Significant differences in drug susceptibility among species in the Candida parapsilosis group

Candida parapsilosis family has 3 proposed species: C. parapsilosis sensu stricto, Candida orthopsilosis, and Candida metapsilosis. C. parapsilosis sensu stricto had significantly higher caspofungin (CAS) and anidulafungin MICs than C. orthopsilosis or C. metapsilosis; C. metapsilosis was least susceptible to fluconazole. C. parapsilosis sensu stricto more frequently displayed (37%) paradoxical growth in CAS (P < or = 0.02). These species susceptibility differences could affect therapeutic choices.     

Susceptibility patterns of Candida species recovered from Canadian intensive care units

OBJECTIVE: The objective of this study was to determine the speciation and susceptibility patterns of Candida species recovered from Canadian intensive care units (ICUs) during a 1-day point-prevalence study on fungal colonization/infection in Canadian ICUs. METHODS AND SETTING: Blood, urine, respiratory tract, rectal, and wound fungal cultures were performed for 357 patients present at any time during a single-day 24-hour period in 35 Canadian ICUs. Comparative in vitro activities of amphotericin B, fluconazole, itraconazole, voriconazole, posaconazole, micafungin, anidulafungin, and aminocandin were determined. RESULTS: Four hundred fifteen yeasts (409 Candida species and 6 non-Candida yeasts) were recovered. Almost 50% of the patients were found to have positive respiratory tract or rectal cultures. Candida albicans accounted for 72% of the Candida species isolated, followed by Candida glabrata (16%), Candida tropicalis (5%), Candida parapsilosis (3%), Candida krusei (2%), and other Candida species or nonspeciated isolates (2%). Minimum inhibitory concentrations (milligrams per liter) at which 90% of the strains were inhibited were 0.06 for micafungin as well as anidulafungin, 0.12 for voriconazole, 0.25 for itraconazole, posaconazole, as well as aminocandin, 1 for amphotericin B, and 4 for fluconazole. Only 4% of the isolates were resistant to fluconazole and/or itraconazole. CONCLUSIONS: Candida albicans is the predominant species colonizing Canadian ICU patients. Overall, the triazoles, both older and new compounds, and the echinocandins have excellent in vitro antifungal activities against Candida species recovered from Canadian ICUs patients.     

Prevalence and susceptibility profile of Candida metapsilosis and Candida orthopsilosis: results from population-based surveillance of candidemia in Spain

We describe the prevalences and susceptibility profiles of two recently described species, Candida metapsilosis and Candida orthopsilosis, related to Candida parapsilosis in candidemia. The prevalences of these species (1.7% for C. metapsilosis and 1.4% for C. orthopsilosis) are significant. Differences observed in their susceptibility profiles could have therapeutic importance.     

Candida bloodstream infections: comparison of species distributions and antifungal resistance patterns in community-onset and nosocomial isolates in the SENTRY Antimicrobial Surveillance Program, 2008-2009

Community-onset (CO) candidemia, defined as a positive blood culture taken at or within 2 days of hospital admission, represents a distinct clinical entity associated with substantial morbidity and mortality. Reference MIC results from the SENTRY Antimicrobial Surveillance Program (2008-2009) were analyzed to compare the antifungal resistance patterns and species distributions from patients with CO and nosocomial bloodstream infections (BSI) in 79 medical centers. Among 1,354 episodes of BSI, 494 (36.5%) were classified as CO and 860 (63.5%) as nosocomial in origin. More than 95% of the isolates from both BSI types were contributed by Candida albicans (48.4%), C. glabrata (18.2%), C. parapsilosis (17.1%), C. tropicalis (10.6%), and C. krusei (2.0%). C. albicans was more common in CO BSI (51.0%) than nosocomial BSI (46.9%), whereas C. parapsilosis and C. krusei were more common in nosocomial BSIs (18.1 and 2.7%, respectively) than in CO BSIs (15.4 and 0.8%, respectively). C. glabrata and C. tropicalis were comparable in both CO (18.4 and 10.5%, respectively) and nosocomial (18.1 and 10.6%, respectively) episodes. Resistance to azoles (fluconazole, posaconazole, and voriconazole) and echinocandins (anidulafungin, caspofungin, and micafungin) was uncommon (<5%) in CO BSI using recently established Clinical and Laboratory Standards Institute breakpoint criteria. Resistance to echinocandins (anidulafungin [3.8%], caspofungin [5.1%], and micafungin [3.2%]) and azoles (fluconazole [7.7%], posaconazole [5.1%], and voriconazole [6.4%]) was most prevalent among nosocomial BSI isolates of C. glabrata. CO candidemia is not uncommon and appears to be increasing worldwide due to changing health care practices. Although resistance to the azoles and echinocandins remains uncommon among CO isolates, we demonstrate the emergence of nosocomial occurrences of C. glabrata expressing resistance to both monitored classes of antifungal agents.     

