Activity of fluconazole (UK 49,858) and ketoconazole against Candida albicans in vitro and in vivo

Different components in human serum inhibit multiplication of Cryptococcus neoformans and enhance fluconazole activity

The inhibitory effect of human serum on the multiplication of Cryptococcus neoformans and the interaction with fluconazole were studied. Compared with cryptococcal multiplication in RPMI 1640 medium alone, 5% human serum in medium inhibited multiplication by 76% +/- 6% (n = 8). The inhibitory effect of human serum was donor independent, [corrected] heat stable (56 degrees C, 30 min), and not due to albumin or globulin. Bovine and murine sera were not inhibitory at that concentration. A fungistatic concentration of fluconazole (5.0 micrograms/ml) in medium plus 5% human serum resulted in 40% +/- 5% (n = 8) killing (reduction of inoculum CFU) in a 24-h assay. Bovine or murine sera did not have the enhancing effect, and this human serum activity was heat stable and donor independent. At 2.5 micrograms of fluconazole per ml, fungistasis by fluconazole plus human serum was significantly greater than with either alone. Higher serum concentrations [corrected] potentiated fluconazole more. At higher fluconazole concentrations (e.g., 20 micrograms/ml) fluconazole alone could kill, but serum potentiated this. A fluconazole-resistant isolate (MIC, 100 micrograms/ml) was not killed by fluconazole (5.0 micrograms/ml) in 5% human serum, but human serum potentiated the partial fluconazole inhibition. When human serum was dialyzed (molecular weight cutoff, 6,000 to 8,000) against phosphate-buffered saline, it lost the ability to synergize with fluconazole for killing Cryptococcus organisms but not the capacity to inhibit multiplication. Filtration of serum suggested the filtrate with a molecular weight of < 10,000 could interact synergistically with fluconazole for killing but could not inhibit cryptococcal multiplication. These findings indicate that human serum has two components, one (macromolecular) with a unique ability to inhibit C. neoformans and a low-molecular-weight component that enhances fluconazole anticryptococcal activity.

Resistance to antifungal agents

The marked increase in the number of patients with AIDS and other forms of immunocompromise has resulted in the emergence of fungi as predominant pathogens in many institutions. Unfortunately, with the widespread use of antifungal agents to combat these infections, reports of resistance to antifungal agents have proliferated. In the present environment, the occurrence of resistance to antifungal agents is neither rare nor of negligible clinical importance. The expanding demand for antifungal agents mandates a new sense of vigilance for resistance. Although newly proposed standards for in vitro susceptibility testing should help to remove the ambiguity surrounding quantitative measurement of fungal resistance, lessons learned in the treatment of bacteria clearly now apply to fungi also: prolonged use of an antimicrobial agent will result in the selection of resistant organisms. The enlarging spectrum of resistance to antifungal agents must prompt aggressive searches for new modes of therapy. Strategies to inhibit fungal colonization, to augment host defenses, or to develop novel antifungal agents from Pseudomonas syringae or from peptide nanotubes are helping to solve this pressing clinical need.

Increased resistance to antifungal antibiotics of Candida spp. adhered to silicone

The minimal inhibitory concentrations (MICs) and minimal fungicidal concentrations (MFCs) of amphotericin B, miconazole, ketoconazole, fluconazole, and itraconazole were determined for non-adhered cells and cells adhered to sections of a silicone urinary catheter. The densities of adhered cells were established with cells radiolabeled with tritiated leucine. Well defined MICs and MFCs were established for amphotericin B for representative adhered strains. In contrast, the azoles, especially fluconazole, did not give clear end points and the MICs and MFCs were arbitrarily determined. MFCs for the adhered cells generally were 2- to 5-fold higher than those of non-adhered cells. Techniques that include adhered-cell susceptibilities may be necessary before antifungal regimens for prosthetic device-associated yeast infections are appropriately defined.

Fluconazole response patterns in HIV-infected patients with oropharyngeal candidiasis

A prospective study to assess the efficacy of fluconazole in oropharyngeal candidiasis in patients with HIV was conducted. A cohort of 30 HIV-positive persons with clinical and microbiologic confirmed oropharyngeal candidiasis (Candida albicans > 1000 CFU/ml) received fluconazole 100 mg daily for 7 days. In vitro antifungal susceptibility tests demonstrated a lack of fluconazole resistances. Cultures of mouth swabs were performed at the end of therapy and 2 weeks later. There was a clinical and microbiologic cure in 26 patients (87%). In 10 of these 26, cultures remained negative after 2 weeks; most of them had CD4 lymphocyte count > 400/ml. In the other 16 patients (53%), cultures showed a microbiologic relapse 2 weeks after treatment. In spite of clinical improvement, treatment failure was observed in four patients, all of them with CD4 lymphocyte count < 50 ml.

