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.     

Detection of fluconazole-resistant isolates of Candida glabrata by using an agar screen assay

The ability of a fluconazole-containing agar screen assay to accurately detect isolates of Candida glabrata resistant to the azole antifungal agent fluconazole was evaluated on a collection of 100 clinical isolates of this organism. Results were correlated with the MIC of fluconazole for these isolates and compared with the results of a previously published disk diffusion-based fluconazole resistance screening test. Agar screen assay results were in categorical agreement with MIC-based determinations for 97% (97/100) of the isolates tested. This correlation was higher than that obtained with the disk diffusion technique, which categorized only 87% (87/100) of isolates correctly, and suggests that the agar screening approach can effectively expedite fluconazole susceptibility testing of C. glabrata isolates.     

Voriconazole and fluconazole susceptibility of Candida isolates

An adapted NCCLS M27-A method was used to evaluate the activity of voriconazole (VRC) and fluconazole (FLC) against 295 Candida isolates collected from 189 patients (including isolates from deep sites). Isolates included 186 C. albicans, 54 C. glabrata, 27 C. tropicalis, 14 C. parapsilosis, 6 C. krusei, 6 C. lusitaniae, 1 C. lypolytica and 1 C. sake. Forty-two isolates had reduced susceptibility to FLC (MIC >8 mg/L); 83.3% of these had VRC MICs < or =2 mg/L (9 of 11 C. albicans, 18 of 19 C glabrata, 6 of 6 C. krusei, 2 of 2 C. lusitaniae and 0 of 4 C. tropicalis), including 60% of isolates collected from deep-seated infections. These results suggested that in the era of azole resistance, VRC has a promising antifungal activity for serious infections with Candida spp., including most species with low susceptibility to FLC and uncommonly isolated species.     

Antifungal susceptibilities of Candida species causing vulvovaginitis and epidemiology of recurrent cases

There are limited data regarding the antifungal susceptibility of yeast causing vulvovaginal candidiasis, since cultures are rarely performed. Susceptibility testing was performed on vaginal yeast isolates collected from January 1998 to March 2001 from 429 patients with suspected vulvovaginal candidiasis. The charts of 84 patients with multiple positive cultures were reviewed. The 593 yeast isolates were Candida albicans (n = 420), Candida glabrata (n = 112), Candida parapsilosis (n = 30), Candida krusei (n = 12), Saccharomyces cerevisiae ( n = 9), Candida tropicalis (n = 8), Candida lusitaniae (n = 1), and Trichosporon sp. (n = 1). Multiple species suggesting mixed infection were isolated from 27 cultures. Resistance to fluconazole and flucytosine was observed infrequently (3.7% and 3.0%); 16.2% of isolates were resistant to itraconazole (MIC > or = 1 microg/ml). The four imidazoles (econazole, clotrimazole, miconazole, and ketoconazole) were active: 94.3 to 98.5% were susceptible at < or =1 microg/ml. Among different species, elevated fluconazole MICs (> or = 16 microg/ml) were only observed in C. glabrata (15.2% resistant [R], 51.8% susceptible-dose dependent [S-DD]), C. parapsilosis (3.3% S-DD), S. cerevisiae (11.1% S-DD), and C. krusei (50% S-DD, 41.7% R, considered intrinsically fluconazole resistant). Resistance to itraconazole was observed among C. glabrata (74.1%), C. krusei (58.3%), S. cerevisiae (55.6%), and C. parapsilosis (3.4%). Among 84 patients with recurrent episodes, non-albicans species were more common (42% versus 20%). A > or = 4-fold rise in fluconazole MIC was observed in only one patient with C. parapsilosis. These results support the use of azoles for empirical therapy of uncomplicated candidal vulvovaginitis. Recurrent episodes are more often caused by non-albicans species, for which azole agents are less likely to be effective.     

Identification and expression of multidrug resistance-related ABC transporter genes in Candida krusei.

