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Candida aurishas demonstrated the ability to colonize the skin of hospitalized patients, possibly contributing to nosocomial spread. The objective of this study was to determine whether two novel transdermal agents could clear skin colonization established by C. auris.

ABSTRACTME1111 is a novel small molecule antifungal agent under development for the topical treatment of onychomycosis. Standardization of the susceptibility testing method for this candidate antifungal is needed. Toward this end, 8 independent laboratories determined the interlaboratory reproducibility of ME1111 susceptibility testing. In addition, we subsequently identified 2 strains as quality control (QC) isolates for the method. In the reproducibility study, 5 blinded clinical strains each of Trichophyton rubrum, Trichophyton mentagrophytes, and Epidermophyton floccosumwere tested, while the QC study tested 6 blinded T. rubrumor T. mentagrophytesATCC strains. Testing was performed in frozen microtiter panels according to the Clinical and Laboratory Standards Institute (CLSI) M38-A2 methodology. In the reproducibility study, 9 of 15 clinical strains showed interlaboratory agreement of >90% at the 80% inhibition endpoint, with a range of agreement of 76.2% to 100%. In the QC study, 4 of the 6 ATCC strains showed interlaboratory agreement of >90%. ME1111 demonstrated excellent interlaboratory agreement when tested against dermatophytes. Based on this data, the CLSI Subcommittee on Antifungal Susceptibility Tests approved the susceptibility testing of ME1111 against dermatophytes according to M38-A2 methodology, which stipulates RPMI 1640 as the test medium, an inoculum size of 1 to 3 × 103CFU/ml, and an incubation time and temperature of 96 h at 35°C. The MIC endpoint should be 80% inhibition compared with the growth control. T. rubrumATCC MYA-4438 and T. mentagrophytesATCC 28185 were selected as QC isolates, with an acceptable range of 0.12 to 1 µg/ml for the two strains.

ABSTRACTThe CLSI epidemiological cutoff values (ECVs) of antifungal agents are available for various Candidaspp., Aspergillusspp., and the Mucorales. However, those categorical endpoints have not been established for Fusariumspp., mostly due to the difficulties associated with collecting sufficient CLSI MICs for clinical isolates identified according to the currently recommended molecular DNA-PCR-based identification methodologies. CLSI MIC distributions were established for 53 Fusarium dimerumspecies complex (SC), 10 F. fujikuroi, 82 F. proliferatum, 20 F. incarnatum-F. equisetiSC, 226 F. oxysporumSC, 608 F. solaniSC, and 151 F. verticillioidesisolates originating in 17 laboratories (in Argentina, Australia, Brazil, Canada, Europe, Mexico, and the United States). According to the CLSI guidelines for ECV setting, ECVs encompassing ≥97.5% of pooled statistically modeled MIC distributions were as follows: for amphotericin B, 4 μg/ml (F. verticillioides) and 8 μg/ml (F. oxysporumSC and F. solaniSC); for posaconazole, 2 μg/ml (F. verticillioides), 8 μg/ml (F. oxysporumSC), and 32 μg/ml (F. solaniSC); for voriconazole, 4 μg/ml (F. verticillioides), 16 μg/ml (F. oxysporumSC), and 32 μg/ml (F. solaniSC); and for itraconazole, 32 μg/ml (F. oxysporumSC and F. solaniSC). Insufficient data precluded ECV definition for the other species. Although these ECVs could aid in detecting non-wild-type isolates with reduced susceptibility to the agents evaluated, the relationship between molecular mechanisms of resistance (gene mutations) and MICs still needs to be investigated for Fusariumspp.

ABSTRACTThe treatment of onychomycosis has improved considerably over the past several decades following the introduction of the oral antifungals terbinafine and itraconazole. However, these oral agents suffer from certain disadvantages, including drug interactions and potential liver toxicity. Thus, there is a need for new topical agents that are effective against onychomycosis. ME1111 is a novel selective inhibitor of succinate dehydrogenase (complex II) of dermatophyte species, whose small molecular weight enhances its ability to penetrate the nail plate. In this study, we determined the antifungal activity of ME1111 against dermatophyte strains, most of which are known to cause nail infections, as measured by the MIC (n= 400) and the minimum fungicidal concentration (MFC) (n= 300). Additionally, we examined the potential for resistance development in dermatophytes (n= 4) following repeated exposure to ME1111. Our data show that the MIC90of ME1111 against dermatophyte strains was 0.25 μg/ml, which was equivalent to that of the comparators amorolfine and ciclopirox (0.25 and 0.5 μg/ml, respectively). ME1111 was fungicidal at clinically achievable concentrations against dermatophytes, and its MFC90s against Trichophyton rubrumand Trichophyton mentagrophyteswere 8 μg/ml, comparable to those of ciclopirox. Furthermore, ME1111, as well as ciclopirox, did not induce resistance in 4 dermatophytes tested. Our studies show that ME1111 possesses potent antifungal activity and suggest that it has low potential for the development of resistance in dermatophytes.

ABSTRACTCurrent therapies used to treat dermatophytoses such as onychomycosis are effective but display room for improvement in efficacy, safety, and convenience of dosing. We report here that the investigational agent VT-1161 displays potent in vitroantifungal activity against dermatophytes, with MIC values in the range of ≤0.016 to 0.5 μg/ml. In pharmacokinetic studies supporting testing in a guinea pig model of dermatophytosis, VT-1161 plasma concentrations following single oral doses were dose proportional and persisted at or above the MIC values for at least 48 h, indicating potential in vivoefficacy with once-daily and possibly once-weekly dosing. Subsequently, in a guinea pig dermatophytosis model utilizing Trichophyton mentagrophytesand at oral doses of 5, 10, or 25 mg/kg of body weight once daily or 70 mg/kg once weekly, VT-1161 was statistically superior to untreated controls in fungal burden reduction (P< 0.001) and improvement in clinical scores (P< 0.001). The efficacy profile of VT-1161 was equivalent to those for doses and regimens of itraconazole and terbinafine except that VT-1161 was superior to itraconazole when each drug was dosed once weekly (P< 0.05). VT-1161 was distributed into skin and hair, with plasma and tissue concentrations in all treatment and regimen groups ranging from 0.8 to 40 μg/ml (or μg/g), at or above the MIC against the isolate used in the model (0.5 μg/ml). These data strongly support the clinical development of VT-1161 for the oral treatment of onychomycosis using either once-daily or once-weekly dosing regimens.

ABSTRACTThe development of a topical agent that would strengthen the nail, improve the natural barrier, and provide better drug penetration to the nail bed is needed. In this study, we examined the effects of a hydroxypropyl chitosan (HPCH)-based nail solution using a bovine hoof model. Following application of the nail solution, changes in the hardness of the hoof samples were measured using the Vickers method. Tensile and flexural strengths were tested by stretching or punching the samples, respectively. The ultrastructure was examined using scanning electron microscopy (SEM), and samples stained with periodic acid-Schiff (PAS) stain were used to determine the fungal penetration depth. The comparators included 40% urea and 70% isopropyl alcohol solutions. The HPCH nail solution increased hoof sample hardness in comparison to the untreated control sample (mean, 22.3 versus 19.4 Vickers pyramid number [HV]). Similarly, the HPCH solution increased the tensile strength (mean, 33.07 versus 28.42 MPa) and flexural strength (mean, 183.79 versus 181.20 MPa) compared to the untreated control. In contrast, the comparators had adverse effects on hardness and strength. SEM showed that the HPCH solution reduced the area of sample crumbling following abrasion compared to the untreated control (7,418 versus 17,843 pixels), and the PAS-stained images showed that the HPCH solution reduced penetration of the dermatophyte hyphae (e.g., penetration by Trichophyton mentagrophyteswas <25 μm at day 9 versus 275 μm in the untreated control). Unlike chemicals normally used in cosmetic treatments, repeated application of the HPCH nail solution may help prevent the establishment of new or recurring fungal nail infection.

