Activities of fluconazole and voriconazole against 1,586 recent clinical isolates of Candida species determined by Broth microdilution, disk diffusion, and Etest methods: report from the ARTEMIS Global Antifungal Susceptibility Program, 2001

Caspofungin Etest endpoint for Aspergillus isolates shows poor agreement with the reference minimum effective concentration

The Clinical and Laboratory Standards Institute (CLSI) M38-A2 reference broth microdilution (BMD) method for the antifungal susceptibility testing of filamentous fungi now includes guidelines for testing echinocandin activity using the minimum effective concentration (MEC) as the endpoint measurement. In this study, we compared the caspofungin Etest MIC on RPMI agar and Mueller-Hinton agar (supplemented with glucose and methylene blue [MGM]) to the BMD MEC for 345 clinical Aspergillus isolates, including A. flavus, A. fumigatus, A. nidulans, A. niger, and A. terreus. The essential agreement (+/-1 log(2) dilution) of the Etest on MGM and RPMI agar with the reference BMD MEC was 18 and 26%, respectively. The geometric mean values for BMD MEC and MGM Etest were 0.137 and 0.024 microg/ml, respectively, and the geometric mean values for BMD and RPMI agar were 0.128 and 0.031 microg/ml, respectively. Comparatively, 91% of paired MGM and RPMI Etest results were within 2 log(2) dilutions of each other and consistently produced clearly defined endpoints. In conclusion, the caspofungin Etest MIC, like the BMD MEC, is a reproducible endpoint but is markedly lower than the reference BMD. In anticipation of susceptibility breakpoint assignments, optimization studies will be required to improve the concordance of these two assays so that the potential for underreporting echinocandin resistance in Aspergillus is mitigated.

Rep1p negatively regulating MDR1 efflux pump involved in drug resistance in Candida albicans

Overexpression of MDR1 efflux pump is a major mechanism contributing to drug resistance in Candida albicans, the most common human fungal pathogen. To elucidate the regulatory pathway of drug resistance, we have identified a negative regulator of MDR1 and named it Regulator of Efflux Pump 1 (REP1). Overexpression of REP1 in Saccharomyces cerevisiae increased susceptibility to fluconazole. Furthermore, null mutations on REP1 decreased the susceptibility to antifungal drugs in C. albicans resulting from increased expression of MDR1 mRNA. Hence, Rep1p is involved in drug resistance by negatively regulating MDR1 in C. albicans.

In vitro activities of fluconazole, itraconazole and voriconazole against otomycotic fungal pathogens

OBJECTIVE

To determine the causative pathogens of otomycosis, and to evaluate the in vitro activity of antifungal agents against these pathogens.

MATERIALS AND METHODS

A total of 96 fungal isolate were taken from 92 patients suspected of otomycosis. The in vitro activity of fluconazole, itraconazole and voriconazole against otomycotic pathogens was tested using the E-test method.

RESULTS

The most common pathogen was Aspergillus fumigatus (40.6 per cent), followed by A niger (35.4 per cent), A flavus (12.5 per cent) and Candida albicans (11.5 per cent). All Aspergillus species were found to be resistant to fluconazole (minimum inhibitory concentration > or =256 microg/ml). The mean minimum inhibitory concentrations of voriconazole for A fumigatus, A niger, A flavus and C albicans were significantly lower than those of itraconazole for the same pathogens.

CONCLUSION

This study found that the most common otomycotic fungal pathogen was A fumigatus, and that voriconazole had more potent in vitro activity than itraconazole against all Aspergillus species as well as against C albicans.

[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.

Identification of Candida nivariensis and Candida bracarensis in a large global collection of Candida glabrata isolates: comparison to the literature

We analyzed 1,598 Candida glabrata isolates for the presence of the cryptic species Candida nivariensis and Candida bracarensis. Both species were very rare in this collection (0.2% prevalence), despite the number of isolates analyzed and the global distribution of the isolates. We saw no associated antifungal resistance in C. nivariensis.

In vitro activities of fluconazole and voriconazole against clinical isolates of Candida spp. determined by disk diffusion testing in Turin, Italy

The in vitro activities of fluconazole and voriconazole against 1,024 clinical isolates of Candida spp. were determined by the agar disk diffusion test using the Clinical and Laboratory Standards Institute (CLSI) M44-A guidelines. The results of this investigation demonstrated the broad-spectrum in vitro activity of voriconazole, relative to that of fluconazole, against yeasts tested, in particular fluconazole-resistant isolates, such as Candida krusei that showed high susceptibility to voriconazole. The situation in Turin, Italy, is quite similar to that of the rest of Italy, reflecting the worldwide trend.

Host factors do not influence the colonization or infection by fluconazole resistant Candida species in hospitalized patients

Nosocomial yeast infections have significantly increased during the past two decades in industrialized countries, including Taiwan. This has been associated with the emergence of resistance to fluconazole and other antifungal drugs. The medical records of 88 patients, colonized or infected with Candida species, from nine of the 22 hospitals that provided clinical isolates to the Taiwan Surveillance of Antimicrobial Resistance of Yeasts (TSARY) program in 1999 were reviewed. A total of 35 patients contributed fluconazole resistant strains [minimum inhibitory concentrations (MICs) ≧ 64 mg/l], while the remaining 53 patients contributed susceptible ones (MICs ≦ 8 mg/l). Fluconazole resistance was more frequent among isolates of Candida tropicalis (46.5%) than either C. albicans (36.8%) or C. glabrata (30.8%). There was no significant difference in demographic characteristics or underlying diseases among patients contributing strains different in drug susceptibility.

Identification and Susceptibility Profile of Candida fermentati from a worldwide collection of Candida guilliermondii clinical isolates

Candida fermentati isolates make up a small percentage of the clinical isolates of the Candida guilliermondii complex and have a global distribution pattern. With the exception that the MICs of micafungin were significantly lower, the calculated average MICs for C. fermentati were not significantly different from those for C. guilliermondii.