Infections with Candida krusei have increased in recent years as a consequence of its intrinsic resistance to fluconazole, an antifungal azole widely used in immunocompromised individuals to suppress infections due to azole-susceptible C. albicans. One established mechanism for azole resistance is drug efflux by ATP binding cassette (ABC) transporters. Since these transporters recognize structurally diverse drugs, their overexpression can lead to multidrug resistance (MDR). To identify C. krusei genes potentially involved in azole resistance, PCR was performed with primers corresponding to conserved sequences of MDR-related ABC transporters from other fungi. Two genes, ABC1 and ABC2, were identified; Southern blots suggested that both have one or two related gene copies in the C. krusei genome. ABC1 RNA was constitutively expressed at low levels in log phase cells while ABC2 RNA was undetectable. However, both genes were upregulated as cultures approached stationary phase, and this upregulation was correlated with decreased susceptibility to the lethal activity of the azole derivative miconazole. Furthermore, ABC1 was upregulated following brief treatment of C. krusei with miconazole and clotrimazole (but not other azoles), and the unrelated compounds albendazole and cycloheximide. The latter two compounds antagonized fluconazole activity versus C. krusei, supporting a role for the ABC1 transporter in azole efflux. Finally, miconazole-resistant mutants selected in vitro demonstrated increased constitutive expression of ABC1. Based on these expression data, genetic and functional characterization of the ABC1 transporter to directly test its role in C. krusei azole resistance would appear to be warranted.     

In-vitro resistance to azoles associated with mitochondrial DNA deficiency in Candida glabrata.

A commercially available disk diffusion procedure was used in a large-scale study to evaluate the susceptibility of a wide range of Candida isolates to polyenes and azoles. With almost all isolates of C. glabrata resistant colonies were present within the inhibition zones for the azole compounds fluconazole, ketoconazole and miconazole, and less frequently for isoconazole, econazole and clotrimazole. Ten randomly selected isolates were cloned by limiting dilution and the susceptibility of the resulting strains to polyenes and azoles was determined. All strains presented a similar susceptibility pattern with sensitivity to polyenes and the presence of resistant colonies for all azole compounds except tioconazole. For each strain and each antifungal agent, one of these resistant colonies was subcultured and studied for antifungal susceptibility. All these colonies showed similar properties regardless of which antifungal agent allowed their selection, with increased sensitivity to polyenes and cross-resistance to the azole compounds except tioconazole. Similar results were obtained on Shadomy's modified medium and on synthetic medium. Likewise, determination of MICs by the Etest method confirmed the resistance to fluconazole. Comparative growth studies revealed a respiratory deficiency in the mutants caused by mitochondrial DNA (mtDNA) deletions. In addition, 'petite' mutants were obtained from a wild-type strain by exposure to ethidium bromide, and these respiratory mutants were shown to be resistant to azoles. These results demonstrate the relationship between mtDNA deficiency and resistance to azoles, and provide an interesting model to study the mechanisms of action of these antifungal agents.     

Changes in karyotype and azole susceptibility of sequential bloodstream isolates from patients with Candida glabrata candidemia

We examined the changes in genotypes and azole susceptibilities among sequential bloodstream isolates of Candida glabrata during the course of fungemia and the relationship of these changes to antifungal therapy. Forty-one isolates were obtained from 15 patients (9 patients who received antifungal therapy and 6 patients who did not) over periods of up to 36 days. The isolates were analyzed using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) and tested for antifungal susceptibility to fluconazole, itraconazole, and voriconazole. PFGE typing consisted of electrophoretic karyotyping and restriction endonuclease analysis of genomic DNA by use of NotI (REAG-N). The 41 isolates yielded 23 different karyotypes and 11 different REAG-N patterns but only 3 MLST types. The sequential strains from each patient had identical or similar REAG-N patterns. However, they had two or three different karyotypes in 6 (40%) of 15 patients. The isolates from these six patients exhibited the same or similar azole susceptibilities, and five patients did not receive antifungal therapy. Development of acquired azole resistance in sequential isolates was detected for only one patient. For this patient, an isolate of the same genotype obtained after azole therapy showed three- or fourfold increases in the MICs of all three azole antifungals and exhibited increased expression of the CgCDR1 efflux pump. This study shows that karyotypic changes can develop rapidly among sequential bloodstream strains of C. glabrata from the same patient without antifungal therapy. In addition, we confirmed that C. glabrata could acquire azole resistance during the course of fungemia in association with azole therapy.     