ABSTRACTClinical breakpoints (CBPs) have not been established for the Mucoralesand any antifungal agent. In lieu of CBPs, epidemiologic cutoff values (ECVs) are proposed for amphotericin B, posaconazole, and itraconazole and four Mucoralesspecies. Wild-type (WT) MIC distributions (organisms in a species-drug combination with no detectable acquired resistance mechanisms) were defined with available pooled CLSI MICs from 14 laboratories (Argentina, Australia, Canada, Europe, India, Mexico, and the United States) as follows: 10 Apophysomyces variabilis, 32 Cunninghamella bertholletiae, 136 Lichtheimia corymbifera, 10 Mucor indicus, 123 M. circinelloides, 19 M. ramosissimus, 349 Rhizopus arrhizus, 146 R. microsporus, 33 Rhizomucor pusillus, and 36 Syncephalastrum racemosumisolates. CLSI broth microdilution MICs were aggregated for the analyses. ECVs comprising ≥95% and ≥97.5% of the modeled populations were as follows: amphotericin B ECVs for L. corymbiferawere 1 and 2 μg/ml, those for M. circinelloideswere 1 and 2 μg/ml, those for R. arrhizuswere 2 and 4 μg/ml, and those for R. microsporuswere 2 and 2 μg/ml, respectively; posaconazole ECVs for L. corymbiferawere 1 and 2, those for M. circinelloideswere 4 and 4, those for R. arrhizuswere 1 and 2, and those for R. microsporuswere 1 and 2, respectively; both itraconazole ECVs for R. arrhizuswere 2 μg/ml. ECVs may aid in detecting emerging resistance or isolates with reduced susceptibility (non-WT MICs) to the agents evaluated.

ABSTRACTEsophageal candidiasis is a frequent cause of morbidity in immunocompromised patients. Isavuconazole is a novel, broad-spectrum antifungal developed for the treatment of opportunistic fungal infections. This phase 2 trial compared the efficacy and safety of three oral dosing regimens of isavuconazole with an oral fluconazole regimen in the primary treatment of uncomplicated esophageal candidiasis. The isavuconazole regimens were as follows: 200 mg on day 1 and then 50 mg once daily (arm A), 400 mg on day 1 and then 400 mg once-weekly (arm B), and 400 mg on day 1 and then 100 mg once daily (arm C). Patients in arm D received fluconazole at 200 mg on day 1 and then 100 mg once daily. The minimum treatment duration was 14 days. The primary endpoint was the rate of endoscopically confirmed clinical response at end of therapy. Safety and tolerability were also assessed. Efficacy was evaluated in 153 of 160 enrolled patients. Overall, 146 (95.4%) achieved endoscopically confirmed clinical success. Each of the isavuconazole regimens was shown to be not inferior to fluconazole, i.e., arm A versus D, −0.5% (95% confidence interval [CI] −10.0 to 9.4), arm B versus D, 3.5% (95% CI, −5.6 to 12.7), and arm C versus D, −0.2% (95% CI, −9.8 to 9.4). The frequency of adverse events was similar in arm A (n= 22; 55%), arm B (n= 18; 45%), and arm D (n= 22; 58%), but higher in arm C (n= 29; 71%). In summary, efficacy and safety of once-daily and once-weekly isavuconazole were comparable with once-daily fluconazole in the primary treatment of uncomplicated esophageal candidiasis.

ABSTRACTThe incidence of superficial dermatophytoses is high in developed countries, and there remains a need for effective topical antifungals. In this study, we evaluated the in vitroantifungal activity of naftifine hydrochloride, the active ingredient in naftifine hydrochloride cream and gel 1% and 2%, against dermatophytes. The MICs and minimum fungicidal concentrations (MFCs) of naftifine hydrochloride against 350 clinical strains, including Trichophyton rubrum, T. mentagrophytes, T. tonsurans, Epidermophyton floccosum, and Microsporum canis, were determined using the CLSI methodology. Subsets from this test panel were subsequently tested in a time-kill assay at 0.125×, 0.25×, 0.5×, and 1× the MFC for each isolate. CFU counts were performed over a period of 48 h of incubation. Additionally, in order to determine the potential for resistance development, six strains were subjected to 15 serial passages in concentrations higher than the MIC for each strain. MICs were determined following each passage. The MIC range against the dermatophyte isolates tested was 0.015 to 1.0 μg/ml, with naftifine hydrochloride being fungicidal against 85% of the Trichophytonspecies. The time-kill assay showed dose-dependent activity, with the greatest reduction in the numbers of CFU corresponding to the highest drug concentration. There was no increase in MIC for any strains following repeated exposure to naftifine hydrochloride. Naftifine hydrochloride demonstrated potent activity against all dermatophytes tested, and none of the isolates within this test panel demonstrated the potential for the development of resistance. Thus, future clinical studies of naftifine hydrochloride against dermatophytes may be warranted for the treatment of superficial dermatophytoses.

ABSTRACTClinical breakpoints (CBPs) and epidemiological cutoff values (ECVs) have been established for several Candidaspp. and the newer triazoles and echinocandins but are not yet available for older antifungal agents, such as amphotericin B, flucytosine, or itraconazole. We determined species-specific ECVs for amphotericin B (AMB), flucytosine (FC) and itraconazole (ITR) for eight Candidaspp. (30,221 strains) using isolates from 16 different laboratories in Brazil, Canada, Europe, and the United States, all tested by the CLSI reference microdilution method. The calculated 24- and 48-h ECVs expressed in µg/ml (and the percentages of isolates that had MICs less than or equal to the ECV) for AMB, FC, and ITR, respectively, were 2 (99.8)/2 (99.2), 0.5 (94.2)/1 (91.4), and 0.12 (95.0)/0.12 (92.9) for C. albicans; 2 (99.6)/2 (98.7), 0.5 (98.0)/0.5 (97.5), and 2 (95.2)/4 (93.5) for C. glabrata; 2 (99.7)/2 (97.3), 0.5 (98.7)/0.5 (97.8), and 05. (99.7)/0.5 (98.5) for C. parapsilosis; 2 (99.8)/2 (99.2), 0.5 (93.0)/1 (90.5), and 0.5 (97.8)/0.5 (93.9) for C. tropicalis; 2 (99.3)/4 (100.0), 32 (99.4)/32 (99.3), and 1 (99.0)/2 (100.0) for C. krusei; 2 (100.0)/4 (100.0), 0.5 (95.3)/1 (92.9), and 0.5 (95.8)/0.5 (98.1) for C. lusitaniae; -/2 (100.0), 0.5 (98.8)/0.5 (97.7), and 0.25 (97.6)/0.25 (96.9) for C. dubliniensis; and 2 (100.0)/2 (100.0), 1 (92.7)/-, and 1 (100.0)/2 (100.0) for C. guilliermondii. In the absence of species-specific CBP values, these wild-type (WT) MIC distributions and ECVs will be useful for monitoring the emergence of reduced susceptibility to these well-established antifungal agents.