Candida parapsilosis, an emerging fungal pathogen

SUMMARY

Candida parapsilosis is an emerging major human pathogen that has dramatically increased in significance and prevalence over the past 2 decades, such that C. parapsilosis is now one of the leading causes of invasive candidal disease. Individuals at the highest risk for severe infection include neonates and patients in intensive care units. C. parapsilosis infections are especially associated with hyperalimentation solutions, prosthetic devices, and indwelling catheters, as well as the nosocomial spread of disease through the hands of health care workers. Factors involved in disease pathogenesis include the secretion of hydrolytic enzymes, adhesion to prosthetics, and biofilm formation. New molecular genetic tools are providing additional and much-needed information regarding C. parapsilosis virulence. The emerging information will provide a deeper understanding of C. parapsilosis pathogenesis and facilitate the development of new therapeutic approaches for treating C. parapsilosis infections.

Validation of 24-hour fluconazole MIC readings versus the CLSI 48-hour broth microdilution reference method: results from a global Candida antifungal surveillance program

We performed 24- and 48-h MIC determinations and disk diffusion testing of fluconazole against more than 11,000 clinical isolates of Candida species. By using the reference MIC breakpoints, the categorical agreement between the 24-h and reference 48-h broth microdilution results ranged from 93.8% (all Candida species) to 94.9% (all Candida species minus Candida krusei), with only 0.1% very major errors (VME). The essential agreement (within 2 log(2) dilutions) between the 24-h and 48-h results was 99.6%. The categorical agreement between the 24-h disk diffusion results and the 24-h MIC results, using the previously established breakpoints, was 94.4%, with 0.1% VME. Both the MIC and the disk diffusion results obtained for fluconazole after only 24 h of incubation may be used to determine the susceptibilities of Candida spp. to this widely used antifungal agent.

[Candidemia in a Brazilian tertiary care hospital: incidence, frequency of different species, risk factors and antifungal susceptibility]

Results from a cross-sectional observational study on candidemia conducted at Hospital de Clínicas, Federal University of Paraná, are presented. From January 2001 to December 2004, one hundred candidemia cases were evaluated. The incidence was 1.27 episodes per 1,000 hospitalizations and Candida was the eighth most frequently isolated agent from bloodstream infections. The patients ages ranged from five days to 89 years, with a mean of 32 years. Sixty percent of the cases occurred in adults (66% > 50 years old) and 40% in children (52% < one year old). Fifty-nine percent had been admitted to medical wards and 41% to the intensive care unit. Candida albicans was the most (59%) frequent species followed by Candida tropicalis (15%) and Candida parapsilosis (9%). The most (97%) prevalent coexisting conditions were the use of antibacterial drugs, central venous catheter (77%), H2 blockers (57%), total parenteral nutrition (49%) and admission to the intensive care unit (41%). Out of the 51 isolates tested, three of Candida glabrata presented dose-dependent susceptibility to fluconazole and resistance to itraconazole. One sample of Candida krusei presented dose-dependent susceptibility to fluconazole and one of Candida pelliculosa presented dose-dependent susceptibility to itraconazole. Among the study population, 68% received antifungal therapy, but the mortality was 56%.

Fungemia in non-HIV-infected patients: a five-year review

OBJECTIVES

To investigate the incidence, risk factors, causative fungi, and outcomes of fungemia in adult, non-HIV-infected patients.

DESIGN

We studied 147 episodes of fungemia due to Candida spp and Trichosporon spp in adult patients admitted to a university hospital in Northeast Thailand between 1999 and 2003.

RESULTS

The overall incidence of fungemia was 14.1 per 10,000 hospital admissions. Candida was the most common isolate (138 episodes, 93.9%) with non-albicans Candida accounting for 68.7%. The major non-albicans Candida isolates were Candida parapsilosis and Candida tropicalis. Fungemia caused by Trichosporon accounted for 6.1% of the cases, but their clinical features could not be distinguished from fungemia due to Candida. The overall in-hospital mortality rate was 56.1%. The independent factors related to mortality were high APACHE II score (odds ratio (OR) 1.12 per 1-point increments, 95% confidence interval (CI) 1.03-1.23), assisted ventilation (OR 3.49, 95% CI 1.04-11.64), and neutropenia (OR 7.47, 95% CI 1.25-44.74).

CONCLUSIONS

Candidemia, especially that caused by non-albicans Candida, was an important nosocomial infection in this tertiary care hospital in Northeast Thailand. The mortality rate was high, particularly in patients who were critically ill. Rapid diagnosis and early treatment are therefore important challenges for improving clinical outcomes.

Geographic distribution and antifungal susceptibility of the newly described species Candida orthopsilosis and Candida metapsilosis in comparison to the closely related species Candida parapsilosis

Candida orthopsilosis and Candida metapsilosis are recently described species, having previously been grouped with the more prevalent species Candida parapsilosis. Current literature contains very little data pertaining to the distributions and antifungal susceptibilities of these Candida species. We determined the species and antifungal susceptibilities of 1,929 invasive clinical isolates from the ARTEMIS antifungal surveillance program collected between 2001 and 2006 and identified as C. parapsilosis using Vitek and conventional methods. Of the 1,929 isolates of presumed C. parapsilosis tested, 117 (6.1%) were identified as C. orthopsilosis and 34 (1.8%) as C. metapsilosis. The percentage of presumed C. parapsilosis isolates found to be C. orthopsilosis varied greatly by region, with the highest percentage (10.9%) from South America and the lowest (0.7%) from Africa. The MIC distributions of the C. orthopsilosis and C. metapsilosis isolates were statistically significantly lower than those of C. parapsilosis for all drugs except fluconazole, for which they were significantly higher (P < 0.001 for all). No C. orthopsilosis or C. metapsilosis isolates were fluconazole resistant, and all were susceptible to caspofungin, anidulafungin, and micafungin.

