Correlation between the procedure for antifungal susceptibility testing for Candida spp. of the European Committee on Antibiotic Susceptibility Testing (EUCAST) and four commercial techniques

Prevalence of Closely Related Candida albicans Species among Patients with Vulvovaginal Candidiasis in Southern Poland Based on the hwp1 Gene Amplification

Candida albicans remains the most common species isolated from women with vulvovaginal candidiasis. However, closely related species such as Candida africana and Candida dubliniensis may also occur, although they are often misidentified. The aim of the study was to confirm the phenotypic identification of C. albicans and its closely related species isolated from women with genital tract infections by amplification of the hwp1 (hyphal wall protein 1) gene in a PCR assay. We report a detailed molecular identification of C. albicans and its closely related species among 326 patients in the Małopolska region, Poland. Initial phenotypic identifications were confirmed by amplification of the hwp1 gene. Based on molecular analysis, we revealed 307 strains (94.17%) as C. albicans and 17 as C. dubliniensis (5.22%). No strain of C. africana was detected. Two patients h ad co-infection with C. albicans and C. dubliniensis (0.61%). A PCR assay targeting the hwp1 gene was reliable for correctly identifying species among the C. albicans complex.

Aspergillus Section Terrei and Antifungals: From Broth to Agar-Based Susceptibility Testing Methods

Providing timely antifungal treatment to patients suffering from life-threatening invasive fungal infections (IFIs) is essential. Due to the changing epidemiology and the emergence of antifungal resistance in Aspergillus, the most commonly responsible mold of IFIs, antifungal susceptibility testing (AFST) has become increasingly important to guide clinical decisions. This study assessed the essential agreement (EA) between broth microdilution methods (the Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST)) and the Etest of amphotericin B (AmB), liposomal amphotericin B (L-AmB), and isavuconazole (ISA) against 112 Aspergillus section Terrei. An EA within ±2 dilutions of ≥90% between the two methods was considered acceptable. Excellent EA was found between EUCAST and CLSI of AmB and ISA (98.2% and 95.5%, respectively). The correlation of Etest results and EUCAST/CLSI was not acceptable (<90%) for any tested antifungal; however, Etest and CLSI for AmB (79.6%) and ISA (77.6%) showed a higher EA than Etest and EUCAST for AmB (49.5%) and ISA (46.4%). It was concluded that the Etest method requires its own clinical breakpoints (CBPs) and epidemiological cutoff values (ECVs), and interpreting Etest results using EUCAST and CLSI-adapted CBPs and ECVs could result in misinterpretation as Etest shows lower minimum inhibitory concentrations (MICs).

Commercial Methods for Antifungal Susceptibility Testing of Yeasts: Strengths and Limitations as Predictors of Resistance

Susceptibility testing can yield variable results because it is method (commercial or reference), agent, and species dependent. Therefore, in order for results to be clinically relevant, MICs (minimal inhibitory concentrations) or MECs (minimal effective concentrations) should help in selecting the best treatment agent in the clinical setting. This is accomplished by categorical endpoints, ideally, breakpoints (BPs) and/or ECVs/ECOFFs (epidemiological cutoff values). BPs and ECVs are available by the reference methods (CLSI [Clinical and Laboratory Standards Institute] and EUCAST [European Committee on Antifungal Susceptibility Testing]) for a variety of species/agent combinations. The lack of clinical data precludes establishment of BPs for susceptibility testing by the commercial methods and ECVs have only been calculated for the Etest and SYO assays. The goal of this review is to summarize the variety of commercial methods for antifungal susceptibility testing and the potential value of Etest and SYO ECVs for detecting mutants/non-wild type (NWT) Candida isolates. Therefore, the literature search focused on publications where the commercial method, meaning MICs and ECVs, were reported for specific NWT isolates; genetic mutations have also been listed. For the Etest, the best performers recognizing the NWT were anidulafungin ECVs: 92% for the common species; 97% for C. glabrata and fluconazole ECVs, mostly for C. parapsilosis (45 NWT isolates). By the SYO, posaconazole ECVs recognized 93% of the C. albicans and 96% of the C. parapsilosis NWT isolates and micafungin ECVs 94% (mostly C. albicans and C. glabrata). Smaller sets, some with clinical data, were also listed. These are promising results for the use of both commercial methods to identify antifungal resistance (NWT isolates). However, ECVs for other species and methods need to be defined, including the C. neoformans complex and emerging species.

Molecular Characteristics of Regional Chromoblastomycosis in Guangdong, China: Epidemiological, Clinical, Antifungal Susceptibility, and Serum Cytokine Profiles of 45 Cases

Chromoblastomycosis (CBM) is a chronic disease caused by several species of dematiaceous fungi. In this study, a regional collection of 45 CBM cases was conducted in Guangdong, China, a hyper-endemic area of CBM. Epidemiology findings indicated that the mean age of cases was 61.38 ± 11.20 years, long duration ranged from 3 months to 30 years, and the gender ratio of male to female was 4.6:1. Thirteen cases (29%) declared underlying diseases. Verrucous form was the most common clinical manifestation (n = 19, 42%). Forty-five corresponding clinical strains were isolated, and 28 of them (62%) were identified as F. monophora; the remaining 17 (38%) were identified as F. nubica through ITS rDNA sequence analysis. Antifungal susceptibility tests in vitro showed low MICs in azoles (PCZ 0.015–0.25 μg/ml, VCZ 0.015–0.5 μg/ml, and ITZ 0.03–0.5 μg/ml) and TRB (0.015–1 μg/ml). Itraconazole combined with terbinafine was the main therapeutic strategy used for 31 of 45 cases, and 68% (n = 21) of them improved or were cured. Cytokine profile assays indicated upregulation of IL-4, IL-7, IL-15, IL-11, and IL-17, while downregulation of IL-1RA, MIP-1β, IL-8, and IL-16 compared to healthy donors (p < 0.05). The abnormal cytokine profiles indicated impaired immune response to eliminate fungus in CBM cases, which probably contributed to the chronic duration of this disease. In conclusion, we investigated the molecular epidemiological, clinical, and laboratory characteristics of CBM in Guangdong, China, which may assist further clinical therapy, as well as fundamental pathogenesis studies of CBM.