ABSTRACTTDT 067 is a novel, carrier-based dosage form of terbinafine in Transfersome (1.5%) formulated for topical delivery of terbinafine to the nail, nail bed, and surrounding tissue. We examined the effects of TDT 067 and conventional terbinafine on the morphology of dermatophytes. Trichophyton rubrumhyphae were exposed to TDT 067 or terbinafine (15 mg/ml) and examined under white light, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Subungual debris from patients treated with TDT 067 in a clinical trial was also examined. Exposure of T. rubrumhyphae to TDT 067 led to rapid and extensive ultrastructural changes. Hyphal distortion was evident as early as 4 h after exposure to TDT 067. After 24 h, there was complete disruption of hyphal structure with few intact hyphae remaining. Exposure to terbinafine resulted in morphological alterations similar to those seen with TDT 067; however, the effects of TDT 067 were more extensive, whereas a portion of hyphae remained intact after 24 h of exposure to terbinafine. Lipid droplets were observed under TEM following 30 min of exposure to TDT 067, which after 24 h had filled the intracellular space. These effects were confirmed in vivoin subungual debris from patients with onychomycosis who received topical treatment with TDT 067. The Transfersome in TDT 067 may potentiate the action of terbinafine by delivering terbinafine more effectively to its site of action inside the fungus. Our in vivodata confirm that TDT 067 can enter fungus in the nail bed of patients with onychomycosis and exert its antifungal effects.

ABSTRACTAlthough clinical breakpoints have not been established for mold testing, epidemiological cutoff values (ECVs) are available for Aspergillusspp. versus the triazoles and caspofungin. Wild-type (WT) MIC distributions (organisms in a species-drug combination with no acquired resistance mechanisms) were defined in order to establish ECVs for six Aspergillusspp. and amphotericin B. Two sets (CLSI/EUCAST broth microdilution) of available MICs were evaluated: those for A. fumigatus(3,988/833), A. flavus(793/194), A. nidulans(184/69), A. niger(673/140), A. terreus(545/266), and A. versicolor(135/22). Three sets of data were analyzed: (i) CLSI data gathered in eight independent laboratories in Canada, Europe, and the United States; (ii) EUCAST data from a single laboratory; and (iii) the combined CLSI and EUCAST data. ECVs, expressed in μg/ml, that captured 95%, 97.5%, and 99% of the modeled wild-type population (CLSI and combined data) were as follows: for A. fumigatus, 2, 2, and 4; for A. flavus, 2, 4, and 4; for A. nidulans, 4, 4, and 4; for A. niger, 2, 2, and 2; for A. terreus, 4, 4, and 8; and for A. versicolor, 2, 2, and 2. Similar to the case for the triazoles and caspofungin, amphotericin B ECVs may aid in the detection of strains with acquired mechanisms of resistance to this agent.

ABSTRACTAlthough Clinical and Laboratory Standards Institute (CLSI) disk diffusion assay standard conditions are available for susceptibility testing of filamentous fungi (molds) to antifungal agents, quality control (QC) disk diffusion zone diameter ranges have not been established. This multicenter study documented the reproducibility of tests for one isolate each of five molds (Paecilomyces variotiiATCC MYA-3630, Aspergillus fumigatusATCC MYA-3626, A. flavusATCC MYA-3631, A. terreusATCC MYA-3633, and Fusarium verticillioides[moniliforme] ATCC MYA-3629) and Candida kruseiATCC 6258 by the CLSI disk diffusion method (M51-A document). The zone diameter ranges for selected QC isolates were as follows: P. variotiiATCC MYA-3630, amphotericin B (15 to 24 mm), itraconazole (20 to 31 mm), and posaconazole (33 to 43 mm); A. fumigatusATCC MYA-3626, amphotericin B (18 to 25 mm), itraconazole (11 to 21 mm), posaconazole (28 to 35 mm), and voriconazole (25 to 33 mm); and C. krusei, amphotericin B (18 to 27 mm), itraconazole (18 to 26 mm), posaconazole (28 to 38 mm), and voriconazole (29 to 39 mm). Due to low testing reproducibility, zone diameter ranges were not proposed for the other three molds.

ABSTRACTThe treatment of dermatophytoses, including onychomycosis, has come a long way over the past few decades with the introduction of oral antifungals (e.g., terbinafine and itraconazole). However, with these advancements in oral therapies come several undesirable effects, such as kidney and liver toxicity, along with drug-drug interactions. Consequently, there is a need for new topical agents that are effective against dermatophytosis. ME1111 is a topical antifungal under development. In this study, the in vivoefficacy of ME1111 was compared to that of ciclopirox in the topical treatment of dermatophytosis caused by Trichophyton mentagrophytesusing a guinea pig model. Animals were treated with the topical antifungals starting at 3 days postinfection, with each agent being applied once daily for seven consecutive days. After the treatment period, the clinical and mycological efficacies were evaluated. The data showed that both antifungals demonstrated significant clinical and mycological efficacies; however, ME1111 showed clinical efficacy superior to that of ciclopirox (46.9% and 25.0%, respectively, with a Pvalue of <0.001). The potent efficacy of ME1111 could be attributed to its properties, such as low keratin binding.

ABSTRACTAntifungal susceptibility testing of Aspergillusspecies has been standardized by both the Clinical and Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST). Recent studies suggest the emergence of strains of Aspergillus fumigatuswith acquired resistance to azoles. The mechanisms of resistance involve mutations in the cyp51A(sterol demethylase) gene, and patterns of azole cross-resistance have been linked to specific mutations. Studies using the EUCAST broth microdilution (BMD) method have defined wild-type (WT) MIC distributions, epidemiological cutoff values (ECVs), and cross-resistance among the azoles. We tested a collection of 637 clinical isolates of A. fumigatusfor which itraconazole MICs were =2 µg/ml against posaconazole and voriconazole using the CLSI BMD method. An ECV of =1 µg/ml encompassed the WT population of A. fumigatusfor itraconazole and voriconazole, whereas an ECV of =0.25 µg/ml was established for posaconazole. Our results demonstrate that the WT distribution and ECVs for A. fumigatusand the mold-active triazoles were the same when determined by the CLSI or the EUCAST BMD method. A collection of 43 isolates for which itraconazole MICs fell outside of the ECV were used to assess cross-resistance. Cross-resistance between itraconazole and posaconazole was seen for 53.5% of the isolates, whereas cross-resistance between itraconazole and voriconazole was apparent in only 7% of the isolates. The establishment of the WT MIC distribution and ECVs for the azoles and A. fumigatuswill be useful in resistance surveillance and is an important step toward the development of clinical breakpoints.