Direct fluconazole susceptibility testing of positive Candida blood cultures by flow cytometry

The standard methods for yeast susceptibility testing require 24-48 h of incubation. As there has been an increase in incidence of non-albicans Candida species, the clinician is very often wary of initiating therapy with fluconazole until a final susceptibility report is generated, especially when treating very sick patients. A rapid reliable susceptibility testing method would enable the clinician to prescribe fluconazole, thus avoiding more toxic or expensive therapy. To determine the feasibility of direct susceptibility testing of Candida species to fluconazole by a rapid flow cytometric method, 50 Candida strains were seeded into blood culture bottles and were tested for susceptibility to fluconazole directly from the bottles after their being flagged as positive by the blood culture instrument. Minimal inhibitory concentration (MIC) determined by fluorescent flow cytometry (FACS) showed excellent agreement to that determined by macrodilution. Following the seeding experiments, 30 true patient specimens were tested directly from positive blood cultures, and MIC determined by both methods showed excellent agreement. Antifungal susceptibility testing by FACS directly from positive blood culture bottles is a reliable, rapid method for susceptibility testing of Candida to fluconazole. The method allows same-day results, does not require subculture to agar media, and can greatly assist in the selection of appropriate antifungal therapy.

Rhodotorula glutinis fungemia in a liver–kidney transplant patient

A 54-year-old man underwent simultaneous liver-kidney transplantation. During his prolonged hospitalization, he developed catheter-related fungemia with Rhodotorula glutinis and azole-resistant Candida glabrata. Management of the Rhodotorula fungemia was complicated by his renal insufficiency, hepatic insufficiency, and the concurrent fungemia with multi-azole resistant C. glabrata. He was treated with combination therapy with voriconazole and micafungin with subsequent clearance of the fungemia. Rhodotorula species are emerging as human pathogens with the increasing number of immunosuppressed patients in the last few decades. This is the first report of a R. glutinis fungemia in a solid organ transplant recipient.

Susceptibilities to amphotericin B and fluconazole of Candida species in Taiwan Surveillance of Antimicrobial Resistance of Yeasts 2006

Susceptibilities to amphotericin B and fluconazole of 964 Candida isolates collected in Taiwan Surveillance of Antimicrobial Resistance of Yeasts in 2006 were determined. There were 419 (43.5%) Candida albicans, 246 (25.5%) Candida tropicalis, 211 (21.9%) Candida glabrata, 62 (6.4%) Candida parapsilosis, 14 (1.5%) Candida krusei, and 12 (1.2%) others. Interestingly, 16 of the 17 amphotericin B-resistant isolates were non-albicans Candida species. The resistant rate to amphotericin B has decreased from 2.5% in 2002 to 1.8% in 2006. On the other hand, there were 132 C. tropicalis, 14 C. krusei, 10 C. albicans, and 9 C. glabrata isolates that had MICs to fluconazole > or =64 microg/mL. The prevalence of isolates with such high MICs was significantly higher than that in 2002 (17.1% versus 1.9%). Our results further indicate that most of the isolates with MICs to fluconazole > or =64 microg/mL exhibited the "trailing" phenomenon.

Antifungal susceptibility of Candida species using the Clinical and Laboratory Standards Institute disk diffusion and broth microdilution methods

There are conflicting reports on the agreement between the Clinical and Laboratory Standards Institute disk diffusion (M44-A) and reference broth microdilution (M27-A) methods for determination of antifungal susceptibility of yeasts. The antifungal susceptibility of 541 yeasts, the majority of which were from the oral cavity, was determined using these two methods and the accuracy of the disk diffusion method assessed for clinical testing of various Candida species. Of the strains tested, Candida albicans predominated (390 out of 541). The classification of susceptibility determined by the disk diffusion method was largely in concordance with that obtained using the broth dilution method, regardless of species within Candida genus. The overall observed agreement between these two methods was 94.7% for fluconazole and 96.7% for voriconazole was with a 'very major' discrepancy level of 1.5% and 1.7% respectively. This study demonstrates a strong agreement of the simple disk diffusion method with the more labour intensive 'gold standard' broth microdilution method. These findings would support the use of the disk diffusion method in a routine mycology service.

In vitro susceptibility testing of dermatophytes isolated from pediatric cases in Nigeria against five antifungals

The antifungal activities of itraconazole, ketoconazole, fluconazole, terbinafine and griseofulvin were tested by broth microdilution methods against 71 isolates of dermatophytes isolated from Nigerian children. Most drugs were very active against all the dermatophytes and the MIC 90 ranged from 0.03 to 8.0 µg/mL. This appears to be the first documented data on the antifungal susceptibility testing of isolates of dermatophytes from Nigerian children.

Fungemia at a tertiary care hospital: incidence, therapy, and distribution and antifungal susceptibility of causative species

The aim of this study was to review fungal bloodstream infections at a large tertiary care hospital to evaluate the incidence of fungemia and the distribution of causative species during the period 2001-2005. Another aim was to assess the extent of antifungal resistance. A review of all episodes of fungemia at the University Hospitals of Leuven (Belgium) was conducted between January 2001 and December 2005. For the first yeast isolate collected from each non-mould fungemic episode during a 1-year period (June 2004-June 2005), susceptibility to seven antifungal agents was determined using Sensititre YeastOne plates (Trek Diagnostic Systems, East Grinstead, UK), and the antifungal therapy was reviewed. The annual incidence of fungemia ranged between 1.30 and 1.68 episodes per 10,000 patient-days (on a total of 2,680,932 patient-days), with a decreasing trend observed over the 5-year study period. The most common species were Candida albicans (59%), Candida glabrata (22%), Candida parapsilosis (10%), and Candida tropicalis (4%). Overall, fluconazole resistance was rare (1.6%) and was detected only in C. glabrata and C. krusei. Voriconazole and caspofungin inhibited 100% of the isolates at a concentration of <or=1 microg/ml. Fluconazole was used to treat 75% of fungemic patients. Caspofungin was the second most commonly used antifungal agent (used to treat 11.7% of patients). The incidence of fungemia was higher than usually reported in other European countries. The low proportion of resistance supports the use of fluconazole as the treatment of first choice for candidemia in patients not previously exposed to this drug.