Comparison of Clinical Laboratory Standards Institute (CLSI) Microdilution Method and VITEK 2 Automated Antifungal Susceptibility System for the Determination of Antifungal Susceptibility of Candida Species

Introduction

Changes in the epidemiology of Candida infections, increasing resistance, and advances in treatment have increased the need to perform antifungal susceptibility testing in clinical laboratories. Standardized reference, the microbroth dilution method, and various commercial antifungal susceptibility test systems are used to determine antifungal susceptibility. This study aims to determine and compare the antifungal susceptibility of various Candida species isolated from blood cultures in our laboratory with the CLSI M27 microdilution reference method and VITEK 2 automated system (bioMérieux, Marcy-l'Étoile, France).

Methods

The antifungal susceptibility of a total of 140 Candida strains to fluconazole, voriconazole, and amphotericin B, and a total of 92 strains to anidulafungin was tested with the CLSI M27 method and the VITEK 2 automated system. For fluconazole, voriconazole, and amphotericin B, essential and categorical agreement percentages were calculated between the two methods. Because there is no anidulafungin in the VITEK 2 system, anidulafungin results obtained with CLSI were compared with micafungin only in terms of categorical agreement. In the category comparison, CLSI clinical breakpoints were used; the epidemiological cut-off values were used when they were not available. Very major error, major error, and minor error rates were calculated.

Results

In general, the minimum inhibitory concentration (MIC) values obtained with VITEK 2 for azole group drugs were found to be one-fold higher than the CLSI MICs read at the 24th hour. While the essential agreement between the two methods was >90% for amphotericin B and voriconazole, it remained at 85% for fluconazole. Overall, the best categorical agreement was obtained with amphotericin B (99.3%), and the least categorical agreement was obtained with voriconazole (85.7%). A very major error was seen with amphotericin B (0.7%) and fluconazole (0.7%) in one C. parapsilosis strain each. No resistance was detected with VITEK 2 in one C. glabrata strain found to be resistant to fluconazole by the reference method. Major and minor error rates were higher for azole drugs than amphotericin B and anidulafungin/micafungin.

Conclusion

The VITEK 2 system is a fast and highly applicable system, and with these features, it is advantageous for routine laboratories. In this study, although the error rate was not very high, one fluconazole-resistant C. parapsilosis and C. glabrata strain could not be detected with VITEK 2. The increase in data on the antifungal performance of the VITEK 2 system, which is available in many routine laboratories due to its ability to be used for bacteria identification and sensitivity, will contribute to the usability of the system for this purpose. In this study, data that will support the literature information in terms of the antifungal performance of the VITEK 2 system are presented.

Paving the Way to Overcome Antifungal Drug Resistance: Current Practices and Novel Developments for Rapid and Reliable Antifungal Susceptibility Testing

The past year has established the link between the COVID-19 pandemic and the global spread of severe fungal infections; thus, underscoring the critical need for rapid and realizable fungal disease diagnostics. While in recent years, health authorities, such as the Centers for Disease Control and Prevention, have reported the alarming emergence and spread of drug-resistant pathogenic fungi and warned against the devastating consequences, progress in the diagnosis and treatment of fungal infections is limited. Early diagnosis and patient-tailored therapy are established to be key in reducing morbidity and mortality associated with fungal (and cofungal) infections. As such, antifungal susceptibility testing (AFST) is crucial in revealing susceptibility or resistance of these pathogens and initiating correct antifungal therapy. Today, gold standard AFST methods require several days for completion, and thus this much delayed time for answer limits their clinical application. This review focuses on the advancements made in developing novel AFST techniques and discusses their implications in the context of the practiced clinical workflow. The aim of this work is to highlight the advantages and drawbacks of currently available methods and identify the main gaps hindering their progress toward clinical application.

Can We Improve Antifungal Susceptibility Testing?

Systemic antifungal agents are increasingly used for prevention or treatment of invasive fungal infections, whose prognosis remains poor. At the same time, emergence of resistant or even multi-resistant strains is of concern as the antifungal arsenal is limited. Antifungal susceptibility testing (AFST) is therefore of key importance for patient management and antifungal stewardship. Current AFST methods, including reference and commercial types, are based on growth inhibition in the presence of an antifungal, in liquid or solid media. They usually enable Minimal Inhibitory Concentrations (MIC) to be determined with direct clinical application. However, they are limited by a high turnaround time (TAT). Several innovative methods are currently under development to improve AFST. Techniques based on MALDI-TOF are promising with short TAT, but still need extensive clinical validation. Flow cytometry and computed imaging techniques detecting cellular responses to antifungal stress other than growth inhibition are also of interest. Finally, molecular detection of mutations associated with antifungal resistance is an intriguing alternative to standard AFST, already used in routine microbiology labs for detection of azole resistance in Aspergillus and even directly from samples. It is still restricted to known mutations. The development of Next Generation Sequencing (NGS) and whole-genome approaches may overcome this limitation in the near future. While promising approaches are under development, they are not perfect and the ideal AFST technique (user-friendly, reproducible, low-cost, fast and accurate) still needs to be set up routinely in clinical laboratories.

Antifungal Susceptibility Testing and Identification

The requirement for antifungal susceptibility testing is increasing given the availability of new drugs, increasing populations of individuals at risk for fungal infection, and emerging multiresistant fungi. Rapid and accurate fungal identification remains at the forefront of laboratory efforts to guide empiric therapy. Antifungal susceptibility testing methods have greatly improved, but are subject to variation in results between methods. Careful standardization, validation, and extensive training of users is essential to ensure susceptibility results are clinically useful and interpreted appropriately. Interpretive criteria for many drugs and species are still lacking, but this will continue to evolve.

Comparison of Two Commercial Colorimetric Broth Microdilution Tests for Candida Susceptibility Testing: Sensititre YeastOne versus MICRONAUT-AM

Two colorimetric broth microdilution antifungal susceptibility tests were compared, Sensititre YeastOne and MICRONAUT-AM for nine antifungal agents. One hundred clinical Candida isolates were tested, representing a realistic population for susceptibility testing in daily practice. The reproducibility characteristics were comparable. Only for fluconazole, caspofungin, 5-flucytosine and amphotericin B, an essential agreement of ≥90% could be demonstrated. Sensititre minimal inhibitory concentrations (MICs) were systematically higher than MICRONAUT MICs for all antifungals, except for itraconazole. CLSI clinical breakpoints (CBPs) and epidemiological cut-off values (ECVs) were used for Sensititre MICs while for MICRONAUT the EUCAST CBPs and ECVs were used. Only fluconazole, micafungin, and amphotericin B had a categorical agreement of ≥90%. For fluconazole, micafungin, and amphotericin B the susceptibility proportions were comparable. Susceptibility proportion of posaconazole and voriconazole was higher using the MICRONAUT system. For itraconazole and anidulafungin, the susceptibility proportion was higher using Sensititre. It was not possible to determine the true MIC values or the correctness of a S/I/R result since both commercial systems were validated against a different reference method. These findings show that there is a significant variability in susceptibility pattern and consequently on use of antifungals in daily practice, depending on the choice of commercial system.