ABSTRACTThe CLSI Antifungal Subcommittee followed the M23-A2 “blueprint” to develop interpretive MIC breakpoints for anidulafungin, caspofungin, and micafungin against Candidaspecies. MICs of =2 µg/ml for all three echinocandins encompass 98.8 to 100% of all clinical isolates of Candidaspp. without bisecting any species group and represent a concentration that is easily maintained throughout the dosing period. Data from phase III clinical trials demonstrate that the standard dosing regimens for each of these agents may be used to treat infections due to Candidaspp. for which MICs are as high as 2 µg/ml. An MIC predictive of resistance to these agents cannot be defined based on the data from clinical trials due to the paucity of isolates for which MICs exceed 2 µg/ml. The clinical data set included only three isolates from patients treated with an echinocandin (caspofungin) for which the MICs were >2 µg/ml (two C. parapsilosisisolates at 4 µg/ml and one C. rugosaisolate at 8 µg/ml). Based on these data, the CLSI subcommittee has decided to recommend a “susceptible only” breakpoint MIC of =2 µg/ml due to the lack of echinocandin resistance in the population of Candidaisolates thus far. Isolates for which MICs exceed 2 µg/ml should be designated “nonsusceptible” (NS). For strains yielding results suggestive of an NS category, the organism identification and antimicrobial-susceptibility test results should be confirmed. Subsequently, the isolates should be submitted to a reference laboratory that will confirm the results by using a CLSI reference dilution method.

ABSTRACTA commercially prepared, dried colorimetric microdilution panel (Sensititre YeastOne Trek Diagnostic Systems, Cleveland, OH) was compared in three different laboratories with the Clinical and Laboratory Standards Institute (CLSI) reference microdilution method by testing 2 quality control strains, 25 reproducibility strains, and 404 isolates of Candidaspp. against anidulafungin, caspofungin, and micafungin. Reference MIC endpoints and YeastOne colorimetric endpoints were read after 24 h of incubation. YeastOne endpoints were determined to be the lowest concentration at which the color in the well changed from red (positive, indicating growth) to blue (negative, indicating no growth). Excellent essential agreement (within 2 dilutions) between the reference and colorimetric MICs was observed. Overall agreement was 100% for all three agents. Categorical agreement ranged from 99.3% (anidulafungin) to 100% (caspofungin, micafungin) and interlaboratory reproducibility was 99%. The YeastOne colorimetric method appears to be comparable to the CLSI reference method for testing the susceptibility of Candidaspp. to the echinocandins anidulafungin, caspofungin, and micafungin.

ABSTRACTThe Clinical and Laboratory Standards Institute (CLSI; formerly National Committee for Clinical Laboratory Standards, or NCCLS) M38-A standard for the susceptibility testing of filamentous fungi does not specifically address the testing of dermatophytes. In 2003, a multicenter study investigated the reproducibility of the microdilution method developed at the Center for Medical Mycology, Cleveland, Ohio, for testing the susceptibility of dermatophytes. Data from that study supported the introduction of this method for testing dermatophytes in the future version of the CLSI M38-A standard. In order for the method to be accepted by CLSI, appropriate quality control isolates needed to be identified. To that end, an interlaboratory study, involving the original six laboratories plus two additional sites, was conducted to evaluate potential candidates for quality control isolates. These candidate strains included five Trichophyton rubrumstrains known to have elevated MICs to terbinafine and five Trichophyton mentagrophytesstrains. Antifungal agents tested included ciclopirox, fluconazole, griseofulvin, itraconazole, posaconazole, terbinafine, and voriconazole. Based on the data generated, two quality control isolates, one T. rubrumisolate and one T. mentagrophytesisolate, were identified and submitted to the American Type Culture Collection (ATCC) for inclusion as reference strains. Ranges encompassing 95.2 to 97.9% of all data points for all seven drugs were established.

ABSTRACTDeveloping 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 Candidaspecies. The MIC distribution for voriconazole was determined using a collection of 8,702 clinical isolates. The overall MIC90was 0.25 µg/ml and 99% of the isolates were inhibited at =1 µg/ml of voriconazole. Similar results were obtained for 1,681 Candidaisolates (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 Candidaspecies: susceptible (S), =1 µg/ml; susceptible dose dependent (SDD), 2 µg/ml; and resistant (R), =4 µg/ml. The corresponding disk test breakpoints are as follows: S, =17 mm; SDD, 14 to 16 mm; and R, =13 mm.

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 µg/ml and 99% of the isolates were inhibited at ≤1 µg/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), ≤1 µg/ml; susceptible dose dependent (SDD), 2 µg/ml; and resistant (R), ≥4 µg/ml. The corresponding disk test breakpoints are as follows: S, ≥17 mm; SDD, 14 to 16 mm; and R, ≤13 mm.

ABSTRACTAlthough standard conditions are available for testing the susceptibilities of filamentous fungi to antifungal agents by the Clinical and Laboratory Standards Institute (CLSI; formerly National Committee for Clinical Laboratory Standards) broth microdilution assay, quality control (QC) MIC limits have not been established for any mold-agent combination. This multicenter (eight-center) study documented the reproducibility of tests for one isolate of Paecilomyces variotiiATCC MYA-3630 and 11 other mold isolates (three isolates of Aspergillus fumigatus; two isolates of A. terreus; one isolate each of A. flavus, A. nidulans, Fusarium moniliforme, and F. solani; and two isolates of Scedosporium apiospermum) by the CLSI reference broth microdilution method (M38-A document). Control limits (amphotericin B, 1 to 4 µg/ml; itraconazole, 0.06 to 0.5 µg/ml; posaconazole, 0.03 to 0.25 µg/ml; voriconazole, 0.015 to 0.12 µg/ml) for the selected QC P. variotiiATCC MYA-3630 were established by the analysis of replicate MIC results. Reference isolates and corresponding MIC ranges were also established for 6 of the 12 molds evaluated. MIC limits were not proposed for the other five molds tested due to low testing reproducibility for these isolates.

Background:Tinea capitis, a fungal infection of the scalp, is of increasing public health importance, and Trichophyton tonsuranshas become the primary causative agent in North America. Objectives:To determine the prevalence of dermatophyte-positive scalp cultures among elementary schoolchildren in Cleveland, Ohio, describe predisposing factors, and measure the antifungal susceptibility of isolates collected. Observations:A total of 937 children from 8 Cleveland elementary schools were cultured for the presence of dermatophytes; 122 children (13%), all of whom were African American, had dermatophyte-positive cultures of the scalp. Sixty percent of cases were asymptomatic, indicating a carrier state. Race, scaling, and the use of antidandruff shampoo were associated with increased likelihood of infection. T tonsuranswas the only organism isolated (except 1 Microsporum canisisolate). All isolates were susceptible to fluconazole, griseofulvin, itraconazole, and terbinafine. Conclusions:T tonsurans was the predominant dermatophyte isolated. Further multicenter studies are needed to confirm the predominance of dermatophyte-positive scalp cultures among African American children and to determine modifiable and preventable risk factors. (J Am Acad Dermatol 2003;48:189-93.)

