ml, 1.44 microg/ml, 0.65 microg/ml, 0.34 microg/ml, 0.25 microg/ml, and 0.32 microg/ml, respectively. For the various zygomycetes, the average GM MICs of AMB, l-AMB, ITC, and POS were 1.36 microg/ml, 1.42 microg/ml, 4.37 microg/ml, and 1.65 microg/ml, respectively. Other yeastlike fungi and molds displayed various patterns of susceptibility. In general, the minimal fungicidal concentrations were 1 to 3 dilutions higher than the corresponding MICs. POS, AMB, and l-AMB showed activities against a broader range of fungi than ITC, VRC, and CPF did. Emerging pathogens such as Saccharomyces cerevisiae and Fusarium solani were not killed by any drug. In summary, the EUCAST data showed that the in vitro susceptibilities of yeasts and filamentous fungi are variable, that susceptibility occurs among and within various genera and species, and that susceptibility depends on the antifungal drug tested. AMB, l-AMB, and POS were active against the majority of pathogens, including species that cause rare and difficult-to-treat infections.

Fatal-stroke syndrome revealing fungal cerebral vasculitis due to Arthrographis kalrae in an immunocompetent patient

We report an uncommon clinical presentation of a unique case of fatal invasive fungal cerebral vasculitis due to Arthrographis kalrae in a nonimmunocompromised host. The identity of the fungus was determined by morphological characteristics and by analysis of internal transcribed spacer 1 sequences and was confirmed by postmortem examination of the brain tissues. Establishing rapidly the link between the clinical syndromes and the fungal infection of the central nervous system is essential to improve the outcome. As our case has shown, it is more challenging to make a diagnosis of fungal infection when there are no risk factors of immunodeficiency and when the clinical presentation seems uncommon.

Mutations in the fks1 gene in Candida albicans, C. tropicalis, and C. krusei correlate with elevated caspofungin MICs uncovered in AM3 medium using the method of the European Committee on Antibiotic Susceptibility Testing

Mutations in two specific regions of the Fks1 subunit of 1,3-beta-D-glucan synthase are known to confer decreased caspofungin susceptibility on Candida spp. Clinical isolates of Candida spp. (404 Candida albicans, 62 C. tropicalis, and 21 C. krusei isolates) sent to the French National Reference Center were prospectively screened for susceptibility to caspofungin in vitro by the broth microdilution reference method of the Antifungal Susceptibility Testing Subcommittee of the European Committee on Antibiotic Susceptibility Testing (AFST-EUCAST). Twenty-eight isolates (25 C. albicans, 2 C. tropicalis, and 1 C. krusei isolate) for which the caspofungin MIC was above the MIC that inhibited 90% of the isolates of the corresponding species (MIC(90)) were subjected to molecular analysis in order to identify mutations in the fks1 gene. Substitutions in the deduced protein sequence of Fks1 were found for 8 isolates, and 20 isolates had the wild-type sequence. Among the six C. albicans isolates harboring mutations, six patterns were observed involving amino acid changes at positions 641, 645, 649, and 1358. For C. tropicalis, one isolate showed an L644W mutation, and for one C. krusei isolate, two mutations, L658W and L701M, were found. Two media, RPMI medium and AM3, were tested for their abilities to distinguish between isolates with wild-type Fks1 and those with mutant Fks1. In RPMI medium, caspofungin MICs ranged from 0.25 to 2 microg/ml for wild-type isolates and from 1 to 8 micro for mutant isolates. A sharper difference was observed in AM3: all wild-type isolates were inhibited by 0.25 micro of caspofungin, while caspofungin MICs for all mutant isolates were >or=0.5 microg/ml. These data demonstrate that clinical isolates of C. albicans, C. tropicalis, and C. krusei with decreased susceptibility to caspofungin in vitro have diverse mutations in the fks1 gene and that AM3 is potentially a better medium than RPMI for distinguishing between mutant and wild-type isolates using the AFST-EUCAST method.

Detection of caspofungin resistance in Candida spp. by Etest

The caspofungin susceptibilities of 28 Candida sp. clinical isolates, including 8 caspofungin-resistant isolates characterized by mutations in the Fks1 protein, were determined by the Etest in RPMI and AM3 media. Good discrimination between wild-type and mutant isolates was obtained. These results suggest that the Etest is valuable for the detection of caspofungin resistance in Candida spp.