Fluconazole and voriconazole multidisk testing of Candida species for disk test calibration and MIC estimation

Fluconazole and voriconazole MICs were determined for 114 clinical Candida isolates, including isolates of Candida albicans, Candida glabrata, Candida krusei, Candida lusitaniae, Candida parapsilosis, and Candida tropicalis. All strains were susceptible to voriconazole, and most strains were also susceptible to fluconazole, with the exception of C. glabrata and C. krusei, the latter being fully fluconazole resistant. Single-strain regression analysis (SRA) was applied to 54 strains, including American Type Culture Collection reference strains. The regression lines obtained were markedly different for the different Candida species. Using an MIC limit of susceptibility to fluconazole of < or =8 microg/ml, according to NCCLS standards, the zone breakpoint for susceptibility for the 25-microg fluconazole disk was calculated to be > or =18 mm for C. albicans and > or =22 mm for C. glabrata and C. krusei. SRA results for voriconazole were used to estimate an optimal disk content according to rational criteria. A 5-microg disk content of voriconazole gave measurable zones for a tentative resistance limit of 4 microg/ml, whereas a 2.5-microg disk gave zones at the same MIC level for only three of the species. A novel SRA modification, multidisk testing, was also applied to the two major species, C. albicans and C. glabrata, and the MIC estimates were compared with the true MICs for the isolates. There was a significant correlation between the two measurements. Our results show that disk diffusion methods might be useful for azole testing of Candida isolates. The method can be calibrated using SRA. Multidisk testing gives direct estimations of the MICs for the isolates.     

Species distribution and fluconazole susceptibility of Candida clinical isolates in a medical center in 2002.

Fluconazole disk-diffusion susceptibility was evaluated in 230 blood isolates and 344 non-blood clinical isolates of Candida spp. collected in 2002 at National Taiwan University Hospital. Up to 93.5% of blood isolates were susceptible to fluconazole, 3% were susceptible dose-dependent, and 3.5% were resistant. The minimum inhibitory concentrations at which 50% of tested isolates were inhibited (MIC50) of fluconazole against Candida blood isolates were highest for Candida glabrata (5 microg/mL), followed by Candida tropicalis (2.4 microg/mL), Candida albicans (2.4 microg/mL), and Candida parapsilosis (0.41 microg/mL). C. glabrata had less fluconazole-susceptible strains (76.7%) than C. albicans (98.2%), C. tropicalis (98%) and C. parapsilosis (93.8%) [p<0.05]. The proportions of fluconazole resistance in the non-blood isolates of C. albicans, C. glabrata and C. parapsilosis were similar to those of the blood isolates. However, the proportions of fluconazole resistance in the non-blood isolates of C. tropicalis surpassed those of the blood isolates (14.7% vs 2%, p<0.05). Comparison of species distribution of Candida blood isolates obtained in 2002 to those in 1981-2000 demonstrated that C. albicans remained the leading pathogen, and the proportion of C. albicans in blood isolates was lowest in 1996 (38%) and did not change significantly thereafter. However, the proportion of C. tropicalis increased from 14% during 1981-1993 to 22-23% during 1996-2002. Overall, the MIC50, MIC90 and the proportion of Candida blood isolates with fluconazole resistance remained stable during 1994-2002.     