Salivary concentrations of ketoconazole and fluconazole: implications for drug efficacy in oropharyngeal and esophageal candidiasis

OBJECTIVE

To determine whether salivary concentrations of ketoconazole and fluconazole may explain the apparent disparity between in vitro activity and clinical efficacy observed with these drugs.

DESIGN

Healthy subjects received a single oral dose of ketoconazole 400 mg or fluconazole 100 mg in a randomized, crossover fashion. Saliva was collected at 0, 1, 2, 3, 6, 12, and 24 hours. Blood samples were obtained at 2 and 24 hours. Salivary concentrations and plasma concentrations for each drug were determined by HPLC. Minimum inhibitory concentration (MIC) testing was determined in triplicate on 6 clinical isolates of Candida albicans, and times over the median MIC values were calculated.

PARTICIPANTS

Eight subjects completed the study.

RESULTS

The mean (+/- SD) peak salivary concentration for ketoconazole was 0.119 +/- 0.050 microgram/mL at 3 hours; no subject had a detectable ketoconazole salivary concentration at 24 hours. At 2 and 24 hours, mean ketoconazole plasma concentrations were 7.64 +/- 3.87 and 0.11 +/- 0.05 microgram/mL, respectively. The saliva to plasma concentration ratio at 2 hours was 0.01. The mean peak salivary concentration of fluconazole was 2.56 +/- 0.34 microgram/mL at 3 hours. At 24 hours, the mean salivary concentration was 1.44 +/- 0.33 microgram/mL. At 2 and 24 hours, mean fluconazole plasma concentrations were 4.39 +/- 3.33 and 3.72 +/- 2.83 micrograms/mL, respectively. The saliva to plasma concentration ratio at 2 hours was 0.55. Median MIC values were 0.0625 microgram/mL (range 0.0313-0.125) for ketoconazole and 0.25 microgram/mL (range 0.125-0.5) for fluconazole. Calculated times over which ketoconazole and fluconazole exceeded the median MICs in saliva were approximately 13 and greater than 24 hours, respectively.

CONCLUSIONS

After a single oral dose, fluconazole achieved higher salivary concentrations than did ketoconazole. This may explain the increased clinical efficacy of fluconazole in the treatment of oropharyngeal-esophageal candidiasis when compared with ketoconazole.

Antifungal agents: an overview. Part II

The recent introduction of a new generation of antifungal drugs promises to alter significantly therapy for both systemic and superficial mycoses, in particular, onychomycosis. This article presents an in-depth review of the azoles (the triazoles itraconazole and fluconazole), the allylamines (naftifine and terbinafine), and the morpholine derivative amorolfine.

Antagonistic effects of fluconazole and 5-fluorocytosine on candidacidal action of amphotericin B in human serum

This study addressed the effects of fluconazole and 5-fluorocytosine on the candidacidal activity of amphotericin B in the presence of human serum. A Candida albicans isolate that was susceptible to all three agents according to standard testing procedures was employed. Fungicidal activity was estimated by using a flow cytometric procedure that exploited the fact that yeast cells killed by amphotericin B diminish in size and take up propidium iodide. The following findings were made. (i) Fluconazole and 5-fluorocytosine each failed to inhibit pseudohyphal formation and cell aggregation even when applied at 10 and 50 micrograms/ml, respectively, for up to 10 h. Hence, these agents were not fungistatic when tested in the presence of serum. (ii) Simultaneous application of 5-fluorocytosine had neither enhancing nor inhibitory effects on the fungicidal activity of amphotericin B. However, yeasts that were preincubated for 20 h with 5-fluorocytosine became less susceptible to killing by amphotericin B. (iii) Fluconazole exerted a frank antagonistic effect on the fungicidal activity of amphotericin B. Thus, under our in vitro conditions, both fluconazole and 5-fluorocytosine can overtly antagonize the candidacidal action of amphotericin B.

In vitro susceptibility and sterol biosynthesis of Candida albicans strains after long-term treatment with azoles in HIV-infected patients

Over a period of 6 to 24 months a long term follow up of the in vitro antifungal susceptibility of 306 Candida albicans strains from 49 HIV-infected patients was performed. Using a microdilution test, the strains were tested against the azoles ketoconazole, itraconazole and fluconazole. The susceptibility range for fluconazole was between 1 and 128 mg/l, for itraconazole between 0.015 and 32 mg/l and for ketoconazole between 0.007 and 16 mg/l. 11.7% of the strains showed elevated IC30-values against ketoconazole, 9.1% against itraconazole and 10.1% against fluconazole. Sterol biosynthesis was examined by thin layer chromatography in 18 less sensitive strains and nine sensitive strains in the presence of ketoconazole. The proportion of ergosterol in the presence of ketoconazole at a concentration of 0.003 mg/l varied between 7.6% and 21.1% in sensitive strains and between 11.1% and 86.6% in less sensitive strains. In resistant control strains the proportion of ergosterol was 73% and 94.2%, respectively. Without ketoconazole the ergosterol proportion was > 85% in all strains. There was a significant correlation between the IC30-values and the inhibition of ergosterol biosynthesis (p = 0.05).