Trends in candidemia and antifungal susceptibility in a university hospital in Northern Ireland 2001-2006

OBJECTIVES

To describe the species distribution and antifungal susceptibility trends for documented episodes of candidemia at the Royal Hospitals, Belfast, 2001-2006.

METHODS

Laboratory-based retrospective observational study of all episodes of candidemia.

RESULTS

There were 151 episodes of candidemia. The species recovered were: 96 C. albicans; 26 C. glabrata; 18 C. parapsilosis; five C. tropicalis; four C. guilliermondii; one C. famata and one C. dubliniensis. We separated the data into two periods 2001-2003 and 2004-2006; contrary to the findings of other investigators, there was a notable trends toward increasing frequency of C. albicans and decreasing frequency of non-albicans species over time. Although the proportion of C. albicans, C. parapsilosis and C. tropicalis isolates susceptible to fluconazole was unchanged over time, a trend of decreased susceptibility of C. glabrata to fluconazole was noted over the six-year period. Overall, 73% and 7.7% of C. glabrata isolates had susceptible-dose-dependent and resistant phenotypes, respectively. The percentage of C. glabrata isolates susceptible to fluconazole (MIC <8 microg/ml) decreased from 36% in 2001-2003 to 0% in 2004-2006. Flucytosine resistance was detected in only 4 (2.7%) isolates. None of the isolates had an amphotericin B MIC <1 microg/ml.

CONCLUSION

A shift towards increasing dominance of C. albicans contrasts both with reports from other countries and previous data from Northern Ireland. Upwards fluconazole MIC drift among C. glabrata has important implications for empirical therapeutic decisions.

High- versus low-dose fluconazole therapy for empiric treatment of suspected invasive candidiasis among high-risk patients in the intensive care unit: a cost-effectiveness analysis

BACKGROUND

High-dose fluconazole is an alternative for patients with candidemia caused by Candida glabrata or other Candida species with decreased fluconazole susceptibility. However, empiric high-dose fluconazole is not currently recommended and may result in higher drug costs and toxicity.

OBJECTIVE

To determine the cost-effectiveness of using empiric high-dose fluconazole in intensive care unit (ICU) with suspected invasive candidiasis.

DESIGN

Decision analytic model.

TARGET POPULATION

ICU patients with suspected invasive candidiasis.

TIME HORIZON

Lifetime.

PERSPECTIVE

Societal.

INTERVENTIONS

Low-dose fluconazole (loading dose of 800 mg followed by 400 mg daily) vs. high-dose fluconazole (loading dose of 1600 mg followed by 800 mg daily). Generic fluconazole costs were used for the analysis.

OUTCOME MEASURES

Incremental life expectancy and incremental cost per discounted life year (DLY) saved. RESULT OF BASE-CASE ANALYSIS: Based on current national levels of fluconazole resistance and ability to correctly identify patients with candidemia, high-dose fluconazole was the more effective but more expensive treatment strategy. Empiric high-dose fluconazole therapy decreased the mortality rate by 0.15% compared to low-dose strategy with a cost-effectiveness rate of $55,526 per DLY saved.

RESULTS OF SENSITIVITY ANALYSIS

Empirical high-dose fluconazole was an acceptable treatment strategy (using $100,000 per DLY saved as threshold) unless the physical age of an ICU survivor was 66 years or older. Empirical high-dose fluconazole was an acceptable treatment strategy using $50,000 per DLY saved with minor changes in parameters estimates.

LIMITATIONS

The estimates of our model may not be applicable to all ICU patients. Other hospitals with differences in fluconazole resistance, prevalence of invasive candidiasis, or duration of fluconazole therapy may produce different results.

CONCLUSION

These results suggest that empiric high-dose fluconazole therapy should reduce the mortality associated with invasive candidiasis at an acceptable cost.

Differentiation of Candida albicans from non-albicans yeast directly from blood cultures by Gram stain morphology

Clusters of pseudohyphae are commonly seen on Gram stain of blood cultures from patients with Candida albicans fungemia. Whether this morphologic feature is useful for differentiating C. albicans from other yeasts has not previously been systematically evaluated. Yeast morphology on Gram stain of blood cultures from consecutive patients with fungemia detected by the Bactec automated blood culture system was prospectively assessed and correlated with the final culture-based yeast identification. The distribution of yeast in 60 consecutive patients with fungemia included Candida spp. (C. albicans 43%, Candida glabrata 28%, Candida parapsilosis 8%, Candida krusei 7%, Candida tropicalis 5%, Candida dubliniensis 2%, and Candida lusitaniae 2%), Rhodotorula mucilaginosa 2%, and Cryptococcus neoformans 3%. Upon analysis of the first positive blood culture bottle per patient, the presence of clustered pseudohyphae on Gram stain had a sensitivity, specificity, positive predictive value, and negative predictive value of 85, 97, 96, and 89%, respectively, for C. albicans. The sensitivity and specificity of aerobic vs Myco/F blood culture bottles were 96 and 95% vs 25 and 100%, p < 0.001, respectively. Inter-rater agreement for ten separate observations among five reviewers was 100%. The presence of pseudohyphae clusters by Gram stain of blood cultures is useful in distinguishing C. albicans from non-albicans yeast. Additional studies are necessary to determine the clinical impact of these findings and their validity with other blood culture systems.