Prevalence and antifungal susceptibility of 442 Candida isolates from blood and other normally sterile sites: results of a 2-year (1996 to 1998) multicenter surveillance study in Quebec, Canada

During a 2-year surveillance program (1996 to 1998) in Quebec, Canada, 442 strains of Candida species were isolated from 415 patients in 51 hospitals. The distribution of species was as follows: Candida albicans, 54%; C. glabrata, 15%; C. parapsilosis, 12%; C. tropicalis, 9%; C. lusitaniae, 3%; C. krusei, 3%; and Candida spp., 3%. These data, compared to those of a 1985 survey, indicate variations in species distribution, with the proportions of C. glabrata and C. parapsilosis increasing by 9 and 4%, respectively, and those of C. albicans and C. tropicalis decreasing by 10 and 7%, respectively. However, these differences are statistically significant for C. glabrata and C. tropicalis only. MICs of amphotericin B were > or =4 microg/ml for 3% of isolates, all of which were non-C. albicans species. Three percent of C. albicans isolates were resistant to flucytosine (> or =32 microg/ml). Resistance to itraconazole (> or =1 microg/ml) and fluconazole (> or =64 microg/ml) was observed, respectively, in 1 and 1% of C. albicans, 14 and 9% of C. glabrata, 5 and 0% of C. tropicalis, and 0% of C. parapsilosis and C. lusitaniae isolates. Clinical data were obtained for 343 patients. The overall crude mortality rate was 38%, reflecting the multiple serious underlying illnesses found in these patients. Bloodstream infections were documented for 249 patients (73%). Overall, systemic triazoles had been administered to 10% of patients before the onset of candidiasis. The frequency of isolation of non-C. albicans species was significantly higher in this group of patients. Overall, only two C. albicans isolates were found to be resistant to fluconazole. These were obtained from an AIDS patient and a leukemia patient, both of whom had a history of previous exposure to fluconazole. At present, it appears that resistance to fluconazole in Quebec is rare and is restricted to patients with prior prolonged azole treatment.     

Species distribution and susceptibility to azole antifungals of Candida bloodstream isolates from eight university hospitals in Korea

PURPOSE: The incidence of Candida bloodstream infections (BSI) has increased over the past two decades. The rank order of occurrence and the susceptibility to antifungals of the various Candida species causing BSI are important factors driving the establishment of empirical treatment protocols; however, very limited multi-institutional data are available on Candida bloodstream isolates in Korea. MATERIALS AND METHODS: We investigated the susceptibility to azole antifungals and species distribution of 143 Candida bloodstream isolates recovered from eight university hospitals over a six-month period. Minimal inhibitory concentrations (MICs) of fluconazole, itraconazole, and voriconazole for each isolate were determined by the broth microdilution method of the Clinical and Laboratory Standards Institute (CLSI). RESULTS: The Candida species recovered most frequently from the blood cultures was C. albicans (49%), followed by C. parapsilosis (22%), C. tropicalis (14%), and C. glabrata (11%). The MIC ranges for the Candida isolates were 0.125 to 64 microg/mL for fluconazole, 0.03 to 2 microg/mL for itraconazole, and 0.03 to 1 microg/mL for voriconazole. Overall, resistance to fluconazole was found in only 2% of the Candida isolates (3/143), while the dose-dependent susceptibility was found in 6% (8/143). The resistance and dose-dependent susceptibility of itraconazole were found in 4% (6/143) and 14% (20/143) of the isolates, respectively. All bloodstream isolates were susceptible to voriconazole (MIC, < or = 1 microg/mL). CONCLUSION: Our findings show that C. albicans is the most common cause of Candida-related BSI, followed by C. parapsilosis, and that the rates of resistance to azole antifungals are still low among bloodstream isolates in Korea.     