Role and Interpretation of Antifungal Susceptibility Testing for the Management of Invasive Fungal Infections

Invasive fungal infections (IFIs) are associated with high mortality rates and timely appropriate antifungal therapy is essential for good outcomes. Emerging antifungal resistance among Candida and Aspergillus spp., the major causes of IFI, is concerning and has led to the increasing incorporation of in vitro antifungal susceptibility testing (AST) to guide clinical decisions. However, the interpretation of AST results and their contribution to management of IFIs remains a matter of debate. Specifically, the utility of AST is limited by the delay in obtaining results and the lack of pharmacodynamic correlation between minimal inhibitory concentration (MIC) values and clinical outcome, particularly for molds. Clinical breakpoints for Candida spp. have been substantially revised over time and appear to be reliable for the detection of azole and echinocandin resistance and for outcome prediction, especially for non-neutropenic patients with candidemia. However, data are lacking for neutropenic patients with invasive candidiasis and some non-albicans Candida spp. (notably emerging Candida auris). For Aspergillus spp., AST is not routinely performed, but may be indicated according to the epidemiological context in the setting of emerging azole resistance among A. fumigatus. For non-Aspergillus molds (e.g., Mucorales, Fusarium or Scedosporium spp.), AST is not routinely recommended as interpretive criteria are lacking and many confounders, mainly host factors, seem to play a predominant role in responses to antifungal therapy. This review provides an overview of the pre-clinical and clinical pharmacodynamic data, which constitute the rationale for the use and interpretation of AST testing of yeasts and molds in clinical practice.

Comparison of the Sensititre YeastOne antifungal method with the CLSI M27-A3 reference method to determine the activity of antifungal agents against clinical isolates of Candidaspp

Background and aim

Infections caused by Candida species are significantly increasing today, and invasive Candida infections are generally associated with high mortality. Early diagnosis and identification of Candida spp. is important for the determination of antifungal agents that will be used for treatment. The aim of the present study was to provide a better regimen for Candida infections in the future.

Materials and methods

TheSensititre YeastOne (SYO) method was compared with The Clinical Laboratory Standards Institute (CLSI) reference broth microdilution (BMD) testing method. Endpoints of minimal inhibitory concentrations (MICs) were determined for both methods.

Results

By using both methods, MIC values of micafungin, caspofungin, voriconazole, and fluconazole were lower than amphotericin B. The values obtained with the SYO method were in high categorical agreement for ecinocandins and amphotericin B. The results of voriconazole and fluconazole were in low categorical agreement. The categorical agreement between the SYO and the BMD results at 24 h was 82.1% for VORI and 98.4% for AMB. Values obtained with SYO method for all antifungal agents were in high essential agreement with the data of the CLSI reference BMD method. The essential agreement between the SYO and the BMD results at 24 h was 94.0% for MFG and 99.0% for AMB.

Conclusions

The SYO method was ready-to use, so it appeared to be easier and more efficient for Candida isolates.

Antifungal Susceptibility Testing: Current Approaches

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

Azole-resistant Candida blankii as a newly recognized cause of bloodstream infection

Candida blankii is a newly recognized human pathogen. Here we describe a case of bloodstream infection in a preterm neonate. The yeast was repeatedly isolated from blood, and its identity was confirmed by PCR sequencing of rDNA. Additionally, C. blankii DNA was detected directly in a blood sample. The isolates initially developed pink colonies on CHROMagar Candida which later turned into dark metallic blue similar to Candida tropicalis. Inaccurate identification by the VITEK 2 yeast identification system as Stephanoascus ciferrii and intrinsic resistance to fluconazole (MIC 12–16 μg/mL) underscore the need for its accurate identification for appropriate therapeutic management.

Evaluation of the relationship between the minimum inhibitory concentration of ceftiofur and third-generation cephalosporins in Escherichia coli isolates from food-producing animals

To enable future comparison of the antimicrobial susceptibility data between bacteria obtained from animals and humans, it is necessary to compare the relationships between minimum inhibitory concentrations (MICs) of veterinary and human medicine. We evaluated the relationship between the MIC of ceftiofur (CTF) and the MICs of other third-generation cephalosporins (TGCs): cefotaxime (CTX), cefpodoxime (CPDX), and ceftazidime (CAZ), determined by the broth microdilution method using 118 cefazolin-resistant Escherichia coli isolates from food-producing animals. Using the Clinical and Laboratory Standards Institute criteria, very major classification errors were observed only in CAZ (17.8%, 21 of 118); major and minor errors were observed in all TGCs (CTX: 0.8% [1 of 118] and 9.3% [11 of 118]; CPDX: 9.3% [11 of 118] and 6.8% [8 of 118]; CAZ: 2.5% [3 of 118] and 9.3% [11 of 118], respectively). The Spearman correlation coefficients between the MICs of CTF and CTX, CPDX, and CAZ were 0.765, 0.731, and 0.306, respectively. The sensitivity and specificity values were 100.0% and 81.8% for CTX, 99.0% and 27.3% for CPDX, and 76.0% and 86.4% for CAZ compared with CTF. The C-statistic was 0.978 for CTF and CTX, 0.953 for CPDX, and 0.798 for CAZ. For the TGCs evaluated in our study, testing for CTX susceptibility results showed the highest correlation with the results given when testing for CTF susceptibility.

Candidemia and invasive candidiasis in adults: A narrative review

Candidemia and invasive candidiasis are major causes of morbidity and mortality, and their incidence is increasing because of the growing complexity of patients. Five species of Candida (Candida albicans, Candida glabrata, Candida parapsilosis, Candida tropicalis and Candida krusei) account for more than 90% of all diagnosed cases, but their relative frequency varies depending on the population involved, geographical region, previous anti-fungal exposure, and patient age. The best evidence regarding the anti-fungal treatment for invasive candidiasis comes from randomized controlled trials in which more than 85% of the recruited patients had candidemia. In the case of less frequent forms of invasive candidiasis, the recommendations are based on retrospective studies, meta-analyses (when available) and experts' opinions. A pre-emptive approach based on biomarkers and clinical rules is recommended because of the high rate of infection-related mortality among critically ill patients.