Development of anidulafungin for disk diffusion susceptibility testing against Candida spp

A disk diffusion (DD) method has been standardized by the Clinical and Laboratory Standards Institute (M44-A) to test Candida susceptibilities for some azoles (fluconazole and voriconazole). The DD method using anidulafungin, a new echinocandin, was initially developed here using Candida spp. (75 strains) and candidate anidulafungin disk concentrations of 1, 2, 5, and 10 microg with or without dimethyl sulfoxide (DMSO) (0.05-1%) and with or without polysorbate 80 (P-80, 0.002-2%). The 2-microg disks (with 1% DMSO and 0.1% P-80) produced acceptable correlation statistics (r = 0.84-0.85 ) when compared with reference MIC results, and this disk was optimal for testing all Candida spp. Good separation of Candida parapsilosis (least anidulafungin-susceptible species) from the more susceptible yeast species and a potential susceptibility breakpoint near the preferred reproducible zone diameter of > or = 15 mm were achieved for all tested yeast species.

Species distribution and antifungal susceptibility of Candida bloodstream isolates in Kuwait: a 10-year study

Bloodstream infections due to Candida species are important complications in severely ill hospitalized patients. This study presents data on species distribution and antifungal susceptibility profiles of Candida bloodstream isolates obtained from Kuwait during a 10-year period. All the bloodstream isolates were identified to species level by the germ tube test and carbohydrate assimilation profile using the VITEK 2 yeast identification system. Using E-test strips for amphotericin B, fluconazole, 5-flucytosine and voriconazole, MICs were determined on RPMI agar supplemented with 2% glucose. The MIC breakpoints for resistance were based on Clinical and Laboratory Standards Institute criteria or those published by reference laboratories, and were as follows: amphotericin B, >1 microg ml-1; fluconazole, >or=64 microg ml-1; 5-flucytosine, >or=32 microg ml-1; and voriconazole, 4 microg ml-1. In all, 607 bloodstream yeast isolates were obtained over the past 10 years in Kuwait. Candida albicans was the predominant species (39.5%), followed by Candida parapsilosis (30.6%), Candida tropicalis (12.4%), Candida glabrata (5.6%) and Candida krusei (1.6%). All C. albicans, C. tropicalis and C. glabrata isolates were susceptible to amphotericin B. Of 186 isolates of C. parapsilosis tested, only four (2%) exhibited an MIC for amphotericin B of >1 microg ml-1. Resistance to fluconazole was observed in nine (3.8%) C. albicans isolates, two (5.8%) C. glabrata isolates and four (40%) C. krusei isolates. Resistance to 5-flucytosine was observed in two (0.8%) C. albicans isolates, seven (9.3%) C. tropicalis isolates, three (1.6%) C. parapsilosis isolates and all ten (100%) C. krusei isolates. All the isolates of C. albicans, C. tropicalis, C. parapsilosis, C. glabrata and C. krusei were susceptible to voriconazole, including those resistant to fluconazole. Although amphotericin B and fluconazole are widely used in clinical practice in Kuwait, resistance to these drugs remained low.

Evaluation of Etest and disk diffusion methods compared with broth microdilution antifungal susceptibility testing of clinical isolates of Candida spp. against posaconazole

We performed Etest, disk diffusion, and broth microdilution susceptibility testing of 2,171 clinical isolates of Candida spp. against posaconazole. By using provisional breakpoints for comparison purposes only, the categorical agreement between the agar-based methods and broth microdilution results ranged from 93 to 98%, with <1% very major errors. The essential agreement (within 2 well dilutions) between the Etest and broth microdilution methods was 94%. These agar-based methods hold promise as simple and reliable methods for determination of the posaconzole susceptibilities of Candida spp.

Development of novel real-time PCR assays for detection and differentiation of eleven medically important Aspergillus and Candida species in clinical specimens

In the present study, novel real-time PCR assays targeting the fungal ITS2 region were developed for the detection and differentiation of medically important Aspergillus species (Aspergillus fumigatus, Aspergillus flavus, Aspergillus nidulans, Aspergillus niger, and Aspergillus terreus) and Candida species (Candida albicans, Candida dubliniensis, Candida glabrata, Candida krusei, Candida parapsilosis, and Candida tropicalis) using a LightCycler instrument. The combination of a group-specific and a universal primer with five Aspergillus or six Candida species-specific biprobes in one reaction mixture facilitated rapid screening and species differentiation by the characteristic peak melting temperatures of the biprobes. Both assays can be performed either as single assays or simultaneously in the same LightCycler run. The analytical sensitivity using pure cultures and EDTA-anticoagulated blood, cerebrospinal fluid (CSF), and tissue samples spiked with A. fumigatus and C. albicans cell suspensions was shown to be at least 1 CFU per PCR, corresponding to 5 to 10 CFU/ml blood and 10 CFU/200 microl CSF or 0.02 g tissue. To assess the clinical applicability, 26 respiratory samples, 4 tissue samples from the maxillary sinus, and 1 blood sample were retrospectively tested and real-time PCR results were compared with results from culture, histology, or a galactomannan enzyme-linked immunosorbent assay (ELISA). Twenty samples (64.5%) were both culture positive and positive by real-time PCR. Six samples (19.4%) showed no growth of fungi but were positive by real-time PCR. However, all of the tissue samples were positive by both PCR and histology. The blood sample showed no growth of Aspergillus, but aspergillosis was confirmed by positive galactomannan ELISA, histology, and PCR results. The remaining samples (16.1%) were culture and PCR negative; also, no other signs indicating fungal infection were observed. Our data suggest that the Aspergillus and Candida assays may be appropriate for use in clinical laboratories as simple and rapid screening tests for the most frequently encountered Aspergillus and Candida species and might become an important tool in the early diagnosis of fungal infections in the future.