Triazole cross-resistance among Candida spp.: case report, occurrence among bloodstream isolates, and implications for antifungal therapy

Candida spp. are common causes of bloodstream infections among hospitalized patients. Fluconazole (FLC) remains a first-line therapy for candidemia; and voriconazole (VRC), an expanded-spectrum triazole, was recently approved for the treatment of candidemia in nonneutropenic patients. In vitro studies have suggested that VRC has potent activity against Candida spp. with reduced susceptibilities to FLC. We present a case report of invasive candidiasis and candidemia due to a Candida glabrata isolate that developed resistance to all currently available triazole antifungals after a course of FLC treatment. This case prompted us to determine the frequency of cross-resistance among bloodstream Candida isolates collected during a recent 12-month period at a large, academic medical center. FLC MICs were determined for 125 of 153 isolates (81.7%). Thirty of 125 isolates (24%) were resistant or showed reduced susceptibilites to FLC (MICs >/= 16 microg/ml). When 28 of these 30 isolates were tested for their VRC susceptibilities, 9 (32%) had MICs that were >/=2 microg/ml. Five of these nine isolates were C. glabrata, two isolates were Candida tropicalis, one isolate was Candida albicans, and one isolate was Candida parapsilosis. All five Candida krusei isolates tested had VRC MICs 相似文献   

Azole resistance of Candida glabrata in a case of recurrent fungemia

We describe a case of recurrent Candida glabrata fungemia that became unresponsive to fluconazole treatment. Posttreatment isolates from blood and vaginal cultures of the immunocompetent patient were azole resistant and exhibited upregulated expression of CgCDR1/CgCDR2 efflux pumps compared to the original isolates. Amphotericin B therapy eradicated the infection.     

In-vivo selection of an azole-resistant petite mutant of Candida glabrata

Two isolates of Candida glabrata from the same stool sample from a bone marrow transplant recipient treated with fluconazole, and designated 1084-L for large colonies on yeast extract-peptone-dextrose-agar and 1084-S for small colonies, were analysed. In-vitro susceptibility tests with a commercially available disk diffusion procedure showed that isolate 1084-L had a susceptibility pattern typical of wild-type strains of C. glabrata with sensitivity to polyenes and the presence of resistant colonies randomly distributed within the inhibition zones for all azole compounds except tioconazole. In contrast, isolate 1084-S, which was found by pulsed-field gel electrophoresis and random amplification of polymorphic DNA to be genetically closely related to isolate 1084-L, exhibited cross-resistance to the azole compounds except tioconazole. Determination of MICs by the E-test method confirmed these results, showing that isolate 1084-S had greater sensitivity to amphotericin B and complete resistance to ketoconazole and fluconazole. Growth on agar plates containing glucose or glycerol as the sole carbon source suggested that the resistant isolate had a respiratory deficiency, which was further demonstrated by flow cytometric analysis of the fluorescence of rhodamine 123-stained blastoconidia. Restriction endonuclease analysis of mitochondrial DNA (mtDNA) established the mitochondrial origin of the respiratory deficiency. However, PCR amplification of the mtDNA with primers ML1 and ML6, as well as transmission electron microscopy, suggested a partial deletion of the mtDNA analogous to that described for rho- petite mutants of Saccharomyces cerevisiae. Together, these results provided evidence that the selection of azole-resistant petite mutants of C. glabrata may occur in vivo after fluconazole administration, which might explain, therefore, clinical failure of antifungal therapy.     

Synergistic effects of tea polyphenol epigallocatechin 3-O-gallate and azole drugs against oral Candida isolates