SUSCEPTIBILITY TEST FOR FUNGI: CLINICAL AND LABORATORIAL CORRELATIONS IN MEDICAL MYCOLOGY

During recent decades, antifungal susceptibility testing has become standardized and nowadays has the same role of the antibacterial susceptibility testing in microbiology laboratories. American and European standards have been developed, as well as equivalent commercial systems which are more appropriate for clinical laboratories. The detection of resistant strains by means of these systems has allowed the study and understanding of the molecular basis and the mechanisms of resistance of fungal species to antifungal agents. In addition, many studies on the correlation of in vitro results with the outcome of patients have been performed, reaching the conclusion that infections caused by resistant strains have worse outcome than those caused by susceptible fungal isolates. These studies have allowed the development of interpretative breakpoints for Candida spp. and Aspergillus spp., the most frequent agents of fungal infections in the world. In summary, antifungal susceptibility tests have become essential tools to guide the treatment of fungal diseases, to know the local and global disease epidemiology, and to identify resistance to antifungals.

Resistance patterns and clinical significance of Candida colonization and infection in combat-related injured patients from iraq and afghanistan

BACKGROUND

Penetrating wounds with environmental contamination are associated with a range of infectious complications, including fungus. This is the first study to examine the epidemiology, resistance patterns, and outcomes of Candida infections and colonization in United States military patients injured in Iraq and Afghanistan.

METHODS

Clinical information associated with initial unique and serial Candida isolates collected from patients (June 2009-October 2013) through the Trauma Infectious Disease Outcomes Study (TIDOS) was evaluated. Susceptibilities were performed using Sensititre YeastOne (YO-9) plates and interpreted by Clinical Laboratory and Standards Institute (CLSI) and adjusted-European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria.

RESULTS

The analysis included 127 patients with 131 unique Candida isolates, of which 102 were Candida albicans and 29 non-albicans Candida spp. Overall, 99% of patients were male with a median age of 23 and an injury severity score of 22. Injuries were primarily due to blasts (77%) and sustained among personnel serving in Afghanistan (89%). There was a median of 7 days from injury to Candida isolation, and 74 isolates were associated with infection. In the multivariate analysis, non-albicans Candida spp were associated with prior antifungal exposure, blood isolates, and wound isolates (P < .01). Nonsusceptibility by CLSI and EUCAST criteria was associated with non-albicans Candida spp (P < .05). Patients with Candida isolation had a 7.1% mortality rate, compared with 1.4% from the overall TIDOS population.

CONCLUSIONS

Candida isolation from patients with penetrating war injuries may identify a population at higher risk for death. Prospective studies are needed to determine whether targeted antifungals and surgical management will affect this mortality rate.

Breakpoints for antifungal agents: an update from EUCAST focussing on echinocandins against Candida spp. and triazoles against Aspergillus spp

Candida and Aspergillus infections have emerged as significant pathogens in recent decades. During this same time, broad spectrum triazole and echinocandin antifungal agents have been developed and increasingly used. One consequence of widespread use is leading to the emergence of mutants with acquired resistance mutations. Therefore, accurate susceptibility testing and appropriate clinical breakpoints for the interpretation of susceptibility results have become increasingly important. Here we review the underlying methodology by which breakpoints have been selected by EUCAST (European Committee on Antimicrobial Susceptibility Testing). Five parameters are evaluated: dosing regimens used; EUCAST MIC distributions from multiple laboratories, species and compound specific epidemiological cut off values (upper MIC limits of wild type isolates or ECOFFs), pharmacokinetic/pharmacodynamic relationships and targets associated with outcome and finally clinical data by species and MIC when available. The general principles are reviewed followed by a detailed review of the individual aspects for Candida species and the three echinocandins and for Aspergillus and the three mould-active azoles. This review provides an update of the subcommittee on antifungal susceptibility testing (AFST) of the EUCAST methodology and summarises the current EUCAST breakpoints for Candida and Aspergillus. Recommendations about applicability of antifungal susceptibility testing in the routine setting are also included.

Use of the VITEK 2 system to identify and test the antifungal susceptibility of clinically relevant yeast species

Eleven quality control isolates (Candida albicans ATCC 64548, C. tropicalis ATCC 200956, C. glabrata ATCC 90030, C. lusitaniae ATCC 200951, C. parapsilosis ATCC 22019, C. krusei ATCC 6258, C. dubliniensis ATCC 6330, Saccharomyces cerevisiae ATCC 9763, Cryptococcus neoformans ATCC 90012, C. gattii FIOCRUZ-CPF 60, and Trichosporon mucoides ATCC 204094) and 32 bloodstream isolates, including C. albicans, C. tropicalis, C. parapsilosis, C. glabrata, C. krusei, C. guilliermondii, C. pelliculosa (Pichia anomala), C. haemulonii, C. lusitaniae, and C. kefyr were identified at the species level by the VITEK 2 system. A set of clinical isolates (32 total) were used as challenge strains to evaluate the ability of the VITEK 2 system to determine the antifungal susceptibility of yeasts compared with the CLSI and EUCAST BMD reference standards. The VITEK 2 system correctly identified 100% of the challenge strains. The identification of yeast species and the evaluation of their susceptibility profiles were performed in an automated manner by the VITEK 2 system after approximately 15 h of growth for most species of Candida. The VITEK 2 system ensures that each test is performed in a standardized manner and provides quantitative MIC results that are reproducible and accurate when compared with the BMD reference methods. This system was able to determine the MICs of amphotericin B, flucytosine, voriconazole, and fluconazole in 15 h or less for the most common clinically relevant Candida species. In addition, the VITEK 2 system could reliably identify resistance to flucytosine, voriconazole, and fluconazole and exhibits excellent quantitative and qualitative agreement with the CLSI or EUCAST broth microdilution reference methods.

[Recommendations for the diagnosis of candidemia in Latin America. Grupo Proyecto Épico]

Candidemia is one of the most frequent opportunistic mycoses worldwide. Limited epidemiological studies in Latin America indicate that incidence rates are higher in this region than in the Northern Hemisphere. Diagnosis is often made late in the infection, affecting the initiation of antifungal therapy. A more scientific approach, based on specific parameters, for diagnosis and management of candidemia in Latin America is warranted. 'Recommendations for the diagnosis and management of candidemia' are a series of manuscripts that have been developed by members of the Latin America Invasive Mycosis Network. They aim to provide a set of best-evidence recommendations for the diagnosis and management of candidemia. This publication, 'Recommendations for the diagnosis of candidemia in Latin America', was written to provide guidance to healthcare professionals on the diagnosis of candidemia, as well as on the usefulness and application of susceptibility testing in patients who have a confirmed diagnosis of candidemia. Computerized searches of existing literature were performed by PubMed. The data were extensively reviewed and analyzed by members of the group. The group also met on two occasions to pose questions, discuss conflicting views, and deliberate on a series of management recommendations. 'Recommendations for the diagnosis of candidemia in Latin America' includes diagnostic methods used to detect candidemia, Candida species identification, and susceptibility testing. The availability of methods, their costs and treatment settings are considered. This manuscript is the first of this series that deals with diagnosis and treatment of invasive candidiasis. Other publications in this series include: 'Recommendations for the management of candidemia in adults in Latin America', 'Recommendations for the management of candidemia in children in Latin America', and 'Recommendations for the management of candidemia in neonates in Latin America'.