Correlation of Neo-Sensitabs tablet diffusion assay results on three different agar media with CLSI broth microdilution M27-A2 and disk diffusion M44-A results for testing susceptibilities of Candida spp. and Cryptococcus neoformans to amphotericin B, caspofungin, fluconazole, itraconazole, and voriconazole

We compared the Neo-Sensitabs tablet assay to both reference M27-A2 broth microdilution and M44-A disk diffusion methods for testing susceptibilities of 110 isolates of Candida spp. and Cryptococcus neoformans to amphotericin B, caspofungin, fluconazole, itraconazole, and voriconazole. Neo-Sensitabs assay inhibition zone diameters in millimeters on three agars (Mueller-Hinton agar supplemented with 2% dextrose and 0.5 microg/ml methylene blue [MGM], Shadomy [SHA], and RPMI 1640 [RPMI, 2% dextrose]) were obtained at 24 to 72 h. The correlation coefficient of Neo-Sensitabs results with MICs was similar to that of the disk method for most of the five agents on MGM (R, 0.80 to 0.89 versus 0.76 to 0.89, respectively). Overall, superior correlation was observed at 24 h for most agents. The exception was amphotericin B (R values of 0.68 and 0.5 for disk and tablet, respectively, at 48 h versus 0.68 and 0.48, respectively, at 24 h). In general, Neo-Sensitabs results were less consistent on SHA and RPMI agars. Although agreement by breakpoint category of Neo-Sensitabs and disk results with CLSI method M27-A2 was also similar on MGM (92.7 to 98.2% versus 95.5 to 100%, respectively), the Neo-Sensitabs method failed to identify two of the six isolates with high amphotericin B MICs. These data suggest the potential value of the Neo-Sensitabs assay for testing at least four of the five agents against yeasts evaluated in the clinical laboratory.

Evaluation of microdilution and disk diffusion methods for antifungal susceptibility testing of dermatophytes

A total of 63 dermatophyte strains belonging to 6 species (Trichophyton rubrum (16), T. mentagrophytes (16), T. tonsurans (20), T. violaceum (2), Microsporum canis (7), and Epidermophyton floccosum (2)) were tested for their in vitro susceptibility to a range of antifungal drugs using disk diffusion and Clinical Laboratory Standards Institute M38-A (CLSI, formerly NCCLS) broth microdilution methods. The antifungals used were ciclopirox (CIC), terbinafine (TER), griseofulvin (GRE), fluconazole (FLC), itraconazole (ITR), posaconazole (POS), and ravuconazole (RAV). In the broth microdilution assay terbinafine was found to have the highest activity followed by ravuconazole, posaconazole, ciclopirox, itraconazole, griseofulvin and fluconazole. In the disk diffusion assay terbinafine produced the largest inhibition zone diameters (IZDs) on Dermasel agar media followed by ravuconazole, griseofulvin, posaconazole, and itraconazole. A significant correlation was not observed between the minimum inhibitory concentrations (MICs) and IZDs, but some correlations were observed for POS, RAV, and TER (correlation coefficients r=-0.507, -0.249, -0.267, P<0.05, respectively). MICs obtained by the microdilution method with ITR and GRE did not correlate with IZDs obtained in disk diffusion assays in this study. The ciclopirox (20 microg/disk) and fluconazole (25 microg/disk) did not produce well defined inhibition zone diameters on Dermasel agar medium.

Nosocomial fungal infections: epidemiology, diagnosis, and treatment

Invasive fungal infections are increasingly common in the nosocomial setting. Furthermore, because risk factors for these infections continue to increase in frequency, it is likely that nosocomial fungal infections will continue to increase in frequency in the coming decades. The predominant nosocomial fungal pathogens include Candida spp., Aspergillus spp., Mucorales, Fusarium spp., and other molds, including Scedosporium spp. These infections are difficult to diagnose and cause high morbidity and mortality despite antifungal therapy. Early initiation of effective antifungal therapy and reversal of underlying host defects remain the cornerstones of treatment for nosocomial fungal infections. In recent years, new antifungal agents have become available, resulting in a change in standard of care for many of these infections. Nevertheless, the mortality of nosocomial fungal infections remains high, and new therapeutic and preventative strategies are needed.

Endogenous Candida endophthalmitis

Intraocular Candida infections, although uncommon, represent an important clinical problem owing to the potential for visual loss, which can be bilateral. Candida chorioretinitis and endophthalmitis are complications of systemic candidiasis with extension of the fungal pathogens to the uvea and retina. Early diagnosis and prompt management significantly affect the visual prognosis for these patients. This review evaluates the current literature on Candida endophthalmitis and includes discussion on presentation, diagnosis and management strategies. New systemic and intravitreal antifungal agents are also reviewed in the context of the management of intraocular fungal infection.

In VitroActivities of Voriconazole and Five Licensed Antifungal Agents AgainstCandida dubliniensis:Comparison of CLSI M27-A2, Sensititre YeastOne, Disk Diffusion, and Etest Methods

We compared the in vitro activity of six antifungal agents against 62 isolates of Candida dubliniensis by the Clinical Laboratory Standards Institute (CLSI [formerly National Committee for the Clinical Laboratory Standards]) M27-A2, Sensititre YeastOne, disk diffusion, and Etest methods and we studied the effect of the time of reading. For the azoles, voriconazole was the most potent in vitro followed by fluconazole, ketoconazole, and itraconazole. All the isolates were susceptible to amphotericin B and flucytosine. The highest rate of resistance was obtained against itraconazole with a high number of isolates defined as susceptible dose-dependent. At 24 hr, 100% of the isolates were susceptible to ketoconazole, amphotericin B, and flucytosine, 98% susceptible to voriconazole and fluconazole, and 95% for itraconazole. At 48 hr, 100% of the isolates remained susceptible for flucytosine and amphotericin B, 95% for voriconazole, 93% for fluconazole, 90% for ketoconazole, and 82% for itraconazole. The agreement between the CLSI and the other methods was better at 24 than 48 hr.