BackgroundThe antifungal drug resistance has become an emerging problem in the management of candida infections worldwide. The objective of this study was to examine the efficacy of epigallocatechin 3-O-gallate (EGCG) alone and in combination with fluconazole/ketoconazole drugs against oral Candida isolates.MethodsMinimum inhibitory concentration (MIC) and minimum fungicidal concentrations (MFC) of EGCG against 60 oral Candida isolates and 4 ATCC strains were determined. Synergism of EGCG with azole drugs was evaluated by checkerboard micro-dilution method and calculated fractional inhibitory concentration index (FICI). Candida cells’ ultrastructure was studied by electron microscopy.ResultsMIC and MFC values of EGCG were in the range of 3.91–15.63 and 15.63–31.25 μg/mL, respectively. Minimum biofilm inhibitory concentration (MBIC) range of EGCG (62.5–125 μg/mL), was less than the ketoconazole (64–256 μg/mL) and fluconazole (128–512 μg/mL). The combination of EGCG with fluconazole/ketoconazole exhibited synergistic effects (ΣFICI ≤ 0.50). EGCG with azole drugs showed high sensitivity against the tested isolates in growth curve assays. Against the biofilm, the susceptibility of fluconazole/ketoconazole significantly increased (3 to 5 fold), after combination with EGCG (MBIC/4) (P ≤ 0.001). Electron microscopy of EGCG treated cells showed deformation of cell structure, ruptured cell wall and release of intracellular content. In molecular docking experiments, a strong interaction was observed between EGCG and fungal cell membrane molecule ergosterol.ConclusionWe conclude that EGCG synergistically enhanced the antifungal potential of azole drugs. The synergistic potential of EGCG might be helpful in preventing the development of drug resistance, in lowering the drug dosage, and thus minimizing adverse effects.     

Variations in fluconazole susceptibility and electrophoretic karyotype among oral isolates of Candida albicans from patients with AIDS and oral candidiasis.

DNA subtyping by pulsed-field gel electrophoresis and in vitro susceptibility testing were used to study strain variation and fluconazole resistance in Candida albicans isolates from patients with AIDS undergoing azole (fluconazole and clotrimazole) therapy for oropharyngeal candidiasis. A total of 29 patients suffered 71 episodes of oropharyngeal candidiasis. Overall, 121 isolates of C. albicans recovered throughout the course of treatment of each infection were available for further characterization. DNA subtyping revealed a total of 61 different DNA subtypes. In vitro susceptibility testing of the 121 isolates by using proposed standard methods of the National Committee for Clinical Laboratory Standards revealed MICs of fluconazole ranging from < or = 0.125 to > 64 micrograms/ml. The MIC for 50% of isolates tested was 0.25 microgram/ml, and the MIC for 90% of isolates tested was 8.0 micrograms/ml. MICs were > or = 64 micrograms/ml for only 7.4% of the isolates tested. The majority (62%) of the patients with oropharyngeal candidiasis and undergoing azole therapy were infected or colonized with more than one DNA subtype, and the introduction or selection of strains with a more resistant DNA subtype during the course of fluconazole therapy was not uncommon. With one exception, this did not appear to have an adverse effect on clinical outcome. In contrast, for patients with AIDS and oropharyngeal candidiasis infected with a single DNA subtype of C. albicans, an increase in fluconazole MICs for the infecting strain was rarely demonstrated over the course of therapy.     

Multiple patterns of resistance to fluconazole in Candida glabrata isolates from a patient with oropharyngeal candidiasis receiving head and neck radiation

Candida glabrata has emerged in recent years as a significant cause of systemic fungal infection. We have previously reported on the first three patients receiving radiation for head and neck cancer to develop oropharyngeal candidiasis due to C. glabrata. The goal of this study was to track the development of increased fluconazole resistance in C. glabrata isolates and to evaluate previously described genetic mechanisms associated with this resistance from one of these three patients. The patient was a 52-year-old man with squamous cell carcinoma treated with radiation. At week 7 of his radiation, he developed oropharyngeal candidiasis, which was treated with 200 mg of fluconazole daily for 2 weeks. Serial cultures from this and three subsequent time points yielded C. glabrata. Isolates from these cultures were subjected to antifungal susceptibility testing, DNA karyotyping, and evaluation of the expression of genes previously associated with C. glabrata resistance to fluconazole, CgCDR1, CgCDR2, and CgERG11. Two strains (A and B) of C. glabrata were identified and found to display different patterns of resistance development and gene expression. Strain A developed resistance over a 2-week period and showed no overexpression of these genes. In contrast, strain B first showed resistance 6 weeks after fluconazole therapy was discontinued but showed overexpression of all three genes. In conclusion, development of resistance to fluconazole by C. glabrata is a highly varied process involving multiple molecular mechanisms.     