Recommendations for the diagnosis of candidemia in Latin America. Latin America Invasive Mycosis Network

Candidemia is one of the most frequent opportunistic mycoses worldwide. Limited epidemiological studies in Latin America indicate that incidence rates are higher in this region than in the Northern Hemisphere. Diagnosis is often made late in the infection, affecting the initiation of antifungal therapy. A more scientific approach, based on specific parameters, for diagnosis and management of candidemia in Latin America is warranted. 'Recommendations for the diagnosis and management of candidemia' are a series of manuscripts that have been developed by members of the Latin America Invasive Mycosis Network. They aim to provide a set of best-evidence recommendations for the diagnosis and management of candidemia. This publication, 'Recommendations for the diagnosis of candidemia in Latin America', was written to provide guidance to healthcare professionals on the diagnosis of candidemia, as well as on the usefulness and application of susceptibility testing in patients who have a confirmed diagnosis of candidemia. Computerized searches of existing literature were performed by PubMed. The data were extensively reviewed and analyzed by members of the group. The group also met on two occasions to pose questions, discuss conflicting views, and deliberate on a series of management recommendations. 'Recommendations for the diagnosis of candidemia in Latin America' includes diagnostic methods used to detect candidemia, Candida species identification, and susceptibility testing. The availability of methods, their costs and treatment settings are considered. This manuscript is the first of this series that deals with diagnosis and treatment of invasive candidiasis. Other publications in this series include: 'Recommendations for the management of candidemia in adults in Latin America', 'Recommendations for the management of candidemia in children in Latin America', and 'Recommendations for the management of candidemia in neonates in Latin America'.

Antifungal susceptibility of invasive yeast isolates in Italy: the GISIA3 study in critically ill patients

Background

Yeasts are a common cause of invasive fungal infections in critically ill patients. Antifungal susceptibility testing results of clinically significant fungal strains are of interest to physicians, enabling them to adopt appropriate strategies for empiric and prophylactic therapies. We investigated the antifungal susceptibility of yeasts isolated over a 2-year period from hospitalised patients with invasive yeast infections.

Methods

638 yeasts were isolated from the blood, central venous catheters and sterile fluids of 578 patients on general and surgical intensive care units and surgical wards. Etest strips and Sensititre panels were used to test the susceptibility of the isolates to amphotericin B, anidulafungin, caspofungin, fluconazole, itraconazole, posaconazole and voriconazole in 13 laboratories centres (LC) and two co-ordinating centres (CC). The Clinical and Laboratory Standards Institute (CLSI) reference broth microdilution method was used at the CCs for comparison.

Results

Etest and Sensititre (LC/CC) MIC₉₀ values were, respectively: amphotericin B 0.5/0.38, 1/1 mg/L; anidulafungin 2/1.5 and 1/1 mg/L; caspofungin 1/0.75 and 0.5/0.5 mg/L; fluconazole 12/8 and 16/16 mg/L; itraconazole 1/1.5, 0.5/0.5 mg/L; posaconazole 0.5 mg/L and voriconazole 0.25 mg/L for all. The overall MIC₉₀ values were influenced by the reduced susceptibility of Candida parapsilosis isolates to echinocandins and a reduced or lack of susceptibility of Candida glabrata and Candida krusei to azoles, in particular fluconazole and itraconazole. Comparison of the LC and CC results showed good Essential Agreement (90.3% for Etest and 92.9% for Sensititre), and even higher Categorical Agreement (93.9% for Etest and 96% for Sensititre); differences were observed according to the species, method, and antifungal drug. No cross-resistance between echinocandins and triazoles was detected.

Conclusions

Our data confirm the different antifungal susceptibility patterns among species, and highlight the need to perform antifungal susceptibility testing of clinically relevant yeasts. With the exception of a few species (e.g. C. glabrata for azoles and C. parapsilosis for echinocandins), the findings of our study suggest that two of the most widely used commercial methods (Etest and Sensititre) provide valid and reproducible results.

The increased role of non-albicans species in candidaemia: results from a 3-year surveillance study

Various studies have documented a shift in species distribution in Candida bloodstream infections (BSI), but there are little data from Southeast Asia. This study was performed to determine the species epidemiology and antifungal susceptibilities of Candida species BSI in Singapore. Candida spp. from BSI were collected from a tertiary and secondary referral hospital, and an obstetrics/paediatric hospital over a 3-year period. The most common isolates were Candida albicans (36%), Candida tropicalis (27%), Candida glabrata (16%) and Candida parapsilosis (16%). Candida parapsilosis and C. albicans were predominant in the paediatric hospital, and C. albicans and C. tropicalis predominant in the other two institutions. Candida tropicalis temporarily replaced C. albicans as the predominant strain from BSI in 2006. Overall, 87.3% of Candida isolates were susceptible to fluconazole, and 10.4% classified as susceptible-dose-dependent. Fluconazole resistance was detected in C. tropicalis (3.6%), C. parapsilosis (2.1%) and C. glabrata (4.0%). Candida albicans is the predominant species isolated from BSI in Singapore. However, non-albicans species accounted for nearly two-thirds of all cases of candidaemia and the relative increase in C. tropicalis infections deserves further investigation. Resistance to fluconazole was uncommon.

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.