Pharmacokinetic/pharmacodynamic profile of voriconazole

Voriconazole is the first available second-generation triazole with potent activity against a broad spectrum of clinically significant fungal pathogens, including Aspergillus,Candida, Cryptococcus neoformans, and some less common moulds. Voriconazole is rapidly absorbed within 2 hours after oral administration and the oral bioavailability is over 90%, thus allowing switching between oral and intravenous formulations when clinically appropriate. Voriconazole shows nonlinear pharmacokinetics due to its capacity-limited elimination, and its pharmacokinetics are therefore dependent upon the administered dose. With increasing dose, voriconazole shows a superproportional increase in area under the plasma concentration-time curve (AUC). In doses used in children (age < 12 years) voriconazole pharmacokinetics appear to be linear. Steady-state plasma concentrations are reached approximately 5 days after both intravenous and oral administration; however, steady state is reached within 24 hours with voriconazole administered as an intravenous loading dose. The volume of distribution of voriconazole is 2-4.6 L/kg, suggesting extensive distribution into extracellular and intracellular compartments. Voriconazole was measured in tissue samples of brain, liver, kidney, heart, lung as well as cerebrospinal fluid. The plasma protein binding is about 60% and independent of dose or plasma concentrations. Clearance is hepatic via N-oxidation by the hepatic cytochrome P450 (CYP) isoenzymes, CYP2C19, CYP2C9 and CYP3A4. The elimination half-life of voriconazole is approximately 6 hours, and approximately 80% of the total dose is recovered in the urine, almost completely as metabolites. As with other azole drugs, the potential for drug interactions is considerable. Voriconazole shows time-dependent fungistatic activity against Candida species and time-dependent slow fungicidal activity against Aspergillus species. A short post-antifungal effect of voriconazole is evident only for Aspergillus species. The predictive pharmacokinetic/pharmacodynamic parameter for voriconazole treatment efficacy in Candida infections is the free drug AUC from 0 to 24 hour : minimum inhibitory concentration ratio.

The DNA-binding domain of CaNdt80p is required to activate CDR1 involved in drug resistance in Candida albicans

CaNdt80p, the Candida albicans homologue of the Saccharomyces cerevisiae transcription factor ScNdt80p, has been identified as a positive regulator of CDR1, which encodes an efflux pump involved in drug resistance in C. albicans. To investigate the involvement of the putative DNA-binding domain of CaNdt80p in drug resistance, chimeras of CaNdt80p and ScNdt80p were constructed. Interestingly, the DNA-binding domain of ScNdt80p could functionally complement that of CaNdt80p to activate CDR1p-lacZ in S. cerevisiae. Consistently, CaNdt80p containing a mutation in the DNA-binding domain failed to activate CDR1p-lacZ in S. cerevisiae. Furthermore, a copy of CaNDT80 with the same mutation also failed to complement the drug-sensitive phenotype caused by a null mutation in C. albicans. Thus, the DNA-binding domain of CaNdt80p is critical for its function in drug resistance in C. albicans.

Use of fluconazole as a surrogate marker to predict susceptibility and resistance to voriconazole among 13,338 clinical isolates of Candida spp. Tested by clinical and laboratory standards institute-recommended broth microdilution methods

Clinical laboratories frequently face the problem of delayed availability of commercially prepared approved reagents for performing susceptibility testing of new antimicrobials. Although this problem is encountered more often with antibacterial agents, it is also an issue with antifungal agents. A current example is voriconazole, a new triazole antifungal with an expanded spectrum and potency against Candida spp., Aspergillus spp., and other opportunistic fungal pathogens. The present study addresses the use of fluconazole as a surrogate marker to predict the susceptibility of Candida spp. to voriconazole. Reference broth microdilution MIC results for 13,338 strains of Candida spp. isolated from more than 200 medical centers worldwide were used. Voriconazole MICs and interpretive categories (susceptible, < or =1 microg/ml; susceptible dose dependent, 2 microg/ml; resistant, > or =4 microg/ml) were compared with those of fluconazole by regression statistics and error rate bounding analyses. For all 13,338 isolates, the absolute categorical agreement was 91.6% (false susceptible or very major error [VME], 0.0%). Since voriconazole is 16- to 32-fold more potent than fluconazole, the performance of fluconazole as a surrogate marker for voriconazole susceptibility was improved by designating those isolates with fluconazole MICs of < or =32 microg/ml as being susceptible to voriconazole, resulting in a categorical agreement of 97% with 0.1% VME. Clinical laboratories performing antifungal susceptibility testing of fluconazole against Candida spp. can reliably use these results as surrogate markers until commercial FDA-approved voriconazole susceptibility tests become available.

Biology of the pathogenic yeast Candida glabrata

The yeasts, being favorite eukaryotic microorganisms used in food industry and biotechnologies for production of biomass and various substances, are also used as model organisms in genetic manipulation, molecular and biological research. In this respect, Saccharomyces cerevisiae is the best-known species but current situation in medicine and industry requires the use of other species. Here we summarize the basic taxonomic, morphological, physiological, genetic, etc. information about the pathogenic yeast Candida glabrata that is evolutionarily very closely related to baker's yeast.