SUMMARYDamp buildings often have a moldy smell or obvious mold growth; some molds are human pathogens. This has caused concern regarding health effects of moldy indoor environments and has resulted in many studies of moisture- and mold-damaged buildings. Recently, there have been reports of severe illness as a result of indoor mold exposure, particularly due to Stachybotrys chartarum. While many authors describe a direct relationship between fungal contamination and illness, close examination of the literature reveals a confusing picture. Here, we review the evidence regarding indoor mold exposure and mycotoxicosis, with an emphasis on S. chartarum. We also examine possible end-organ effects, including pulmonary, immunologic, neurologic, and oncologic disorders. We discuss the Cleveland infant idiopathic pulmonary hemorrhage reports in detail, since they provided important impetus for concerns about Stachybotrys. Some valid concerns exist regarding the relationship between indoor mold exposure and human disease. Review of the literature reveals certain fungus-disease associations in humans, including ergotism (Claviceps species), alimentary toxic aleukia (Fusarium), and liver disease (Aspergillys). While many papers suggest a similar relationship between Stachybotrys and human disease, the studies nearly uniformly suffer from significant methodological flaws, making their findings inconclusive. As a result, we have not found well-substantiated supportive evidence of serious illness due to Stachybotrys exposure in the contemporary environment. To address issues of indoor mold-related illness, there is an urgent need for studies using objective markers of illness, relevant animal models, proper epidemiologic techniques, and examination of confounding factors.

ABSTRACTBiofilms, likely the predominant mode of device-related microbial infection, exhibit resistance to antimicrobial agents. Evidence suggests that Candidabiofilms have dramatically reduced susceptibility to antifungal drugs. We examined antifungal susceptibilities of Candida albicansand Candida parapsilosisbiofilms grown on a bioprosthetic model. In addition to conventional agents, we determined if new antifungal agents (triazoles, amphotericin B lipid formulations, and echinocandins) have activities against Candidabiofilms. We also explored effects of preincubation of C. albicanscells with subinhibitory concentrations (sub-MICs) of drugs to see if they could modify subsequent biofilm formation. Finally, we used confocal scanning laser microscopy (CSLM) to image planktonic- and biofilm-exposed blastospores to examine drug effects on cell structure. Candidabiofilms were formed on silicone elastomer and quantified by tetrazolium and dry weight (DW) assays. Susceptibility testing of fluconazole, nystatin, chlorhexidine, terbenafine, amphotericin B (AMB), and the triazoles voriconazole (VRC) and ravuconazole revealed resistance in all Candidaisolates examined when grown as biofilms, compared to planktonic forms. In contrast, lipid formulations of AMB (liposomal AMB and AMB lipid complex [ABLC]) and echinocandins (caspofungin [Casp] and micafungin) showed activity against Candidabiofilms. Preincubation of C. albicanscells with sub-MIC levels of antifungals decreased the ability of cells to subsequently form biofilm (measured by DW; P< 0.0005). CSLM analysis of planktonic and biofilm-associated blastospores showed treatment with VRC, Casp, and ABLC resulted in morphological alterations, which differed with each agent. In conclusion, our data show that Candidabiofilms show unique susceptibilities to echinocandins and AMB lipid formulations.

Little is known about fungal biofilms, which may cause infection and antibiotic resistance. In this study, biofilm formation by different Candida species, particularly Candida albicans and C. parapsilosis, was evaluated by using a clinically relevant model of Candida biofilm on medical devices. Candida biofilms were allowed to form on silicone elastomer and were quantified by tetrazolium (XTT) and dry weight (DW) assays. Formed biofilm was visualized by using fluorescence microscopy and confocal scanning laser microscopy with Calcofluor White (Sigma Chemical Co., St. Louis, Mo.), concanavalin A-Alexafluor 488 (Molecular Probes, Eugene, Oreg.), and FUN-1 (Molecular Probes) dyes. Although minimal variations in biofilm production among invasive C. albicans isolates were seen, significant differences between invasive and noninvasive isolates (P < 0.001) were noted. C. albicans isolates produced more biofilm than C. parapsilosis, C. glabrata, and C. tropicalis isolates, as determined by DW assays (P was <0.001 for all comparisons) and microscopy. Interestingly, noninvasive isolates demonstrated a higher level of XTT activity than invasive isolates. On microscopy, C. albicans biofilms had a morphology different from that of other species, consisting of a basal blastospore layer with a dense overlying matrix composed of exopolysaccharides and hyphae. In contrast, C. parapsilosis biofilms had less volume than C. albicans biofilms and were comprised exclusively of clumped blastospores. Unlike planktonically grown cells, Candida biofilms rapidly (within 6 h) developed fluconazole resistance (MIC, >128 microg/ml). Importantly, XTT and FUN-1 activity showed biofilm cells to be metabolically active. In conclusion, our data show that C. albicans produces quantitatively larger and qualitatively more complex biofilms than other species, in particular, C. parapsilosis.

ABSTRACTLittle is known about fungal biofilms, which may cause infection and antibiotic resistance. In this study, biofilm formation by different Candidaspecies, particularly Candidaalbicansand C. parapsilosis, was evaluated by using a clinically relevant model of Candidabiofilm on medical devices. Candidabiofilms were allowed to form on silicone elastomer and were quantified by tetrazolium (XTT) and dry weight (DW) assays. Formed biofilm was visualized by using fluorescence microscopy and confocal scanning laser microscopy with Calcofluor White (Sigma Chemical Co., St. Louis, Mo.), concanavalin A-Alexafluor 488 (Molecular Probes, Eugene, Oreg.), and FUN-1 (Molecular Probes) dyes. Although minimal variations in biofilm production among invasive C. albicansisolates were seen, significant differences between invasive and noninvasive isolates (P< 0.001) were noted. C. albicansisolates produced more biofilm than C. parapsilosis, C. glabrata, and C. tropicalisisolates, as determined by DW assays (Pwas <0.001 for all comparisons) and microscopy. Interestingly, noninvasive isolates demonstrated a higher level of XTT activity than invasive isolates. On microscopy, C. albicansbiofilms had a morphology different from that of other species, consisting of a basal blastospore layer with a dense overlying matrix composed of exopolysaccharides and hyphae. In contrast, C. parapsilosisbiofilms had less volume than C. albicansbiofilms and were comprised exclusively of clumped blastospores. Unlike planktonically grown cells, Candidabiofilms rapidly (within 6 h) developed fluconazole resistance (MIC, >128 μg/ml). Importantly, XTT and FUN-1 activity showed biofilm cells to be metabolically active. In conclusion, our data show that C. albicansproduces quantitatively larger and qualitatively more complex biofilms than other species, in particular, C. parapsilosis.

ABSTRACTThe susceptibility of Aspergillus fumigatusto mulundocandin, an echinocandin-like compound, and other antifungal agents was assessed by the National Committee for Clinical Laboratory Standards (NCCLS) M38-P method, a 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenyl-amino)carbonyl]-2H-tetrazolium hydroxide (XTT)-based colorimetric assay, and determination of morphologic alterations by microscopy. In contrast to the NCCLS M38-P method, which does not predict the activity in vivo, the XTT-based assay showed that A. fumigatusis susceptible to mulundocandin. Thus, the XTT-based assay might be useful for determination of the susceptibilities of molds to echinocandins. Further evaluation is warranted.