Mutants with heteroresistance to amphotericin B and fluconazole in Candida

Several studies have reported the occurrence of infections caused by Candida yeasts as well as the increasing prevalence of non albicans species. The aim of the present work is focused on the obtaining of heteroresistance to amphotericin B and fluconazole in Candida species using two distinct methodologies: selection and induction. Resistant samples were obtained by selective pressure using a medium with fluconazole for growth, followed by growth in a medium with amphotericin B. The selective pressure was also created beginning with growth in amphotericin B medium followed by growth in fluconazole medium. Concomitantly, samples were submitted to the induction of resistance through cultivation in increasing concentrations of fluconazole, followed by cultivation in increasing concentrations of amphotericin B. Subsequently, the induction began with amphotericin B followed by fluconazole. Three samples resistant to fluconazole and amphotericin B were obtained, two by induction (C. glabrata and C. tropicalis) and one by selection (C. tropicalis). Both C. tropicalis originated from the same wild sample. After successive transfers for drug free medium, only the sample obtained by selection was able to maintain the resistance phenotype. These results suggest that the phenotype of heteroresitance to fluconazole and amphotericin B can be produced by two methodologies: selection and induction.

Evaluation of the Neo-Sensitabs diffusion method for determining the antifungal susceptibilities of Cryptococcus gattii isolates, using three different agar media

The Neo-Sensitabs diffusion method was evaluated for determining the antifungal susceptibilities of 30 Cryptococcus gattii isolates to amphotericin B (AMB), fluconazole (FLC), itraconazole (ITC) and voriconazole (VRC). Three different culture media, Müeller-Hinton (MH), RPMI 1640 (RPMI) and Antibiotic medium 3 (AM3), all supplemented with 2% of glucose and 0.5 microg/ml of methylene blue, were tested. The tests were repeated three times on different days at three incubation times (48, 72 and 96 h). Results were compared with those obtained with the CLSI M27-A2 broth microdilution method. The degree of reproducibility of the diffusion test was 100% for VRC and ITC, 98.3-100% for AMB and 43.3-73.3% for FLC. The best reproducibility was observed at 48 h of incubation and no important differences among media were observed at any of the incubation times assayed. Between Neo-Sensitabs and the reference method, VRC showed the best agreement and ITC the worst in all conditions tested (100% and 56.7%, respectively). AMB showed a high agreement between the two methods (93.3% to 96.7%) but Neo-Sensitabs assay failed to detect resistant isolates (discrepancy classified as "very major error") in all times of incubation assayed. Only agreement between both methods for FLC was clearly affected by incubation time and media used, the best results being achieved at 48 h of incubation when MH and RPMI (80.0%, in both media) were used.

A Retrospective Analysis of Antifungal Susceptibilities of Candida Bloodstream Isolates From Singapore Hospitals

Introduction: Worldwide, Candida albicans is the most common Candida species implicated in bloodstream infections. However, the proportion of non-albicans bloodstream infections is increasing. Fluconazole resistance is known to be more common in non-albicans species, but is also reported in C. albicans. This retrospective study was performed to determine the species epidemiology of Candida bloodstream infections in Singapore hospitals, and to perform susceptibility testing to a range of antifungal drugs. Materials and Methods: Candida spp. isolated from bloodstream infections from October 2004 to December 2006 were collected from 3 participating hospitals: a tertiary referral hospital (Singapore General Hospital), a secondary referral hospital (Changi General Hospital) and an obstetrics/paediatric hospital [KK Women’s and Children’s Hospital (KKWCH)]. Isolate collection was also retrospectively extended to January 2000 for KKWCH because of the limited number of cases from this hospital. Isolates were identified by a common protocol, and antifungal susceptibility testing was performed by microbroth dilution (Sensititre One, Trek Diagnostics, United Kingdom). Results: The most common isolates were C. albicans (37%), C. tropicalis (27%) and C. glabrata (16%). There were differences in species distribution between institutions, with C. parapsilosis and C. albicans predominant in KKWCH, and C. albicans and C. tropicalis predominant in the other 2 institutions. Fluconazole resistance was detected in 3.2% of all Candida spp., and 85.3% were classified as susceptible. All C. albicans and C. parapsilosis were susceptible to fluconazole and voriconazole, while susceptibility to fluconazole was much more variable for C. glabrata and C. krusei. Conclusion: This study shows that C. albicans remains the predominant Candida species isolated from bloodstream infections in the 3 participating hospitals. However, non-albicans species accounted for nearly two-thirds of all cases of candidaemia. Resistance to fluconazole was uncommon, and was generally confined to C. krusei and C. glabrata. Key words: Antifungal agents, Antifungal drug resistance, Fungaemia

Current status of antifungal susceptibility testing methods

Antifungal susceptibility testing is a very dynamic field of medical mycology. Standardization of in vitro susceptibility tests by the Clinical and Laboratory Standards Institute (CLSI) and the European Committee for Antimicrobial Susceptibility Testing (EUCAST), and current availability of reference methods constituted the major remarkable steps in the field. Based on the established minimum inhibitory concentration (MIC) breakpoints, it is now possible to determine the susceptibilities of Candida strains to fluconazole, itraconazole, voriconazole, and flucytosine. Moreover, utility of fluconazole antifungal susceptibility tests as an adjunct in optimizing treatment of candidiasis has now been validated. While the MIC breakpoints and clinical significance of susceptibility testing for the remaining fungi and antifungal drugs remain yet unclear, modifications of the available methods as well as other methodologies are being intensively studied to overcome the present drawbacks and limitations. Among the other methods under investigation are Etest, colorimetric microdilution, agar dilution, determination of fungicidal activity, flow cytometry, and ergosterol quantitation. Etest offers the advantage of practical application and favorable agreement rates with the reference methods that are frequently above acceptable limits. However, MIC breakpoints for Etest remain to be evaluated and established. Development of commercially available, standardized colorimetric panels that are based on CLSI method parameters has added more to the antifungal susceptibility testing armamentarium. Flow cytometry, on the other hand, appears to offer rapid susceptibility testing but requires specified equipment and further evaluation for reproducibility and standardization. Ergosterol quantitation is another novel approach, which appears potentially beneficial particularly in discrimination of azole-resistant isolates from heavy trailers. The method is yet investigational and requires to be further studied. Developments in methodology and applications of antifungal susceptibility testing will hopefully provide enhanced utility in clinical guidance of antifungal therapy. However, and particularly in immunosuppressed host, in vitro susceptibility is and will remain only one of several factors that influence clinical outcome.