Fluconazole-resistant oral candidosis in a repeatedly treated female AIDS patient

A 29-year-old female suffering from full-blown AIDS received fluconazole 400 mg day-1 for a long period for treatment of oral candidosis, pseudomembranous type. She had previously received this drug repeatedly for the same reason, yet manifest disease persisted. She was therefore put on parenteral amphotericin B, which led to clinical, but not mycological, cure in the short term. IC30 testing revealed a minimum inhibitory concentration (MIC) > 128 micrograms ml-1 for fluconazole. The isolate, however, was susceptible in vitro to ketoconazole, itraconazole and amphotericin B. The same antimicrobial susceptibility pattern was found with a second isolate obtained later. Resistance to fluconazole might become a major problem in HIV-infected patients receiving this drug for long periods.

Improved medium for fluconazole susceptibility testing of Candida albicans

We have compared fluconazole susceptibilities of 92 clinical isolates of Candida albicans by broth microdilution in two different media: standard RPMI 1640 (RPMI) and the same medium supplemented with 18 g of glucose per liter (RPMI-glucose). Preparation of media, drugs, and inocula, as well as incubation conditions, followed the preliminary recommendations of the National Committee for Clinical Laboratory Standards (Villanova, Pa.) antifungal agent working group for broth macrodilution tests with antifungal agents, adapted to microdilution. Microtiter plates were agitated for 5 min before spectrophotometric readings were performed with an automatic plate reader set at 405 mm. The MIC endpoint was defined as an inhibitory concentration calculated from the turbidimetric data as a function of the turbidity in the drug-free control wells. The mean absorbances in the drug-free wells in RPMI and RPMI-glucose were, respectively, 0.38 (41.6% transmission) and 0.99 (10.2% transmission) (P < 0.001; Student's t test). Despite the increased growth in RPMI-glucose, 98.9% of the C. albicans strains tested for fluconazole susceptibility yielded similar MICs (+/- 1 dilution) in both media. Moreover, strains with decreased susceptibility to fluconazole displaying similar MICs in both media are easier to detect in RPMI-glucose because of the greater differences between turbidimetric readings in wells with grown or fluconazole-inhibited cultures. This objective turbidimetric method, with an easy-to-read improved medium (RPMI with glucose), together with previous experience of the National Committee for Clinical Laboratory Standards antifungal agent subcommittee, could overcome some of the present problems associated with lack of reproducibility of azole susceptibility testing.

Effect of antimicrobial and antineoplastic drugs on the uptake of fluconazole by human neutrophils and tissue culture cells

The effect of eight antimicrobial and three antineoplastic drugs on the uptake of fluconazole by human neutrophils and culture epithelial cells was evaluated. Fluconazole reached higher concentrations intracellularly than extracellularly (cellular to extracellular concentration ratio C/E > or = 1.3) in the presence of therapeutical concentrations of the antimicrobial and antineoplastic agents evaluated.

Antifungal susceptibility testing

Unlike antibacterial susceptibility testing, reliable antifungal susceptibility testing is still largely in its infancy. Many methods have been described, but they produce widely discrepant results unless such factors as pH, inoculum size, medium formulation, incubation time, and incubation temperature are carefully controlled. Even when laboratories agree upon a common method, interlaboratory agreement may be poor. As a result of numerous collaborative projects carried out both independently and under the aegis of the Subcommittee on Antifungal Susceptibility Testing of the National Committee for Clinical Laboratory Standards, the effects of varying these factors have been extensively studied and a standard method which minimizes interlaboratory variability during the testing of Candida spp. and Cryptococcus neoformans has been proposed. This review summarizes this work, reviews the strengths and weaknesses of the proposed susceptibility testing standard, and identifies directions for future work.

In vitro studies of a new antifungal triazole, D0870, against Candida albicans, Cryptococcus neoformans, and other pathogenic yeasts

We investigated the effects of various assay conditions on the activity of D0870 against seven species of fungi in the broth macrodilution testing procedure proposed by the National Committee for Clinical Laboratory Standards (NCCLS). Multivariate analysis demonstrated that endpoint definition, starting inoculum size, medium composition, type of buffer, and length of incubation, but not pH or temperature, had significant effects on results. Increasing the inoculum from 10(2) to 10(5) yeast cells/ml raised the MICs for all isolates up to > 75,000 fold. This effect was greatest when endpoints corresponded to a 90% reduction in visually determined turbidity (MIC90), was less prominent with an 80% inhibition visual endpoint (MIC80), and was nearly absent with a 50% endpoint measured by a spectrophotometer (IC1/2). Differences due to medium composition were attributable to antibiotic medium 3 with RPMI and yeast nitrogen base media performing nearly identically. Under standardized conditions as specified in NCCLS document M27-P (Reference Method for Broth Dilution Antifungal Susceptibility Testing of Yeasts; Proposed Standard, 1992), 79 strains (5 to 25 strains for each species) demonstrated median MIC80s of 0.0037 and 0.0075 microgram/ml for Candida albicans and Cryptococcus neoformans, respectively. In contrast, Candida krusei and Torulopsis glabrata had a median MIC80 of 1.0 microgram/ml. Our studies indicate that the pathogenic yeasts C. albicans and C. neoformans are more susceptible to D0870 than other pathogenic yeasts.