Clinical significance of azole antifungal drug cross-resistance in Candida glabrata

Candida glabrata, which can become resistant to fluconazole, is a common cause of bloodstream infection. This study was performed to determine the significance of cross-resistance to new azole drugs among C. glabrata isolates recovered as a cause of infection in azole-treated hematopoietic stem cell transplant (HSCT) recipients. Seven cases of invasive candidiasis caused by C. glabrata occurred in HSCT recipients who were receiving azole therapy between January 2000 and December 2004 in our institution. Case characteristics were ascertained. Sequential colonizing and invasive isolates were examined to determine susceptibilities to fluconazole, itraconazole, and voriconazole, and molecular relatedness by restriction fragment length polymorphism (RFLP) analysis. Twenty-three C. glabrata isolates were recovered from 4 patients who developed candidemia while receiving fluconazole and three patients who developed candidemia while receiving voriconazole. The mode MICs of fluconazole, itraconazole, and voriconazole for these isolates were > or =64 microg/ml (range, 4 to > or =64 microg/ml), 2 microg/ml (range, 0.25 to > or =16 microg/ml), and 1 microg/ml (range, 0.03 to > or =16 microg/ml), respectively. Kendall tau b correlation coefficients demonstrated significant associations between the MICs of voriconazole with fluconazole (P = 0.005) and itraconazole (P = 0.008). Colonizing and invasive isolates exhibiting variable susceptibilities had similar RFLP patterns. These observations suggest that C. glabrata exhibits considerable clinically significant cross-resistance between older azole drugs (fluconazole and itraconazole) and voriconazole. Caution is advised when considering voriconazole therapy for C. glabrata candidemia that occurs in patients with extensive prior azole drug exposure.

International surveillance of Candida spp. and Aspergillus spp.: report from the SENTRY Antimicrobial Surveillance Program (2003)

During 2003, a total of 1,397 Candida isolates, 73 Aspergillus isolates, 53 Cryptococcus neoformans isolates, and 25 other fungal isolates from infected, normally sterile, body sites in patients hospitalized in North America, Europe, and Latin America were studied as a component of the longitudinal SENTRY Antimicrobial Surveillance Program. The MICs for seven antifungal agents were determined in a central laboratory (JMI Laboratories, North Liberty, IA) using testing methods promulgated by the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards). The rank order of Candida spp. occurrence was as follows: C. albicans (48.7%), C. parapsilosis (17.3%), C. glabrata (17.2%), C. tropicalis (10.9%), C. krusei (1.9%), and other Candida spp. (4.0%). C. albicans accounted for 51.5, 47.8, and 36.5% of candidal infections in North America, Europe, and Latin America, respectively. Ravuconazole, voriconazole, and fluconazole were highly active against C. albicans, C. parapsilosis, and C. tropicalis, with both former agents being more potent (MIC at which 90% of the isolates tested are inhibited [MIC90] of < or =0.008 to 0.12 microg/ml) than fluconazole (MIC90 of 0.5 to 2 microg/ml). C. glabrata isolates were less susceptible to these agents, with MIC90s of 1, 1, and 64 microg/ml, respectively. Ravuconazole and voriconazole were the most active agents tested against C. krusei (MIC90 of 0.5 microg/ml). Among Aspergillus spp., A. fumigatus was the most commonly (71.2% of isolates) recovered species; 96.2, 96.2, 84.6, and 11.5% of strains were inhibited by < or =1 microg/ml of ravuconazole, voriconazole, itraconazole, and amphotericin B, respectively. Of the antifungal agents tested, ravuconazole and voriconazole displayed the greatest spectrum of activity against pathogenic Candida and Aspergillus spp., regardless of geographic origin. These results extend upon previous findings from SENTRY Program reports (1997 to 2000), further characterizing species composition as seen in local clinical practice and demonstrating the potent activity of selected, newer triazole antifungal agents.

Correlation of MIC with outcome for Candida species tested against voriconazole: analysis and proposal for interpretive breakpoints

Developing interpretive breakpoints for any given organism-drug combination requires integration of the MIC distribution, pharmacokinetic and pharmacodynamic parameters, and the relationship between the in vitro activity and outcome from both in vivo and clinical studies. Using data generated by standardized broth microdilution and disk diffusion test methods, the Antifungal Susceptibility Subcommittee of the Clinical and Laboratory Standards Institute has now proposed interpretive breakpoints for voriconazole and Candida species. The MIC distribution for voriconazole was determined using a collection of 8,702 clinical isolates. The overall MIC90 was 0.25 microg/ml and 99% of the isolates were inhibited at < or = 1 microg/ml of voriconazole. Similar results were obtained for 1,681 Candida isolates (16 species) from the phase III clinical trials. Analysis of the available data for 249 patients from six phase III voriconazole clinical trials demonstrated a statistically significant correlation (P = 0.021) between MIC and investigator end-of-treatment assessment of outcome. Consistent with parallel pharmacodynamic analyses, these data support the following MIC breakpoints for voriconazole and Candida species: susceptible (S), < or = 1 microg/ml; susceptible dose dependent (SDD), 2 microg/ml; and resistant (R), > or = 4 microg/ml. The corresponding disk test breakpoints are as follows: S, > or = 17 mm; SDD, 14 to 16 mm; and R, < or = 13 mm.

Use of the BIOMIC Video System to evaluate the susceptibility of clinical yeast isolates to fluconazole and voriconazole by a disk diffusion method

The ARTEMIS Global Antifungal Susceptibility Program provides the collection of epidemiological data and the results of the fluconazole and voriconazole susceptibility testing of yeast isolates. Participating in this study, a total of 7318 clinical yeast isolates were tested from different geographical areas in Hungary in the period 2001 to 2003. The species isolated most frequently was C. albicans (68.8%), followed by C. glabrata (11.8%), C. tropicalis (5.7%) and C. krusei (4.6%). Isolates of C. albicans, C. kefyr, C. lusitaniae, C. tropicalis and C. parapsilosis were highly susceptible to fluconazole (78.9-100%). The rates of isolation of fluconazole-resistant C. glabrata and C. krusei were higher in our study than the global mean in 2001 (28.2% and 87.5% vs. 18.3% and 70.2%, respectively). Differences were detected in the distribution of fluconazole-susceptibility data of C. glabrata isolates in the different counties of Hungary: most of the resistant isolates were observed in the eastern part of the country.

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.