Reliability of the WIDERYST susceptibility testing system for detection of in vitro antifungal resistance in yeasts

This study evaluated the WIDERYST system, a commercially available computer-assisted image-processing device for the antifungal susceptibility testing of yeasts. A collection of 90 clinical isolates selected to represent ranges of susceptibilities in vitro as broad as possible was tested. An evaluation compared the results obtained by the new system with those achieved by both the Clinical and Laboratory Standards Institute (CLSI) microdilution reference procedure and the antifungal susceptibility standard of the European Committee for Antimicrobial Susceptibility Testing (EUCAST). Overall, the agreement and the correlation index between results obtained by the EUCAST method and the WIDERYST system were 89% and 0.84 (P < 0.01), respectively, and agreement and correlation index between data obtained by the CLSI procedure and the WIDERYST system were 90% and 0.86 (P < 0.01), respectively. The system was able to detect amphotericin B-resistant isolates. All Candida sp. isolates with resistance in vitro to azole agents were detected as well. The system misclassified some isolates belonging to the slowly growing genera Dipodascus and Pichia. A total of 2.7% very major errors were detected for fluconazole. The WIDERYST system is an alternative to reference procedures for antifungal susceptibility testing of clinical isolates of yeasts, particularly for Candida and Cryptococcus species.

[In vitro antifungal activity of voriconazole: New data after the first years of clinical experience]

Voriconazole has been developed to meet the increasing need for new and useful antifungal agents for the treatment of invasive mycoses. This review describes the spectrum of voriconazole antifungal activity based on data from in vitro studies published during the last three years. This survey demonstrates that voriconazole has a broad antifungal spectrum against the most common fungal pathogens being its action fungistatic for Candida and fungicidal for Aspergillus and other filamentous fungi. Overall, more than 95% of all Candida isolates tested are susceptible to voriconazole and less than 3% are resistant. Similar or even better activity rates have been described for Aspergillus, Cryptococcus and most of yeasts and moulds of medical importance. We also discuss the limitations related to the azole cross-resistance observed in some Candida glabrata isolates, the poor activity of voriconazole against Scedosporium prolificans, its activity against fungal biofilms and the great potential usefulness of combination of voriconazole with other antifungal drugs.

Antifungal susceptibility of bloodstream yeasts isolated at a public children’s hospital in Brazil: comparison of the Etest® and the AFST–EUCAST microdilution method

This study compared the minimum inhibitory concentration (MIC) results from the proposed standard methods of the Antifungal Susceptibility Testing Subcommittee of the European Committee on Antibiotic Susceptibility Testing (AFST–EUCAST) with the commercial system Etest® in the evaluation of susceptibility to flucytosine, fluconazole, itraconazole, voriconazole, and amphotericin B of 136 Candida spp. isolated from the blood of hospitalized children. The results presented a greater agreement among Etest® MICs ±2 log2 dilutions of AFST–EUCAST for fluconazole (98.1% and 96.3%) and voriconazole (100% and 100%) for Candida albicans and Candida parapsilosis . For Candida glabrata , the agreement was greater only for fluconazole (81.8%) and voriconazole (100%). For amphotericin B, the agreement between the methods was low for all species. The agreement percentage among the Etest® and AFST–EUCAST susceptibility profiles was high according to the MIC breakpoints recommended by the M27-A2 protocol for the majority of the yeasts, except for fluconazole and itraconazole against Candida tropicalis and for itraconazole against C. glabrata and Candida krusei . According to both methodologies, a great number of Candida spp. isolates showed an in vitro susceptibility to all evaluated antifungal agents. Overall, both procedures can be reliable techniques for susceptibility tests of yeasts, but the assessment of interlaboratory agreement and correlation of MICs by different methods with in vivo response are of great importance.

One year prospective survey of Candida bloodstream infections in Scotland

A 12 month survey of candidaemia in Scotland, UK, in which every Scottish hospital laboratory submitted all blood isolates of yeasts for identification, strain typing and susceptibility testing, provided 300 isolates from 242 patients, generating incidence data of 4.8 cases per 100,000 population per year and 5.9 cases per 100,000 acute occupied bed days; 27.9 % of cases occurred in intensive care units. More than half the patients with candidaemia had an underlying disease involving the abdomen, 78 % had an indwelling intravenous catheter, 62 % had suffered a bacterial infection within the 2 weeks prior to candidaemia and 37 % had undergone a laparotomy. Candida albicans was the infecting species in 50 % of cases, followed by Candida glabrata (21 %) and Candida parapsilosis (12 %). Seven cases of candidaemia were caused by Candida dubliniensis, which was more prevalent even than Candida lusitaniae and Candida tropicalis (six cases each). Among C. glabrata isolates, 55 % showed reduced susceptibility to fluconazole, but azole resistance among other species was extremely low. Multilocus sequence typing showed isolates with high similarity came from different hospitals across the country, and many different types came from the hospitals that submitted the most isolates, indicating no tendency towards hospital-specific endemic strains. Multiple isolates of C. albicans and C. glabrata from individual patients were of the same strain type with single exceptions for each species. The high prevalence of candidaemia in Scotland, relative to other population-based European studies, and the high level of reduced fluconazole susceptibility of Scottish C. glabrata isolates warrant continued future surveillance of invasive Candida infections.

Multicenter comparison of the VITEK 2 antifungal susceptibility test with the CLSI broth microdilution reference method for testing amphotericin B, flucytosine, and voriconazole against Candida spp

A fully automated commercial antifungal susceptibility test system (VITEK 2; bioMérieux, Inc., Hazelwood, MO) was compared in three different laboratories with the Clinical and Laboratory Standards Institute (formerly the NCCLS) reference broth microdilution method (BMD) by testing 2 quality control strains, 10 reproducibility strains, and 426 isolates of Candida spp. against amphotericin B, flucytosine, and voriconazole. Reference BMD MIC endpoints were established after 24 and 48 h of incubation. VITEK 2 system MIC endpoints were determined spectrophotometrically after 9.1 to 27.1 h of incubation (mean, 12 to 14 h). Excellent essential agreement (within 2 dilutions) between the VITEK 2 system and the 24- and 48-h BMD MICs was observed for all three antifungal agents: amphotericin B, 99.1% and 97%, respectively; flucytosine, 99.1% and 98.8%, respectively; and voriconazole, 96.7% and 96%, respectively. Both intra- and interlaboratory agreements were >98% for all three drugs. The overall categorical agreements between the VITEK 2 system and BMD for flucytosine and voriconazole were 98.1 to 98.6% at the 24-h BMD time point and 96.9 to 97.4% at the 48-h BMD time point. The VITEK 2 system reliably detected flucytosine and voriconazole resistance among Candida spp. and demonstrated excellent quantitative and qualitative agreement with the reference BMD method.