Influence of fluconazole on antipyrine kinetics in rats

The present study was undertaken to examine the effect of fluconazole on in vivo drug metabolism in rats, using the model substrate antipyrine. Oral doses of fluconazole, 20 mg/kg, were administered once (acutely) or twice daily for 4 days (chronically). Control animals received oral drug vehicle. Antipyrine kinetics were determined following an intravenous dose of 20 mg/kg given either 1 or 12 h after the single or last dose of fluconazole respectively. Acute fluconazole treatment significantly increased antipyrine half-life by 250% and reduced its clearance by 50%, without affecting its volume of distribution. Chronic treatment with fluconazole failed to affect antipyrine pharmacokinetics. This study demonstrates that acute fluconazole inhibits the metabolism of antipyrine in rats.

Pharmacokinetics of 18F-labeled fluconazole in healthy human subjects by positron emission tomography

The distribution of fluconazole in tissue of human volunteers was determined by positron emission tomographic scanning over a 2-h period following the infusion of a tracer dose of 18F-fluconazole (5 to 7 mCi) plus 400 mg of unlabeled drug (the standard daily dose of fluconazole). Previous studies have validated this approach for animals. From serial positron emission tomographic imaging and blood sampling, pharmacokinetics of fluconazole in tissue were determined. There was significant distribution of the radiolabeled drug in all organs studied, with nearly constant levels achieved by 1 h. Plateau concentrations of fluconazole in key organs (micrograms per gram) included the following: whole brain, 4.92 +/- 0.17; heart, 6.98 +/- 0.20; lung, 7.81 +/- 0.46; liver, 12.94 +/- 0.24; spleen, 22.96 +/- 2.5; kidney, 11.23 +/- 0.61; prostate, 8.24 +/- 0.58; and blood, 3.76 +/- 0.30. Since levels of fluconazole of > 6 micrograms/g are needed to treat infection with most strains of Candida and levels of > 10 micrograms/g are needed for Cryptococcus neoformans, Coccidioides immitis, and Histoplasma capsulatum, the following predictions can be made. The current standard dose of 400 mg/day should be more than adequate in the treatment of urinary tract and hepatosplenic candidiasis but problematic in the treatment of candidal osteomyelitis, even with the higher levels that develop after multiple doses. Similarly, higher doses should be considered, particularly in immunocompromised patients, with infection with C. neoformans, H. capsulatum, and C. immitis that involves the central nervous and musculoskeletal systems.

Determination of anti-Aspergillus activity of antifungal agents based on the dynamic growth rate of a single hypha

The dynamic growth rate of a single hypha of Aspergillus niger was analysed using an automatic system. A colony of A. niger was in contact with saline, saline containing an antifungal agent, and flushing saline, in sequence. The growth rate of a test hypha selected arbitrarily from the colony responded dynamically to the antifungal agent. The minimum concentration that caused the complete inhibition of hyphal growth was defined as the minimum inhibitory concentration (MIC). The MIC values obtained were compared with those determined by conventional methods based on increasing rate of colony diameter or dry matter weight.

Uptake and intracellular activity of fluconazole in human polymorphonuclear leukocytes

The penetration of fluconazole into human polymorphonuclear leukocytes (PMNs) and tissue culture epithelial cells (McCoy) was evaluated. At different extracellular concentrations (0.5 to 10 mg/liter), fluconazole reached cell-associated concentrations greater than the extracellular ones in either human PMNs (intracellular concentration to extracellular concentration ratio, > or = 2.2) or McCoy cells (intracellular concentration to extracellular concentration ratio, > or = 1.3). The uptake of fluconazole by PMNs was rapid and reversible but was not energy dependent. The intracellular penetration of fluconazole was not affected by environmental pH or temperature. Ingestion of opsonized zymosan and opsonized Candida albicans did not significantly increase the amount of PMN-associated fluconazole. At therapeutic extracellular concentrations, the intracellular activity of fluconazole against C. albicans in PMNs was significantly lower than that of amphotericin B. It was concluded that fluconazole reaches high intracellular concentrations within PMNs but shows moderate activity against intracellular C. albicans in vitro.