ABSTRACTThe most important role of susceptibility testing is to identify potentially resistant isolates for the agent being evaluated. Standard testing guidelines recently have been proposed for antifungal susceptibility testing of filamentous fungi (molds). This collaborative (eight centers) study evaluated further newly proposed guidelines (NCCLS, proposed standard M38-P, 1998) and other testing conditions for antifungal susceptibility testing of Aspergillusspp. to itraconazole and three new triazoles, posaconazole (SCH56592), ravuconazole (BMS-207147), and voriconazole. MICs of itraconazole, posaconazole, ravuconazole, and voriconazole for 15 selected isolates of three species of Aspergillus(A. fumigatus, A. flavus, and A. terreus) with well documented in vitro, clinical, or animal data were determined in each center by using four medium formulations (standard RPMI-1640 [RPMI], RPMI with 2% dextrose, antibiotic medium 3 [M3], and M3 with 2% dextrose) and two criteria of MIC determination (complete [MIC-0s] and prominent [MIC-2s] growth inhibition) at 24, 48, and 72 h. The highest reproducibility (92 to 99%) was seen with the standard RPMI and M3 media. Moreover, the distinction between itraconazole-resistant (MICs of >8 μg/ml for clinically resistant strains) and -susceptible (MICs of 0.03 to 1 μg/ml) isolates, as well as between a voriconazole-resistant laboratory mutant and other isolates (voriconazole MICs of 2 to >8 versus 0.12 to 2 μg/ml), was more consistently evident with the standard RPMI medium and when MIC-0s were determined at 48 h. These results provide further refinement of the testing guidelines for susceptibility testing ofAspergillusspp. and warrant consideration for inclusion in the future NCCLS document M38-A.

Development of new approaches for treatment of invasive fungal infections encompasses new delivery systems for approved and investigational compounds, as well as exploiting the cell membrane, cell wall and virulence factors as putative antifungal targets. Novel delivery systems consisting of cyclodextrins, cochleates, nanoparticles/ nanospheres and long circulating ('stealth') liposomes, substantially modulate the pharmacokinetics of existing compounds, and may also be useful to enhance the delivery of antifungal agents to sites of infection. Further insights into the structureactivity relationship of the antifungal triazoles that target the biosynthesis of ergosterol in the fungal cell membrane have led to the development of highly potent broad spectrum agents, including posaconazole, ravuconazole and voriconazole. Similarly, a novel generation of cell-wall active semisynthetic echinocandin 1,3 ββ-glucan inhibitors (caspofungin, FK463, and VER-002) has entered clinical development. These agents have potent and broad-spectrum activity against Candida spp, and potentially useful activity against Aspergillus spp. and Pneumocystis carinii. The ongoing convergence of the fields of molecular pathogenesis, antifungal pharmacology and vaccine development will afford the opportunity to develop novel targets to complement the existing antifungal armamentarium.

Protection against Candida infection involves both innate and acquired immune responses, and cytokines produced by monocytes during the innate response may modify the acquired immune response by T cells. We hypothesized that Candida species which differ in pathogenicity can differentially induce production of immunoregulatory cytokines by human monocytes, which in turn modify T cells for immune responses to Candida. To test this hypothesis, we examined the effects of Candida albicans and Candida krusei on immunoregulatory cytokine production by human monocytes and gamma interferon (IFN-gamma) production by peripheral blood mononuclear cells (PBMC). Purified monocytes were incubated with live or heat-killed strains of C. albicans and C. krusei at the optimal Candida/monocyte ratio of 0.5. Cytokines in the supernatants were measured by enzyme-linked immunosorbent assay. Our data demonstrated that live C. albicans and C. krusei significantly induced interleukin-10 (IL-10), monocyte chemotactic factor 1, IL-1beta, and tumor necrosis factor alpha production by monocytes relative to unstimulated monocytes. In contrast, unlike C. krusei, pathogenic live strains of C. albicans induced no or only a minimal level of IL-12. The expression of IL-12 p40 mRNA levels by reverse transcription-PCR corroborated the IL-12 protein (p70) findings. In human PBMC, human blood monocytes were the major source of both IL-10 and IL-12 production in response to C. albicans and C. krusei. Upon activation of T cells in the presence of Candida-modified monocytes and antigen-presenting cells, IL-12 production by PBMC treated with Candida organisms correlated strongly with the level of IFN-gamma production by T cells. These results indicate that the virulence of C. albicans may be related to its ability to induce the monocytic type II cytokine IL-10, with a selective inhibition of IL-12 production, which may be responsible for the observed lack of T-cell IFN-gamma and may restrain an effective type I immune response to Candida.

Terbinafine has previously been shown to be highly vactive against dermatophytes and many other filamentous fungi. However, its activity against yeasts is controversial, with earlier reports suggesting that it has low activity, while more recent studies demonstrated that terbinafine is effective against yeasts. In this study, the in vitroactivity of terbinafine was evaluated against a broad range of fungal isolates. We examined the susceptibility of 100 yeast strains (10 species including Candida albicans, non-C. albicans, fluconazole-susceptible and-resistant candidal strains), and 184 strains of filamentous fungi and dermatophytes (29 species including Aspergillus, Fusarium, Sporothrix, Trichophyton rubrum, T. mentagrophytes, T. tonsurans, Microsporum canisand Epidermophyton floccosum), using the NCCLS M27-A microdilution methodology for yeasts and a modified M38-P methodology for moulds. The endpoint for terbinafine was defined as 80% inhibition compared with the growth control well. The mean yeast and filamentous fungi minimum inhibitory concentration values ± SEM (in mug ml-1) for terbinafine were: 6·60 ± 0·73 and 1·04 ± 0·28, respectively. In conclusion, our data suggest that terbinafine, in addition to its potent activity against dermatophytes, is considerably effective against a broad range of yeasts and filamentous fungi in vitro. Therefore, investigations concerning its antifungal activity in vivo against such organisms should be pursued.

ABSTRACTA standardized reference method for dermatophyte in vitro susceptibility testing is lacking. In a previous study, Norris et al. (H. A. Norris, B. E. Elewski, and M. A. Ghannoum, J. Am. Acad. Dermatol. 40(6, part 2):S9–S13) established the optimal medium and other growth variables. However, the earlier study did not address two issues: (i) selection of an optimal medium for conidial formation by dermatophytes and (ii) validation of the method with a large number of dermatophytes. The present study addresses these two points. To select which agar medium best supported conidial growth, representative isolates of dermatophytes were grown on different agars. Preliminary experiments showed that only oatmeal cereal agar supported the production of conidia by Trichophyton rubrum. We tested the abilities of 251 T. rubrumisolates to form conidia using three different cereal agars and potato dextrose agar. Overall, oatmeal cereal and rice agar media were comparable in their abilities to support T. rubrumconidial growth. Next, we used the oatmeal cereal agar for conidial formation along with the optimal conditions for dermatophyte susceptibility testing proposed by Norris et al. and determined the antifungal susceptibilities of 217 dermatophytes to fluconazole, griseofulvin, itraconazole, and terbinafine. Relative to the other agents tested, terbinafine possessed the highest antifungal activity against all of the dermatophytes. The mean ± standard error of the mean MICs of fluconazole, itraconazole, terbinafine, and griseofulvin were 2.07 ± 0.29, 0.13 ± 0.01, 0.002 ± 0.0003, and 0.71 ± 0.05 µg/ml, respectively. This study is the first step in the identification of optimal conditions that could be used for the standardization of the antifungal susceptibility testing method for dermatophytes. Inter- and intralaboratory agreement as well as clinical correlations need to be established.