Antifungal susceptibility of 50 Candida isolates from invasive mycoses in Chile.

We determined the antifungal susceptibility of 50 Candida isolates from invasive mycoses in intensive care unit patients in Chile. Candida albicans (27 isolates) and C. parapsilosis (12 isolates) were the most common etiologic species. Candida glabrata (five isolates) was isolated only from children. Our data are consistent with those of recent Brazilian and Argentinean studies but differ from those of some US, Canadian and Norwegian studies, in which the relatively azole-resistant C. glabrata was the predominant non-C. albicans species seen. All isolates in this study were susceptible to amphotericin B. Itraconazole and fluconazole resistance were observed in 6 and 4% of the isolates, respectively.     

In vitro activity of ibrexafungerp and comparators against Candida albicans genotypes from vaginal samples and blood cultures

ObjectivesEmergence of azole resistance may contribute to recurrences of vulvovaginal candidiasis. Thus, new drugs are needed to improve the therapeutic options. We studied the in vitro activity of ibrexafungerp and comparators against Candida albicans isolates from vaginal samples and blood cultures. Furthermore, isolates were genotyped to study compartmentalization of genotypes and the relationship between genotype and antifungal susceptibility.MethodsCandida albicans unique patient isolates (n = 144) from patients with clinical suspicion of vulvovaginal candidiasis (n = 72 isolates) and from patients with candidaemia (n = 72) were studied. Antifungal susceptibility to amphotericin B, fluconazole, voriconazole, posaconazole, isavuconazole, clotrimazole, miconazole, micafungin, anidulafungin and ibrexafungerp was tested (EUCAST 7.3.2). Mutations in the erg11 gene were analysed and isolates genotyped.ResultsIbrexafungerp showed high activity (MICs from 0.03 mg/L to 0.25 mg/L) against the isolates, including those with reduced azole susceptibility, and regardless of their clinical source. Fluconazole resistance rate was 7% (n = 5/72) and 1.4% (n = 1/72) in vaginal and blood isolates, respectively. Some amino acid substitutions in the Erg11 protein were observed exclusively in phenotypically fluconazole non-wild type. Population structure analysis suggested two genotype populations, one mostly involving isolates from blood samples (66.3%) and the mostly from vaginal samples (69.8%). The latter group hosted all fluconazole non-wild-type isolates.DiscussionIbrexafungerp shows good in vitro activity against Candida albicans from vaginal samples including phenotypically fluconazole non-wild-type isolates. Furthermore, we found a certain population structure where some genotypes show reduced susceptibility to fluconazole.     

Activities of micafungin against 315 invasive clinical isolates of fluconazole-resistant Candida spp

Micafungin is a new echinocandin exhibiting broad-spectrum activity against Candida spp. The activity of the echinocandins against Candida species known to express intrinsic or acquired resistance to fluconazole is of interest. We determined the MICs of micafungin and caspofungin against 315 invasive clinical (bloodstream and other sterile-site) isolates of fluconazole-resistant Candida species obtained from geographically diverse medical centers between 2001 and 2004. MICs were determined using broth microdilution according to the CLSI reference method M27-A2. RPMI 1640 was used as the test medium, and we used the MIC endpoint of prominent growth reduction at 24 h. Among the 315 fluconazole-resistant Candida isolates, 146 (46%) were C. krusei, 110 (35%) were C. glabrata, 41 (13%) were C. albicans, and 18 (6%) were less frequently isolated species. Micafungin had good in vitro activity against all fluconazole-resistant Candida spp. tested; the MICs at which 50% (MIC(50)) and 90% (MIC(90)) of isolates were inhibited were 0.03 microg/ml and 0.06 microg/ml, respectively. All the fluconazole-resistant Candida spp. were inhibited at a micafungin MIC that was 相似文献