Clinical pharmacokinetics of fluconazole

Fluconazole was recently developed for the treatment of superficial and systemic fungal infections. Triazole groups and insertion of 2 fluoride atoms increase the polarity and hydrosolubility of the drug, allowing it to be used in a parenteral form. Bioassay methods using Candida pseudotropicalis as a test organism were the first techniques used for the determination of fluconazole in body fluids. Gas chromatographic and high performance liquid chromatographic methods were later developed with better accuracy and sensitivity. Prediction of efficacious concentrations in patients from the minimum inhibitory concentrations in vitro seems to be uncertain because of low efficacy of the drug on some yeasts in vitro compared with efficacy in vivo in animal models. Oral forms (capsule and solution) are quickly absorbed and bioavailability is nearly complete (about 90%). Plasma protein binding is low (11 to 12%) and fluconazole circulates as active drug. Distribution is extensive throughout the tissues and allows the treatment of a variety of systemic fungal infections. The average elimination half-life (t1/2) of 31.6 +/- 4.9h is long, with a minimum of 6 days needed to reach steady-state; thus, a loading dose (equal to double the maintenance dose) is recommended. The metabolism of fluconazole is not qualitatively or quantitatively significant. The main route of elimination is renal. The mean +/- SD (calculated from published data) total and renal clearance values are 19.5 +/- 4.7 and 14.7 +/- 3.7 ml/min (1.17 +/- 0.28 and 0.88 +/- 0.22 L/h), respectively. Concentrations of fluconazole in blood after administration of single doses correlated well with the administered dose. There was very little interassay variation between the data reported in literature. Concentrations in blood after multiple doses also exhibit little variation and the accumulation factor was between 2.1 and 2.8. Fluconazole was found in many body fluids, especially in cerebrospinal fluid and dialysis fluid, allowing the treatment of systemic fungal infections such as coccidioidal meningitis and fungal peritonitis. Concentrations of 1 to 3 mg/L and 20 mg/L are the extreme values expected in clinical practice. In renal insufficiency the fluconazole t1/2 is longer, requiring dosage adjustment in relation to creatinine clearance. In continuous ambulatory peritoneal dialysis a 150mg dose in a 2L dialysis solution every 2 days has been proposed. In haemodialysis, a dose of 100 or 200mg should be given at the end of each dialysis session. Neither old age nor irradiation affect fluconazole pharmacokinetics, but the t1/2 was shorter in children.(ABSTRACT TRUNCATED AT 400 WORDS)

Multicenter evaluation of a broth macrodilution antifungal susceptibility test for yeasts

Thirteen laboratories collaborated to optimize interlaboratory agreement of results of a broth macrodilution procedure for testing three classes of antifungal drugs against pathogenic yeasts. The activities of amphotericin B, flucytosine, and ketoconazole were tested against 100 coded isolates of Candida albicans, Candida tropicalis, Candida parapsilosis, Candida lusitaniae, Torulopsis (Candida) glabrata, and Cryptococcus neoformans. Two starting yeast inoculum sizes (5 x 10(4) and 2.5 x 10(3) cells per ml) were compared, and readings were taken after 24 and 48 h of incubation. All other test conditions were standardized. The resultant turbidities in all tubes were estimated visually on a scale from 0 to 4+ turbidity, and MIC-0, MIC-1, and MIC-2 were defined as the lowest drug concentrations that reduced growth to 0, 1+, or 2+ turbidity, respectively. For flucytosine, agreement among laboratories varied between 57 and 87% for different inocula, times of incubation, and end point criteria. Agreement was maximized (85%) when the lower inoculum was incubated for 2 days and the MICs were defined as 1+ turbidity or less. For amphotericin B, variations in test conditions produced much smaller differences in interlaboratory agreement. For ketoconazole, interlaboratory agreement was poorer by all end point criteria. However, MIC-2 endpoints distinguished T. glabrata as resistant compared with the other species. Overall, the studies indicated that readings from the lower inoculum obtained on the second day of reading result in the greatest interlaboratory agreement. In combination with data from previous multicenter studies (National Committee for Clinical Laboratory Standards, Antifungal Susceptibility Testing: Committee Report, Vol. 5, No. 17, 1988; M. A. Pfaller, L. Burmeister, M. S. Bartlett, and M. G. Rinaldi, J. Clin. Microbiol. 26:1437-1441, 1988; M. A. Pfaller, M. G. Rinaldi, J. N. Galgiani, M. S. Bartlett, B.A. Body, A. Espinel-Ingroff, R.A. Fromtling, G.S. Hall, C.E. Hughes, F. C. Odds, and A. M. SUgar, J. Clin. Microbiol. 34:1648-1654, 1990), these findings will be used by the National Committee for Clinical Laboratory Standards to develop a standardized method for in vitro antifungal susceptibility testing for yeasts.