AbstractA comparative study of conventional amphotericin B, Abelcet and AmBisome was performed using a microdilution format of the NCCLS M27-A methodology for susceptibility testing against 300 fungal isolates (152 yeasts, 148 filamentous fungi) in both RPMI-1640 and antibiotic medium #3 (AB3). The clinical isolates included Candida albicans(n=54), Candida glabrata(n=25), Candida parapsilosis(n=23), Candida krusei(n=19), Candida lusi-taniae(n=14), Cryptococcus neoformans(n=5), Candida tropicalis(n=12), Aspergillus flavus(n=34), Aspergillus fumigatus(n=46) and 68 other filamentous fungi encompassing 22 different genera. The minimal inhibitory concentrations (MIC) for all drugs were defined as the lowest concentrations in which there was no visible growth. MICs were determined after 48 h for yeasts and 72 h for filamentous fungi. The mean MICs ± standard error (μg/ml) for yeasts and filamentous fungi, respectively, were: Abelcet, 0.51 ± 0.21, 4.34± 0.61; AmBisome, 1.28± 0.24, 5.68± 0.57; amphotericin B, 0.29± 0.11, 1.12± 0.19, respectively. Overall, against both yeasts and filamentous fungi Abelcet proved to have more potent antifungal activity than AmBisome. Using AB3 as opposed to RPMI-1640 generally produced lower MIC values but did not have any effect on the order of relative activity with all of the antifungal agents tested. In conclusion, our data shows that Abelcet is more active than AmBisome against pathogenic yeast and filamentous fungi when assayed in AB3 In Vitro. Comparison of the activities of these antifungals in experimental animal models is necessary to determine whether these In Vitrofindings are correlated with in vivoefficacy.

The effects of voriconazole on the growth, morphology and lipids of Candida glabrata were studied. MIC data showed that voriconazole was up to 32- to 64-fold more active than fluconazole in its ability to inhibit various C. glabrata strains. Voriconazole inhibited the growth of C. glabrata in a dose-dependent fashion. Electron microscope examination showed that voriconazole treatment affected the external and internal morphology of C. glabrata. Treatment of C. glabrata with voriconazole inhibited ergosterol synthesis and led to accumulation of methylated sterols. In contrast, no significant difference in phospholipid composition was observed between treated and untreated cells.

ABSTRACTNational Committee for Clinical Laboratory Standards (NCCLS) standard guidelines are available for the antifungal susceptibility testing of common Candidaspp. and Cryptococcus neoformans, but NCCLS methods may not be the most efficient and convenient procedures for use in the clinical laboratory. MICs of amphotericin B, fluconazole, flucytosine, itraconazole, and ketoconazole were determined by the commercially prepared Sensititre YeastOne Colorimetric Antifungal Panel and by the NCCLS M27-A broth microdilution method for 1,176 clinical isolates of yeasts and yeast-like organisms, including Blastoschizomyces capitatus, Cryptococcusspp., 14 common and emerging species of Candida, Hansenula anomala,Rhodotorulaspp., Saccharomyces cerevisiae,Sporobolomyces salmonicolor, and Trichosporon beigelii. Colorimetric MICs of amphotericin B corresponded to the first blue well (no growth), and MICs of the other agents corresponded to the first purple or blue well. Three comparisons of MIC pairs by the two methods were evaluated to obtain percentages of agreement: 24- and 48-h MICs and 24-h colorimetric versus 48-h reference MICs. The best performance of the YeastOne panel was with 24-h MICs (92 to 100%) with the azoles and flucytosine for all the species tested, with the exception of C. albicans(87 to 90%). For amphotericin B, the best agreement between the methods was with 48-h MIC pairs (92 to 99%) for most of the species tested. The exception was for isolates ofC. neoformans(76%). These data suggest the potential value of the YeastOne panel for use in the clinical laboratory.

The effects of voriconazole on the growth, morphology and lipids of Candida glabrata were studied. MIC data showed that voriconazole was up to 32- to 64-fold more active than fluconazole in its ability to inhibit various C. glabrata strains. Voriconazole inhibited the growth of C. glabrata in a dose-dependent fashion. Electron microscope examination showed that voriconazole treatment affected the external and internal morphology of C. glabrata. Treatment of C. glabrata with voriconazole inhibited ergosterol synthesis and led to accumulation of methylated sterols. In contrast, no significant difference in phospholipid composition was observed between treated and untreated cells.

Candida albicans KTCC 89062 grown on n-alkanes showed higher levels of sterol content as compared to glucose-grown cells. Certain sterols, such as lanosterol, were significantly reduced in cells grown on n-alkanes, while others, such as ergosterol, increased in these cells. Sterol fractions declined as the chain length of the n-alkanes increased. Ergosterol supplementation of the chemically defined medium showed an increase in the uptake of dodecane (C12) by cells grown on such medium. Increase in the concentration of ergosterol supplementation resulted in an increase in C12 uptake. The uptake of C12 was not stimulated by ergosterol supplementation in the case of non-viable yeast cells.

Interactions among antineoplastic and antifungal drugs affecting the inhibition of Candida albicans growth are complex functions of the nature of the drugs used in combination, their absolute concentrations, and also their relative concentrations. Studies of drug interactions involving the use of test drugs in fixed concentration ratios can lead to inaccurate conclusions about synergism or antagonism among the drugs. A multifactorial experimental design procedure in which the concentrations of all drugs in test combinations were simultaneously varied has been used to identify and quantify drug interactions. The methods have been applied to combinations of two, three, and four drugs, including antineoplastic drugs, antifungal drugs, and combinations of antineoplastic and antifungal drugs. Results were obtained which allow predictions of effects of combinations and provide maximum effectiveness in growth inhibition with minimum levels of the test drugs.

The effects of combinations of antifungal and antineoplastic drugs on inhibition of the growth of yeasts which commonly infect cancer patients have been analyzed. It was shown that (i) inhibitory drug combinations could be selected in which all drugs were at levels far below their individual MICs; (ii) interactive effects among antineoplastic and antifungal drugs may be very large; (iii) optimum combinations of drugs for inhibition of yeast growth depended upon both the relative and absolute concentrations of the drugs in the mixture; (iv) drug combinations which were effective at low levels in inhibiting one test yeast were also generally effective against other species, but the levels of susceptibilities and, to a lesser extent, the best ratios of drugs in the test combinations varied with species; and (v) to quantitatively evaluate drug interactions, it is necessary to carefully define and control all experimental conditions, absolute and relative concentrations of drugs used, and the organisms tested.

