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

Enhancing the Antifungal Activity and Ophthalmic Transport of Fluconazole from PEGylated Polycaprolactone Loaded Nanoparticles

Fungal eye infections are caused mainly by an eye injury and can result in serious eye damage. Fluconazole (FLZ), a broad-spectrum antifungal agent, is a poorly soluble drug with a risk of hepatotoxicity. This work aimed to investigate the antifungal activity, ocular irritation, and transport of FLZ-loaded poly (ε-caprolactone) nanoparticles using a rabbit eye model. Three formulation factors affecting the nanoparticle's size, zeta potential, and entrapment efficiency were optimized utilizing the Box-Behnken design. Morphological characteristics and antifungal activity of the optimized nanoparticles were studied. The optimized nanoparticles were loaded into thermosensitive in situ hydrogel and hydroxypropylmethylcellulose (HPMC) hydrogel ophthalmic formulations. The rheological behavior, in vitro release and in vivo corneal transport were investigated. Results revealed that the percentage of poly (ε-caprolactone) in the nanoparticle matrix, polymer addition rate, and mixing speed significantly affected the particle size, zeta potential, and entrapment efficiency. The optimized nanoparticles were spherical in shape and show an average size of 145 nm, a zeta potential of -28.23 mV, and a FLZ entrapment efficiency of 98.2%. The antifungal activity of FLZ-loaded nanoparticles was significantly higher than the pure drug. The developed ophthalmic formulations exhibited a pseudoplastic flow, prolonged the drug release and were found to be non-irritating to the cornea. The prepared FLZ pegylated nanoparticles were able to reach the posterior eye segment without eye irritation. As a result, the developed thermosensitive in situ hydrogel formulation loaded with FLZ polymeric nanoparticles is a promising drug delivery strategy for treating deep fungal eye infections.

Fungal Endophthalmitis: A Comprehensive Review

Endophthalmitis is a serious ophthalmologic condition involving purulent inflammation of the intraocular spaces. The underlying etiology of infectious endophthalmitis is typically bacterial or fungal. The mechanism of entry into the eye is either exogenous, involving seeding of an infectious source from outside the eye (e.g., trauma or surgical complications), or endogenous, involving transit of an infectious source to the eye via the bloodstream. The most common organism for fungal endophthalmitis is Candida albicans. The most common clinical manifestation of fungal endophthalmitis is vision loss, but other signs of inflammation and infection are frequently present. Fungal endophthalmitis is a clinical diagnosis, which can be supported by vitreous, aqueous, or blood cultures. Treatment involves systemic and intravitreal antifungal medications as well as possible pars plana vitrectomy. In this review, we examine these essential elements of understanding fungal endophthalmitis as a clinically relevant entity, which threatens patients’ vision.

Clinical Practice Guideline for the Management of Candidiasis: 2016 Update by the Infectious Diseases Society of America

It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.

Innocent until proven guilty: mechanisms and roles of Streptococcus-Candida interactions in oral health and disease

Candida albicans and streptococci of the mitis group colonize the oral cavities of the majority of healthy humans. While C. albicans is considered an opportunistic pathogen, streptococci of this group are broadly considered avirulent or even beneficial organisms. However, recent evidence suggests that multi-species biofilms with these organisms may play detrimental roles in host homeostasis and may promote infection. In this review we summarize the literature on molecular interactions between members of this streptococcal group and C. albicans, with emphasis on their potential role in the pathogenesis of opportunistic oral mucosal infections.

Hosting infection: experimental models to assay Candida virulence

Although normally commensals in humans, Candida albicans, Candida tropicalis, Candida parapsilosis, Candida glabrata, and Candida krusei are capable of causing opportunistic infections in individuals with altered physiological and/or immunological responses. These fungal species are linked with a variety of infections, including oral, vaginal, gastrointestinal, and systemic infections, with C. albicans the major cause of infection. To assess the ability of different Candida species and strains to cause infection and disease requires the use of experimental infection models. This paper discusses the mucosal and systemic models of infection available to assay Candida virulence and gives examples of some of the knowledge that has been gained to date from these models.

The Effects of Caspofungin and Voriconazole in Experimental Candida Endophthalmitis

PURPOSE

To evaluate the efficacy of newly developed antifungal agents caspofungin and voriconazole in Candida albicans endophthalmitis in rabbit eyes.

METHODS

Thirty New Zealand white rabbits were divided into four treatment groups and one control group. One eye of each rabbit was infected by inoculation of 1 x 10(4) CFU/ml of C. albicans. Seventy-two hours after the inoculation, caspofungin 100 microg/0.1 ml in group 1 (n = 6), voriconazole 50 microg/0.1 ml in group 2 (n = 6), amphotericin B 10 microg/0.1 ml in group 3 (n = 6), itraconazole 10 microg/0.1 ml in group 4 (n = 6), and 0.1 ml NaCl 0.9% in control group (n = 6) were injected into the vitreous cavity. Clinical and histopathologic examination scores and microbiological analysis of vitreous aspirates were compared.