Efficacy of fluconazole in the treatment of systemic fungal infections

The efficacy of fluconazole in the treatment of systemic fungal infections was evaluated in an open non-comparative trial. A total of 48 patients with proven or suspected fungal infections were enrolled in 40 of whom efficacy was evaluable. Candida albicans accounted for 90% of the infections. Candida parapsilosis, Candida glabrata, Histoplasma capsulatum and Aspergillus fumigatus caused the infection in one case each. Fluconazole was administered at a dosage of 200-400 mg daily for a mean duration of 15 days. Fluconazole treatment was successful in 53% of the patients. In patients with proven or probable Candida albicans infections a clinical and mycological response was achieved in 62% and 65%, respectively. In 11 patients elevation of liver enzymes was considered to be possibly related to fluconazole treatment; modification of treatment was not necessary in any case. Fluconazole was found to be a well tolerated and effective agent for the treatment of systemic Candida albicans infections.

In vitro activity of cloconazole, sulconazole, butoconazole, isoconazole, fenticonazole, and five other antifungal agents against clinical isolates of Candida albicans and Candida spp

The in vitro activity of several new imidazoles, cloconazole, sulconazole, butoconazole, isoconazole and fenticonazole, were compared with those of amphothericin B, flucytosine, and three azoles: econazole, miconazole and ketoconazole against isolates of pathogenic Candida. A total of 186 clinical isolates of 10 species of the genus Candida and two culture collection strains were tested by an agar-dilution technique. Isoconazole was the most active azole, followed by butoconazole sulconazole. Differences between some of the species in their susceptibility to the antifungal agents were noted. Sulconazole and cloconazole had the highest activity in vitro against 106 isolates of C. albicans. Butoconazole and isoconazole were also very active against isolates of C. albicans, and were the most active azole compounds against 80 isolates of Candida spp.

Effects of amphotericin B and fluconazole on the extracellular and intracellular growth of Candida albicans

The effects of amphotericin B and fluconazole on the extracellular and intracellular growth of Candida albicans were studied. With respect to the extracellular growth of C. albicans, antifungal activity was measured in terms of MICs and minimal fungicidal concentrations as well as by determination of the concentration that effectively killed (greater than 99.9%) C. albicans in the absence or presence (amphotericin B only) of serum. Amphotericin B was highly active in terms of killing, even at an increased inoculum size. In the presence of serum, amphotericin B activity was substantially reduced. For fluconazole, activity was restricted to inhibition of fungal growth, even after the inoculum size was reduced. With respect to the intracellular growth of C. albicans, antifungal activity was measured by using monolayers of murine peritoneal macrophages infected with C. albicans and was measured in terms of inhibition of germ tube formation as well as effective killing (greater than 99%) of C. albicans. Amphotericin B was highly active against C. albicans. At an increased ratio of infection, amphotericin B activity was slightly reduced. Fluconazole had no antifungal activity. Neither a reduction in the ratio of infection nor exposure of C. albicans to fluconazole prior to macrophage ingestion resulted in activity against intracellular C. albicans by fluconazole. Previous exposure of C. albicans to amphotericin B resulted in increased intracellular activity of amphotericin B. The intracellular antifungal activity of the combination of fluconazole with amphotericin B was less than that of amphotericin B alone. Amphotericin B showed fungicidal activity against C. albicans growing both extracellularly and intracellularly, whereas fluconazole inhibited growth only of extracellular C. albicans. A slight antagonistic effect between fluconazole and amphotericin B was found with respect to intracellular as well as extracellular C. albicans.

In vitro and in vivo antifungal activities of BMY-28864, a water-soluble pradimicin derivative

BMY-28864, a water-soluble pradimicin derivative, had potent in vitro activity against a wide variety of fungi, including those associated with deep-seated mycosis; it inhibited the growth of standard strains and clinical isolates at concentrations of 12.5 micrograms/ml or less. At the MIC or higher concentrations, BMY-28864 was fungicidal for Candida albicans under both growing and nongrowing conditions. BMY-28864 expressed fungicidal activity only in the presence of Ca2+, and its activity was totally diminished when ethylene glycol-bis(2-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), a Ca2+ chelator, was added to the test medium. The effectiveness of intravenously administered BMY-28864 in vivo was examined and compared with that of amphotericin B in mouse models of fungal infections. Both normal and cyclophosphamide-treated immunosuppressed mice infected with C. albicans, Cryptococcus neoformans, or Aspergillus fumigatus responded to therapy with BMY-28864 (50% protective doses of 17, 18, and 37 mg/kg of body weight in normal mice and of 32, 35, and 51 mg/kg in cyclophosphamide-treated mice, respectively). Lethal lung infections were also established with C. albicans or A. fumigatus in cyclophosphamide-treated mice. The 50% protective doses of BMY-28864 were 15 and 23 mg/kg per dose against C. albicans and A. fumigatus, respectively. The immunosuppression induced by intraperitoneal administration of 200 mg of cyclophosphamide per kg lasted for 5 days, and total recovery was observed by day 7.