Comparison of EUCAST and CLSI broth microdilution methods for the susceptibility testing of 10 Systemically active antifungal agents when tested against Candida spp.

The antifungal broth microdilution (BMD) method of the European Committee on Antimicrobial Susceptibility Testing (EUCAST) was compared with Clinical and Laboratory Standards Institute (CLSI) BMD method M27-A3 for amphotericin B, flucytosine, anidulafungin, caspofungin, micafungin, fluconazole, isavuconazole, itraconazole, posaconazole, and voriconazole susceptibility testing of 357 isolates of Candida. The isolates were selected from global surveillance collections to represent both wild-type (WT) and non-WT MIC results for the azoles (12% of fluconazole and voriconazole results were non-WT) and the echinocandins (6% of anidulafungin and micafungin results were non-WT). The study collection included 114 isolates of Candida albicans, 73 of C. glabrata, 76 of C. parapsilosis, 60 of C. tropicalis, and 34 of C. krusei. The overall essential agreement (EA) between EUCAST and CLSI results ranged from 78.9% (posaconazole) to 99.6% (flucytosine). The categorical agreement (CA) between methods and species of Candida was assessed using previously determined CLSI epidemiological cutoff values. The overall CA between methods was 95.0% with 2.5% very major (VM) and major (M) discrepancies. The CA was >93% for all antifungal agents with the exception of caspofungin (84.6%), where 10% of the results were categorized as non-WT by the EUCAST method and WT by the CLSI method. Problem areas with low EA or CA include testing of amphotericin B, anidulafungin, and isavuconazole against C. glabrata, itraconazole, and posaconazole against most species, and caspofungin against C. parapsilosis, C. tropicalis, and C. krusei. We confirm high level EA and CA (>90%) between the 2 methods for testing fluconazole, voriconazole, and micafungin against all 5 species. The results indicate that the EUCAST and CLSI methods produce comparable results for testing the systemically active antifungal agents against the 5 most common species of Candida; however, there are several areas where additional steps toward harmonization are warranted.     

A naturally occurring proline-to-alanine amino acid change in Fks1p in Candida parapsilosis, Candida orthopsilosis, and Candida metapsilosis accounts for reduced echinocandin susceptibility

Candida parapsilosis has emerged as a common cause of invasive fungal infection, especially in Latin America and in the neonatal setting. C. parapsilosis is part of a closely related group of organisms that includes the species Candida orthopsilosis and Candida metapsilosis. All three species show elevated MICs for the new echinocandin class drugs caspofungin, micafungin, and anidulafungin relative to other Candida species. Despite potential impacts on therapy, the mechanism behind this reduced echinocandin susceptibility has not been determined. In this report, we investigated the role of a naturally occurring Pro-to-Ala substitution at amino acid position 660 (P660A), immediately distal to the highly conserved hot spot 1 region of Fks1p, in the reduced-echinocandin-susceptibility phenotype. Kinetic inhibition studies demonstrated that glucan synthase from the C. parapsilosis group was 1 to 2 logs less sensitive to echinocandin drugs than the reference enzyme from C. albicans. Furthermore, clinical isolates of C. albicans and C. glabrata which harbor mutations at this equivalent position also showed comparable 2-log decreases in target enzyme sensitivity, which correlated with increased MICs. These mutations also resulted in 2.4- to 18.8-fold-reduced V(max) values relative to those for the wild-type enzyme, consistent with kinetic parameters obtained for C. parapsilosis group enzymes. Finally, the importance of the P660A substitution for intrinsic resistance was confirmed by engineering an equivalent P647A mutation into Fks1p of Saccharomyces cerevisiae. The mutant glucan synthase displayed characteristic 2-log decreases in sensitivity to the echinocandin drugs. Overall, these data firmly indicate that a naturally occurring P660A substitution in Fks1p from the C. parapsilosis group accounts for the reduced susceptibility phenotype.     