Although it is known that Candida albicans causes endothelial cell injury, in vitro and in vivo, the mechanism by which this process occurs remains unknown. Iron is critical for the induction of injury in many types of host cells. Therefore, we investigated the role of iron in Candida-induced endothelial cell injury. We found that pretreatment of endothelial cells with the iron chelators phenanthroline and deferoxamine protected them from candidal injury, even though the organisms germinated and grew normally. Loading endothelial cells with iron reversed the cytoprotective effects of iron chelation. Moreover, chelation of endothelial cell iron significantly reduced phagocytosis of C. albicans by these cells, while candidal adherence to chelator-treated endothelial cells was slightly enhanced. Since endothelial cell phagocytosis of C. albicans is required for endothelial cell injury to occur, inhibition of phagocytosis is likely the principal mechanism of the cytoprotective effects of iron chelation. The production of toxic reactive oxygen intermediates by host cells is known to be inhibited by iron chelation. Therefore, we investigated whether treating endothelial cells with antioxidants could mimic the cytoprotective effects of iron chelation. Neither extracellular nor membrane-permeative antioxidants reduced candidal injury of endothelial cells. Furthermore, depleting endothelial cells of the endogenous antioxidant glutathione did not render them more susceptible to damage by C. albicans. These results suggest that candidal injury of endothelial cells is independent of the production of reactive oxygen intermediates and that the cytoprotective effects of iron chelation are not due to inhibition of the synthesis of these toxic intermediates.

The role of chemotherapy, X-irradiation and a combination of both on the phenomenon of adherence of yeast to buccal epithelial cells (BEC) was investigated in vitro. Growth of three Candida spp. in the presence of eight of eleven antineoplastic agents led to reduction of adherence of the isolates tested (reduction between 30% and 61% of the control value), and this effect was observed whether exponential or stationary phase Candida cells were used. Exposure of C. albicans to various doses of radiation also led to a reduction in adherence of this yeast to BEC between 31% and 53% of the control value. This reduction was shown to be dose related. Similar results were obtained when BEC were exposed to radiation, and the effect of radiation treatment was accentuated when both yeast and BEC were irradiated simultaneously. Furthermore, treating C albicans with a combination of chemotherapy and radiation led to the greatest reduction in adherence of yeast to BEC compared to when the yeast was treated with either chemotherapy or radiation alone (reduction between 63% to 74% as compared with control). The possible mechanism/s involved in reduction of adherence of yeast to BEC are discussed.

Autoclaved solutions of the fusogen Polyethylene Glycol (PEG) give reduced yeast protoplast reversion and hybrid formation. Autoclaving has been shown to cause PEG degradation and increase the acetaldehyde content. Consequently, membrane filtration is recommended as the optimum means of sterilising PEG solutions to ensure maximum protoplast reversion and hybrid yield.

We studied a series of test conditions in a microtiter system to define the optimal method for determining the susceptibility of Cryptococcus neoformans to antifungal agents. Twenty-one isolates of C. neoformans were grown for 24 or 48 h in four chemically defined media: yeast nitrogen base (BYNB 7); RPMI 1640; synthetic amino acid medium--fungal (SAAMF), buffered at pH 7.0 to select the medium that best supported growth of this fastidious yeast; and yeast nitrogen base, pH 5.4 (YNB 5.4). Maximum growth of C. neoformans, at 35 degrees C, was obtained in YNB 5.4, with the next highest growth levels in BYNB 7, SAAMF, and RPMI. Growth at 24 h was uniformly poor in all media and lacked reproducibility. In contrast, incubation for 48 h gave adequate growth with low standard deviations, and 48 h was selected as the optimal incubation period for this study. Comparison of the relationship between growth kinetics and initial inoculum size for eight cryptococcal isolates showed that 10(4) cells per ml yielded optimal growth in BYNB 7 and YNB 5.4, whereas 10(5) cells per ml was optimal in RPMI and SAAMF. Furthermore, variation of inocula from 10(3) to 10(5) cells per ml showed small but significant inoculum effects in determining MICs of fluconazole, amphotericin B, and flucytosine for C. neoformans. Therefore, 10(4) cells per ml was chosen as the optimal inoculum for susceptibility testing in this study. Mean MICs of fluconazole, amphotericin B, and flucytosine for 21 crytococcal isolates in RPMI and BYNB 7 were low (for example, fluconazole had mean MICs of 1.2 and 1.3 micrograms/ml in RPMI and BYNB 7, respectively) and differed significantly from medium to medium. In contrast, the MICs obtained in SAAMF were significantly higher (e.g., fluconazole had a mean MIC of 2.2 micrograms/ml). Variance in MICs was large with fluconazole and flucytosine but small with amphotericin B, irrespective of the medium used. A microtiter system employing BYNB 7 as the medium, 48 h as the incubation period, and 10(4) cells per ml as the final inoculum is a simple, accurate, and reproducible method for the testing of C. neoformans susceptibility to fluconazole, amphotericin B, and flucytosine.

The Candida albicans PLB1 gene was cloned using a polymerase chain reaction-based approach relying on degenerate oligonucleotide primers designed according to the amino acid sequences of two peptide fragments obtained from a purified candidal enzyme displaying phospholipase activity (Mirbod, F., Banno, Y., Ghannoum, M. A., Ibrahim, A. S., Nakashima, S., Yasuo, K., Cole, G. T., and Nozawa, Y. (1995) Biochim. Biophys. Acta 1257, 181-188). Sequence analysis of a 6.7-kilobase pair EcoRI-ClaI genomic clone revealed a single open reading frame of 1818 base pairs that predicts for a pre-protein of 605 residues. Comparison of the putative candidal phospholipase with those of other proteins in data base revealed significant homology to known fungal phospholipase Bs from Saccharomyces cerevisiae (45%), Penicillium notatum (42%), Torulaspora delbrueckii (48%), and Schizosaccharomyces pombe (38%). Thus, we have cloned the gene encoding a C. albicans phospholipase B homolog. This gene, designated caPLB1, was mapped to chromosome 6. Disruption experiments revealed that the caplb1 null mutant is viable and displays no obvious phenotype. However, the virulence of strains deleted for caPLB1, as assessed in a murine model for hematogenously disseminated candidiasis, was significantly attenuated compared with the isogenic wild-type parental strain. Although deletion of caPLB1 did not produce any detectable effects on candidal adherence to human endothelial or epithelial cells, the ability of the caplb1 null mutant to penetrate host cells was dramatically reduced. Thus, phospholipase B may well contribute to the pathogenicity of C. albicans by abetting the fungus in damaging and traversing host cell membranes, processes which likely increase the rapidity of disseminated infection.

Using an in vitro model of intravascular infection, we examined the effects of exposure to subinhibitory concentrations of fluconazole and amphotericin B on the ability of Candida albicans to adhere to and damage human umbilical vein endothelial cells. Incubation of the organisms for 18 h in 0.5x the MICs of fluconazole and amphotericin B inhibited endothelial cell adherence by 22 and 91%, respectively (P less than 0.001 for each drug). Candida-induced endothelial cell injury was also decreased by exposing the organisms to the antifungal drugs while in contact with the endothelial cells. Fluconazole inhibited damage by approximately 50% at concentrations ranging from 0.25x to 5x the MIC (P less than 0.01 for each concentration). Exposure to amphotericin B at 0.5x the MIC completely blocked the ability of the organisms to injure endothelial cells. The capacities of the antifungal agents to inhibit endothelial cell injury paralleled their abilities to suppress candidal germination. Organisms exposed to up to 5x the MIC of fluconazole had diminished, but still detectable, germ tube production and elongation, whereas incubation in 0.5x the MIC of amphotericin B completely abrogated germination. In addition to their direct effects on the growth of C. albicans, fluconazole and amphotericin B may decrease the ability of the fungus to disseminate hematogenously by inhibiting the organisms' capacity to adhere to and injure endothelial cells.