Fluconazole susceptibility testing of Candida albicans: microtiter method that is independent of inoculum size, temperature, and time of reading

In vitro antifungal susceptibility testing generally remains unstandardized and unreliable for directing therapy. When azoles are tested, this problem is further compounded by the lack of definite reading end points. We determined the in vitro susceptibility of 50 Candida albicans isolates (including 10 reference strains) to fluconazole by using a microbroth dilution method in which microtiter plates were agitated immediately before reading. Six fungal inoculum sizes (ranging from 2 x 10(2) to 4 x 10(5) CFU/ml), three different times of reading (24, 48, and 72 h), and two temperatures (30 and 35 degrees C) were tested. We also compared visual and spectrophotometric determinations of MIC end points. This agitation method resulted in clear-cut visual end points that were reproducible for different observers within the same laboratory, that were independent of inoculum size, temperature of incubation, and time of reading, and that correlated well with the degree of fungal inhibition as determined by spectrophotometry. Median MICs also correlated with usually achievable levels of fluconazole in serum and tissue of humans and experimental animals.

Effect of culture media on in vitro susceptibility testing of fluconazole against some yeasts

Thirty clinical isolates, comprising six strains of Candida albicans, and four strains each of C. lusitaniae, C. parapsilosis, C. tropicalis, Cryptococcus neoformans, Torulopsis glabrata and Trichosporon beigelii were tested against fluconazole, using Sabouraud's dextrose (SD) broth and a high resolution (HR) medium (Pfizer Central Research, Inc.). The procedure was a standard tube (1 ml/tube) dilution, and C. albicans Y01 09 was included as a reference strain to monitor quality and reproducibility. Results indicated that the minimum inhibitory concentrations (MICs) for all isolates of C. albicans, C. lusitaniae, C. tropicalis, and Tr. beigelii were 100 micrograms ml-1 or greater in the SD medium. In the HR medium, however, the MICs for two isolates of C. albicans were 1.56 micrograms ml-1, in other four gave higher values (greater than 100 micrograms ml-1), and the results for C. lusitaniae and Tr. beigelii were in the range 1.56-3.12 micrograms ml-1. The MICs for C. tropicalis were unaffected (100 micrograms ml-1) by the medium used. All Cr. neoformans isolates yielded a uniform value (1.56 micrograms ml-1) in HR medium as compared to somewhat more variable results (MICs 0.39-1.56 micrograms ml-1) in SD broth. The MICs for T. glabrata in the SD and HR media were 3.12-12.5 and 6.25 micrograms ml-1, respectively. The data indicated that the HR medium is preferable for the in vitro susceptibility testing of C. albicans, C. lusitaniae and Tr. beigelii to fluconazole. The MICs for other yeasts were not affected by the culture medium. The reference C. albicans isolate yielded an MIC of 1.56 micrograms ml-1 throughout.

Fluconazole, itraconazole and ketoconazole in-vitro activity. A comparative study

We compared in-vitro activity of fluconazole, itraconazole and ketoconazole by evaluating their Minimal Inhibitory Concentrations (MICs) for 100 fungal strains isolated from different biological specimens of ARC/AIDS patients. A semisolid agar medium was used: this method is suitable for testing molds and yeasts, and can be applied to all azole antifungal drugs. Fluconazole had higher MICs than two other tested drugs, especially for Candida krusei strains; however it never had a MIC higher than 40 mg/l. Itraconazole and ketoconazole had MICs higher than 40mg/l for one Cryptococcus neoformans strain. There were no significant differences for itraconazole and ketoconazole among the tested strains.

Comparative study of fluconazole and clotrimazole in the treatment of vulvovaginal candidiasis

Fluconazole is a new oral triazole antifungal with good activity against Candida spp. In this study, we investigated the effectiveness and tolerability of a three-day course of treatment with fluconazole compared with clotrimazole vaginal tablets in nonpregnant women with acute Candida vaginitis. Of the 90 evaluable patients who received fluconazole, 76 (84 percent) were asymptomatic seven to ten days after treatment compared with 84 of 95 (88 percent) treated with clotrimazole. An additional ten patients in the fluconazole group (11 percent) and seven in the clotrimazole group (7 percent) had improvement in their signs and symptoms. Only four patients in each group (4 percent) were considered treatment failures. Mycological cures were obtained in 89 and 93 percent of patients treated with fluconazole and clotrimazole, respectively, seven to ten days posttreatment. Clinical cure rates remained high one month posttreatment: 79 percent in the fluconazole group and 83 percent in the clotrimazole group. Both therapies were well tolerated. One patient discontinued treatment after she developed diarrhea while receiving fluconazole. The most common adverse effects associated with fluconazole use were nausea (six percent) and diarrhea (three percent). No clinically significant laboratory abnormalities were observed. In this investigation, oral fluconazole therapy was found to be as safe and effective as clotrimazole vaginal tablets in women with acute vulvovaginal candidiasis.