Antifungal susceptibility survey of 2,000 bloodstream Candida isolates in the United States

Candida bloodstream isolates (n = 2,000) from two multicenter clinical trials carried out by the National Institute of Allergy and Infectious Diseases Mycoses Study Group between 1995 and 1999 were tested against amphotericin B (AMB), flucytosine (5FC), fluconazole (FLU), itraconazole (ITR), voriconazole (VOR), posaconazole (POS), caspofungin (CFG), micafungin (MFG), and anidulafungin (AFG) using the NCCLS M27-A2 microdilution method. All drugs were tested in the NCCLS-specified RPMI 1640 medium except for AMB, which was tested in antibiotic medium 3. A sample of isolates was also tested in RPMI 1640 supplemented to 2% glucose and by using the diluent polyethylene glycol (PEG) in lieu of dimethyl sulfoxide for those drugs insoluble in water. Glucose supplementation tended to elevate the MIC, whereas using PEG tended to decrease the MIC. Trailing growth occurred frequently with azoles. Isolates were generally susceptible to AMB, 5FC, and FLU. Rates of resistance to ITR approached 20%. Although no established interpretative breakpoints are available for the candins (CFG, MFG, and AFG) and the new azoles (VOR and POS), they all exhibited excellent antifungal activity, even for those strains resistant to the other aforementioned agents.     

Differential activities of newer antifungal agents against Candida albicans and Candida parapsilosis biofilms

The activities of voriconazole, posaconazole, caspofungin, and anidulafungin against Candida albicans and Candida parapsilosis biofilms were evaluated. In contrast to planktonic cells, the MICs for voriconazole and posaconazole for the biofilms of the two species were high (>or=256 and >64 mg/liter, respectively) but relatively low for the echinocandins caspofungin and anidulafungin (相似文献   

Molecular characterization of Italian Candida parapsilosis isolates reveals the cryptic presence of the newly described species Candida orthopsilosis in blood cultures from newborns

The authors report the molecular characterization of Candida parapsilosis isolates recovered from the blood and venous central catheter tips of patients admitted to different care units of the Polyclinic Hospital, University of Messina, Italy. Among 97 presumed C. parapsilosis isolates examined, 94 were identified as C. parapsilosis sensu stricto and the remaining 3 isolates were found to belong to the cryptic species Candida orthopsilosis which was recovered only from blood cultures of neonates (<30 days old) born prematurely. No C. metapsilosis was found in this study. This study emphasizes the role of C. parapsilosis as an important nosocomial pathogen, and it also describes, for the first time, the occurrence of C. orthopsilosis in newborns.     

Activity of caspofungin and voriconazole against clinical isolates of Candida and other medically important yeasts by the CLSI M-44A disk diffusion method with Neo-Sensitabs tablets

In vitro activity of caspofungin and voriconazole against 184 clinical isolates of Candida and other medically important yeasts in comparison with that of fluconazole, ketoconazole, itraconazole and amphotericin B was determined by using a disk diffusion method (Neo-Sensitabs) standardized according to the recommendations of the CLSI documents M44-A and M44-S1 (same medium: Mueller-Hinton plus methylene blue; inoculum and minimal inhibitory concentration/zone breakpoints). Seventy-two percent of clinical isolates were susceptible to caspofungin, 23.6% showed an intermediate susceptibility (most of them were Candida parapsilosis) and 4.3% were resistant (values for Candida spp. were 71.2, 23.8 and 5%, respectively). For voriconazole, 96.7% of clinical isolates were susceptible and 3.3% were resistant (Candida spp.: 96 and 3.8%, respectively). Both caspofungin and voriconazole showed high activity against a wide variety of clinically important yeasts.     

Multilaboratory testing of two-drug combinations of antifungals against Candida albicans, Candida glabrata, and Candida parapsilosis

There are few multilaboratory studies of antifungal combination testing to suggest a format for use in clinical laboratories. In the present study, eight laboratories tested quality control (QC) strain Candida parapsilosis ATCC 22019 and clinical isolates Candida albicans 20533.043, C. albicans 20464.007, Candida glabrata 20205.075, and C. parapsilosis 20580.070. The clinical isolates had relatively high azole and echinocandin MICs. A modified CLSI M27-A3 protocol was used, with 96-well custom-made plates containing checkerboard pairwise combinations of amphotericin B (AMB), anidulafungin (AND), caspofungin (CSP), micafungin (MCF), posaconazole (PSC), and voriconazole (VRC). The endpoints were scored visually and on a spectrophotometer or enzyme-linked immunosorbent assay (ELISA) reader for 50% growth reduction (50% inhibitory concentration [IC(50)]). Combination IC(50)s were used to calculate summation fractional inhibitory concentration indices (FICIs) (ΣFIC) based on the Lowe additivity formula. The results revealed that the IC(50)s of all drug combinations were lower or equal to the IC(50) of individual drugs in the combination. A majority of the ΣFIC values were indifferent (ΣFIC = 0.51 to 2.0), but no antagonism was observed (ΣFIC ≥ 4). Synergistic combinations (ΣFIC ≤ 0.5) were found for AMB-PSC against C. glabrata and for AMB-AND and AMB-CSP against C. parapsilosis by both visual and spectrophotometric readings. Additional synergistic interactions were revealed by either of the two endpoints for AMB-AND, AMB-CSP, AMB-MCF, AMB-PSC, AMB-VRC, AND-PSC, CSP-MCF, and CSP-PSC. The percent agreements among participating laboratories ranged from 37.5% (lowest) for AND-CSP and POS-VOR to 87.5% (highest) for AMB-MCF and AND-CSP. Median ΣFIC values showed a wide dispersion, and interlaboratory agreements were less than 85% in most instances. Additional studies are needed to improve the interlaboratory reproducibility of antifungal combination testing.     