Molecular phylogenetics of Candida albicans

We analyzed data on multilocus sequence typing (MLST), ABC typing, mating type-like locus (MAT) status, and antifungal susceptibility for a panel of 1,391 Candida albicans isolates. Almost all (96.7%) of the isolates could be assigned by MLST to one of 17 clades. eBURST analysis revealed 53 clonal clusters. Diploid sequence type 69 was the most common MLST strain type and the founder of the largest clonal cluster, and examples were found among isolates from all parts of the world. ABC types and geographical origins showed statistically significant variations among clades by univariate analysis of variance, but anatomical source and antifungal susceptibility data were not significantly associated. A separate analysis limited to European isolates, thereby minimizing geographical effects, showed significant differences in the proportions of isolates from blood, commensal carriage, and superficial infections among the five most populous clades. The proportion of isolates with low antifungal susceptibility was highest for MAT homozygous a/a types and then alpha/alpha types and was lowest for heterozygous a/alpha types. The tree of clades defined by MLST was not congruent with trees generated from the individual gene fragments sequenced, implying a separate evolutionary history for each fragment. Analysis of nucleic acid variation among loci and within loci supported recombination. Computational haplotype analysis showed a high frequency of recombination events, suggesting that isolates had mixed evolutionary histories resembling those of a sexually reproducing species.

Candida albicans and Candida dubliniensis respond differently to echinocandin antifungal agents in vitro

Candida dubliniensis isolates tested for susceptibility to anidulafungin, caspofungin, and micafungin commonly showed artifactual regrowth and/or trailing effects with MIC tests done under conditions involving a high initial yeast concentration. The artifacts were less common with Candida albicans and seldom seen for either species under Clinical and Laboratory Standards Institute method M27-A test conditions.

Multicenter comparison of the VITEK 2 yeast susceptibility test with the CLSI broth microdilution reference method for testing fluconazole against Candida spp

A fully automated commercial antifungal susceptibility test system (VITEK 2 yeast susceptibility test; bioMerieux, Inc., Hazelwood, Mo.) was compared in three different laboratories with Clinical and Laboratory Standards Institute (CLSI) reference broth microdilution (BMD) method by testing two quality control strains and a total of 426 isolates of Candida spp. (103 to 135 clinical isolates in each laboratory plus 80 challenge isolates in one laboratory) against fluconazole. Reference BMD MIC endpoints were established after 24 and 48 h of incubation. VITEK 2 endpoints were determined spectrophotometrically after 10 to 26 h of incubation (mean, 13 h). Excellent essential agreement (within two dilutions) between the VITEK 2 and the 24- and 48-h BMD MICs was observed. The overall agreement values were 97.9 and 93.7%, respectively. Both intra- and interlaboratory agreement was 100%. The overall categorical agreement between VITEK 2 and BMD was 97.2% at the 24-h BMD time point and 88.3% at the 48-h BMD time point. Decreased categorical agreement at 48 h was attributed to trailing growth observed with Candida glabrata. The VITEK 2 system reliably detected fluconazole resistance among Candida spp. and demonstrated excellent quantitative and qualitative agreement with the reference BMD method.

In vitro methods for antifungal susceptibility testing of Trichophyton spp

In general, methods to test the susceptibility of fungi to antifungal drugs require standardized techniques, but so far there is no methodology that is widely applicable to dermatophytes. Here we introduced modifications to the protocols from documents of the National Committee for Clinical Laboratory Standards (CLSI) M38-A and the Antifungal Susceptibility Testing Subcommittee of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) that are usually applied to moulds and fermentative yeasts, in order to adjust the conditions for the growth of dermatophytes. The modifications included: growth on potato dextrose agar supplemented with 2% in-house rice flour to encourage sporulation, the addition of 2% glucose to the culture media (RPMI-1640), and an incubation temperature of 28 degrees C. In addition, the incubation period was 7d, the minimum inhibitory concentration (MIC) was defined as 80% growth inhibition endpoints for azole agents, and the inocula only contained microconidia. Results obtained by both tested methodologies were very similar to the ones reported by other researchers. MIC90 (MIC at which 90% of isolates tested were inhibited) values were identical for four out of five antifungal drugs tested and there was only a difference of one or two dilutions when MIC50 values were compared. Although the modifications introduced did not interfere with the results, more studies are necessary to establish a standard technique to test susceptibility of dermatophytes to antifungal drugs.

In vitro antifungal-drug susceptibilities of mycelial and yeast forms of Penicillium marneffei isolates in Cambodia

Penicillium marneffei infection is an important disease among human immunodeficiency virus patients in Southeast Asia. The in vitro antifungal-drug susceptibilities of 29 clinical isolates and 5 isolates from bamboo rats collected from 2002 to 2004 were determined. The P. marneffei yeast form is more susceptible than the mycelial form to amphotericin B and ketoconazole, while the mycelial and yeast forms displayed similar susceptibilities to flucytosine and itraconazole. The MICs of fluconazole were higher for both mycelial and yeast forms.

Méthodologie d’évaluation de la sensibilité in vitro aux antifongiques

During the last years, a large amount of work has been completed to improve the methods used for in vitro antifungal susceptibility testing. Reference techniques are currently available both for yeasts and filamentous fungi, but in some instances, technical improvement are needed. Etest is another well standardized method that can be used as an alternative on a routine basis in the clinical microbiology laboratory. Studies of in vitro-in vivo correlations have led to the definition of susceptibility breakpoints for yeasts for fluconazole, itraconazole, and flucytosine.

Rates of antifungal resistance among Spanish clinical isolates of Cryptococcus neoformans var. neoformans

OBJECTIVES

Activities in vitro of six antifungal agents were tested against a collection of 317 Cryptococcus neoformans var. neoformans clinical isolates.

METHODS

The procedure described in document 7.1 by the European Committee on Antibiotic Susceptibility Testing with minor modifications was employed.

RESULTS

Amphotericin B, itraconazole, voriconazole and ravuconazole exhibited a potent activity with geometric mean (GM) MICs under 0.26 mg/L. The GM MIC of flucytosine was 7.33 mg/L and that of fluconazole was 4.16 mg/L. The rates of antifungal resistance were 5.3% for amphotericin B, 0.9% for voriconazole and 3.1% for ravuconazole. Fifteen point eight per cent of strains had itraconazole MICs > or = 1 mg/L, and 46% of strains had flucytosine MICs > or = 8 mg/L. Fluconazole susceptibility (MIC < or = 8 mg/L) stood at 53.4%.

CONCLUSIONS

The percentage of fluconazole susceptibility was significantly lower than that in other surveys. Cross-resistance to itraconazole was common (33.8%) but almost the whole collection was susceptible to voriconazole and ravuconazole. These results should be confirmed with prospective and population-based surveillance programmes.