Induction of fluconazole metabolism by rifampin: in vivo study in humans

The effects of rifampin on the pharmacokinetics of fluconazole were analyzed in an open-label, placebo-controlled, parallel study. Sixteen healthy male volunteers, randomized into two groups, received 200 mg of oral fluconazole on days 1 and 22. On days 8 through 27, group I received oral rifampin, 600 mg/d, and group II received placebo. Fluconazole in serum was analyzed by HPLC. On days 1 and 22, respectively, the AUC (micrograms.hr/mL) (mean +/- SD) was 160.5 +/- 19.5 and 124 +/- 22.2 in group I, 152 +/- 25 and 152.8 +/- 33.9 in group II; the Kel (hr-1) was .0211 +/- .0030 and .0264 +/- .0040 in group I, .0219 +/- .0036 and .0216 +/- .0053 in group II. Cmax and Tmax did not change significantly in either group. Urinary 6 beta-hydroxycortisol/cortisol increased from 3.47 +/- 1.04 to 15.2 +/- 5.07 in group I, but was unchanged (3.54 +/- 1.33-4.26 +/- 2.36) in group II on days 1 and 22, respectively. The findings in this study indicate that rifampin induces the metabolism of fluconazole.

Fluconazole for oropharyngeal candidiasis in anti-HIV positive haemophiliacs

Candidiasis of the oropharynx and oesophagus is one of the most common problems encountered in patients with HIV disease. Fluconazole is a bis-triazole antifungal agent with a long serum half-life. Sixteen anti-HIV positive patients (15 haemophiliacs and one blood transfusion recipient) with a clinical diagnosis of oropharyngeal candidiasis were treated with 50 mg fluconazole daily for 14-28 days and then either 150 mg fluconazole or placebo weekly for 6 months in a prophylactic phase. Clinical cure occurred in all patients, and mycological cure occurred in 13/16 (81%) patients. In the prophylactic phase, there were 2/5 (40%) relapses in the placebo arm compared with 1/8 (12.5%) in the fluconazole arm, but this was not statistically significant by Fisher's one-sided exact test (P = 0.31). It is concluded that fluconazole is an effective treatment of oropharyngeal candidiasis and has potential for prophylactic use.

Comparison of fluconazole and amphotericin B for treatment of disseminated candidiasis and endophthalmitis in rabbits

We compared the efficacy of intravenous fluconazole (80 mg/kg of body weight per day) with that of amphotericin B (1 mg/kg/day) for the long-term treatment of endophthalmitis in rabbits with disseminated candidiasis. After 17 days of therapy, fluconazole decreased the fungal colony counts of the choroid-retinas significantly more than did the saline control (P less than 0.05); however, after 24 days of fluconazole therapy, this treatment effect was lost and fluconazole was no more effective than saline. In contrast, treatment for 24 days with amphotericin B reduced the vitreous and choroid-retina fungal colony counts significantly more than either fluconazole or saline (P less than 0.05 for both treatment groups). After 17 days of therapy, indirect ophthalmoscopy revealed less severe eye involvement in both antifungal treatment groups than in saline controls; however, this difference reached statistical significance only for the amphotericin B-treated rabbits (P less than 0.05). Also, there was a trend towards worsening eye lesions, as seen by indirect ophthalmoscopy, in the fluconazole-treated rabbits after 24 days of therapy, which roughly paralleled the quantitative culture results. Despite the presence of negative choroid-retina cultures, some rabbits in all treatment groups had persistently visible eye lesions, indicating that ophthalmoscopic resolution of Candida endophthalmitis may lag behind lesion sterilization. Amphotericin B was superior to fluconazole in the treatment of Candida endophthalmitis in this model.

In-vitro comparative activity of fluconazole and other antifungal agents against Blastoschizomyces capitatus

Blastoschizomyces capitatus represents an emerging fungal pathogen in acute leukemia patients. The susceptibility to amphotericin B, 5-fluorocytosine, ketoconazole and fluconazole of nine clinical isolates was evaluated. A specific medium (high resolution medium) was used for testing fluconazole. This agent and 5-fluorocytosine were at least four- to eight-fold more active than amphotericin B and ketoconazole against all isolates but one.

Successful treatment of Candida osteomyelitis with fluconazole. A noncomparative study of two patients

We describe two patients with osteomyelitis due to Candida spp. treated with fluconazole, a new triazole antifungal. One patient had extensive involvement of ribs and costochondral regions of the anterior chest, and the other had vertebral infection. Both were cured with courses of 10 and 14 months, with greater than or equal to 1 year of follow-up after fluconazole was discontinued. Fluconazole is an attractive agent for the treatment of Candida osteomyelitis and deserves to be studied more extensively for this indication.