Emergence of a Candida krusei isolate with reduced susceptibility to caspofungin during therapy

Clinical failure associated with reduced susceptibility to caspofungin has been described in Candida albicans and C. parapsilosis. We report a case of Candida krusei infection that progressed despite caspofungin therapy. Reduced microbial susceptibility to all three echinocandins (caspofungin, anidulafungin, and micafungin) was noted but was not associated with mutations in FKS1.     

In vitro activity of three new triazoles and one echinocandin against Candida bloodstream isolates from cancer patients

The in vitro activities of voriconazole, posaconazole, ravuconazole and micafungin were compared with those of fluconazole, itraconazole, ketoconazole, flucytosine and amphotericin B against 164 candidaemia isolates recovered from cancer patients in two Canadian centres. The MIC(50) results for ravuconazole, voriconazole, posaconazole and micafungin were 0.01, 0.03, 0.12 and 0.25 mg/L, respectively. The new antifungal agents showed substantial activity against isolates demonstrating in vitro resistance to fluconazole and itraconazole. These results suggest that the newer antifungal agents possess promising activity against invasive Candida isolates, particularly against those with reduced susceptibility to fluconazole and itraconazole.     

Caspofungin at Catheter Lock Concentrations Eradicates Mature Biofilms of Candida lusitaniae and Candida guilliermondii

The antibiofilm activities of caspofungin, anidulafungin, micafungin, and liposomal amphotericin B were studied against Candida lusitaniae, Candida guilliermondii, and a Candida albicans control strain. While anidulafungin and micafungin (0.007 to 2,048 mg/liter) showed reduced activity against biofilms of both test species, caspofungin displayed concentration-dependent antibiofilm activity, reaching complete and persistent eradication at concentrations achievable during lock therapy (512 to 2,048 mg/liter, P < 0.05). Although liposomal amphotericin B strongly inhibited mature biofilms, it possessed lower antibiofilm activity than caspofungin (P < 0.05).     

In vitro susceptibilities of bloodstream isolates of Candida species to six antifungal agents: results from a population-based active surveillance programme, Barcelona, Spain, 2002-2003

OBJECTIVES: The antifungal drug susceptibilities of 351 isolates of Candida species, obtained through active laboratory-based surveillance in the period January 2002-December 2003, were determined (Candida albicans 51%, Candida parapsilosis 23%, Candida tropicalis 10%, Candida glabrata 9%, Candida krusei 4%). METHODS: The MICs of amphotericin B, flucytosine, fluconazole, itraconazole, voriconazole and caspofungin were established by means of the broth microdilution reference procedure of the European Committee on Antibiotic Susceptibility Testing. RESULTS AND CONCLUSIONS: Amphotericin B and flucytosine were active in vitro against all strains. A total of 24 isolates (6.8%) showed decreased susceptibility to fluconazole (MIC > or = 16 mg/L) and 43 (12.3%) showed decreased susceptibility to itraconazole (MIC > or = 0.25 mg/L). Voriconazole and caspofungin were active in vitro against the majority of isolates, even those that were resistant to fluconazole.     

Anidulafungin: a new echinocandin with a novel profile

BACKGROUND: Until recently, available treatment for serious fungal infections comprised amphotericin B and azoles, which have limitations. Renal toxicity is a major concern with amphotericin B, while drug-drug interactions, hepatotoxicity, and skin rashes are the primary concerns with the azole medications. The development of the echinocandins, including caspofungin, has helped to fill the need for more efficacious antifungals that are useful across different patient populations and have a good safety profile. Anidulafungin is an echinocandin being developed to treat mucosal and invasive fungal infections. OBJECTIVE: The aim of this report was to describe the pharmacodynamic and pharmacokinetic (PK) properties of anidulafungin. METHODS: Data were identified using MEDLINE and National Library of Medicine Gateway searches for English-language literature (key words: anidulafungin, esophageal candidiasis, echinocandin, caspofungin, ravuconazole, voriconazole, posaconazole, micafungin, and fluconazole; years: 1996-2004), and from meeting abstracts of the American Society for Blood and Marrow Transplantation (Arlington Heights, Illinois), European Congress of Clinical Microbiology and Infectious Diseases (Basel, Switzerland), International Conference on Antimicrobial Agents and Chemotherapy (Washington, DC), and Infectious Diseases Society of America (Arlington, Virginia). RESULTS: Anidulafungin has potent in vitro activity against Aspergillus and Candida spp, including those resistant to either fluconazole or amphotericin B. Results of several clinical trials imply that anidulafungin is effective in treating esophageal candidiasis (EC), candidemia, and invasive candidiasis (IC). In a Phase III, randomized, blinded clinical trial evaluating anidulafungin (50 mg/d) versus fluconazole (100 mg/d) for the treatment of EC, 97.2% and 98.9% of patients who received anidulafungin and fluconazole, respectively, showed evidence of cure or improvement (treatment difference, -1.6%; 95% CI, -4.1 to 0.8). In a Phase II study of candidasis and candidemia, anidulafungin showed success rates of 72%, 85%, and 83% in patients receiving the drug at dosages of 50, 75, or 100 mg/d, respectively. Studies evaluating the concomitant use of anidulafungin and either amphotericin, voriconazole, or cyclosporine did not show clinically significant drug-drug interactions or altered adverse-event (AE) profiles (P < 0.05). A population PK analysis showed no significant effect of age, race, concomitant medications, or renal or hepatic insufficiency on the PK properties of anidulafungin (P < 0.05). CONCLUSIONS: Anidulafungin may offer a new option to treat serious fungal infections, such as EC, azole-refractory EC, candidemia, and IC. In addition, anidulafungin has been associated with no clinically significant drug-drug interactions and few treatment-related AEs. Anidulafungin may offer a new option in the management of serious and difficult-to-treat invasive fungal infections.     

Multilaboratory Testing of Antifungal Drug Combinations against Candida Species and Aspergillus fumigatus: Utility of 100 Percent Inhibition as the Endpoint

Four laboratories tested three isolates of Candida species and two isolates of Aspergillus fumigatus using 96-well plates containing combinations of amphotericin B, anidulafungin, caspofungin, micafungin, fluconazole, itraconazole, posaconazole, and voriconazole. The majority of summation fractional inhibitory concentration indices (ΣFICI) based on the Lowe additivity formula suggested indifferent drug interactions (ΣFICI > 0.5 and ≤4.0) and no instance of drug antagonism (ΣFICI > 4.0). The intra- and interlaboratory agreement rates were superior when MIC₁₀₀ readings were used as endpoints (at a 99% confidence interval [CI]).     

In Vitro Activities of Nine Antifungal Drugs and Their Combinations against Phialophora verrucosa

The in vitro activities of nine antifungal drugs and their combinations against 31 clinical and 15 environmental Phialophora verrucosa strains were tested. The MIC₉₀/90% minimum effective concentration (MIC/MEC₉₀) values (μg/ml) across all strains were as follows: for terbinafine, 0.25; for posaconazole, 0.5; for voriconazole, 1; for itraconazole, 2; for amphotericin B, 4; for caspofungin and micafungin, 16; and for fluconazole and flucytosine, 64. The highest synergy was shown by the combination of itraconazole plus caspofungin (with synergy against 100% of the 31 clinical strains), followed by amphotericin B plus flucytosine (45.2%) and itraconazole plus terbinafine or micafungin (25.8% or 12.9%, respectively).     

Paradoxical effect of Echinocandins across Candida species in vitro: evidence for echinocandin-specific and candida species-related differences

Paradoxical growth of some Candida isolates occurs at concentrations above the MIC for echinocandins. In 60 Candida bloodstream isolates from cancer patients (20 C. albicans isolates and 10 isolates each of C. parapsilosis, C. tropicalis, C. krusei, and C. glabrata), paradoxical growth was more frequent with caspofungin than micafungin or anidulafungin, was unrelated to MIC, and was strikingly absent in C. glabrata isolates.     

In vitro susceptibilities of invasive isolates of Candida species: rapid increase in rates of fluconazole susceptible-dose dependent Candida glabrata isolates

Voriconazole, posaconazole, caspofungin, micafungin, and anidulafungin demonstrated potent in vitro activities against 286 invasive Candida isolates. Analysis of the fluconazole susceptibilities of 204 bloodstream Candida glabrata isolates revealed a rapid shift from susceptible (64% in 1999 to 2001 to 19% in 2007) to susceptible-dose dependent (27% in 1999 to 2001 and 75% in 2007).