RESULTS

There was statistically significant difference in the clinical scores, histopathologic scores, and mean CFU/ml between the treatment and control groups (p < 0.05). In caspofungin and voriconazole groups, histopathologic scores and mean CFU were lower than other treatment groups and control group.

CONCLUSIONS

Intravitreal injection of caspofungin and voriconazole was effective against C. albicans endophthalmitis in this experimental rabbit model.

Vitrectomy with Fluconazole Infusion: Retinal Toxicity, Pharmacokinetics, and Efficacy in the Treatment of Experimental Candidal Endophthalmitis

The aim of this study was to determine the retinal toxicity and intraocular pharmacokinetics of vitrectomy with fluconazole infusion in rabbit eyes and to study its efficacy in the treatment of experimental candidal endophthalmitis. The right eyes of 13 New Zealand White (NZW) rabbits were vitrectomized and infused with 20 mL of 0.2 mg/mL, 1 mg/mL, or 2 mg/mL of fluconazole. An electroretinogram (ERG) was performed on both eyes of each rabbit at different time points. The right eyes of 26 different NZW rabbits were vitrectomized and infused with 20 mL of 2 mg/mL of fluconazole. These rabbits were sacrificed, and their right eyes were enucleated at hours 2, 4, 8, and 24 after the operation, and the concentration of fluconazole in the vitreous was measured by highpressure liquid chromatography. Experimental candidal endophthalmitis was induced in the right eye of 42 other NZW rabbits. Twenty-six (26) of the eyes were then vitrectomized and infused with 20 mL of 2 mg/mL of fluconazole, and the other 16 rabbits served as control. Severity of ocular infection was graded from 0-4 at different time intervals, using an indirect ophthalmoscope. In the first group, ERG showed no significant difference between the experimental eyes and the control eyes--in all concentrations of fluconazole--for up to 3 months. In the second group, the intraocular concentration of fluconazole declined so rapidly that, as of 8 hours after operation, there was none in the vitreous cavity. In the third group, significantly less vitreous opacity was found in the treated eyes on days 3 and 6. However, the difference ceased to be apparent on day 15. Our study suggests that there is no retinal toxicity resulting from vitrectomy with a 2 mg/mL fluconazole infusion, and that it is temporally effective in the treatment of experimental candidal endophthalmitis.

Endogenous endophthalmitis: an 18-year review of culture-positive cases at a tertiary care center

A retrospective chart review of all patients seen at the Cleveland Clinic Foundation with infectious endogenous endophthalmitis between January 1982 and August 2000 revealed 34 affected eyes in 27 patients. During this time, the median incidence of endogenous endophthalmitis was 1.8 cases/year, and 48.1% of patients presented as outpatients. Twenty-six patients presented to an ophthalmologist, and the diagnosis was initially missed in almost half the cases. Eleven patients had an unremarkable physical exam except for eye findings. We found an equal incidence of bacterial and fungal endophthalmitis and a predominance of among the fungal etiologic agents. We did not, however, note a predominance of Gramnegative organisms seen mostly in reports from Asia. The microbiologic diagnosis was based on aqueous and vitreous cultures or positive eye histopathology stains in almost two-thirds of cases. The sensitivity of the Gram stain was poor, but its specificity and positive predictive value were excellent. The vitreous cultures obtained by vitrectomy instruments were more sensitive in making the diagnosis than the vitreous needle biopsy. Aside from blood cultures and eye specimen cultures, half the patients had an additional infectious focus, most frequently a urinary tract infection, whereas infectious endocarditis was seen in a small minority. Twelve patients had visual improvement with treatment with a final visual acuity better than 20/200 in 44% of the eyes. Good visual outcome was associated with visual acuity of 20/200 or better at diagnosis and with the absence of hypopyon.

Fungal and parasitic infections of the eye

The unique structure of the human eye as well as exposure of the eye directly to the environment renders it vulnerable to a number of uncommon infectious diseases caused by fungi and parasites. Host defenses directed against these microorganisms, once anatomical barriers are breached, are often insufficient to prevent loss of vision. Therefore, the timely identification and treatment of the involved microorganisms are paramount. The anatomy of the eye and its surrounding structures is presented with an emphasis upon the association of the anatomy with specific infection of fungi and parasites. For example, filamentous fungal infections of the eye are usually due to penetrating trauma by objects contaminated by vegetable matter of the cornea or globe or, by extension, of infection from adjacent paranasal sinuses. Fungal endophthalmitis and chorioretinitis, on the other hand, are usually the result of antecedent fungemia seeding the ocular tissue. Candida spp. are the most common cause of endogenous endophthalmitis, although initial infection with the dimorphic fungi may lead to infection and scarring of the chorioretina. Contact lens wear is associated with keratitis caused by yeasts, filamentous fungi, and Acanthamoebae spp. Most parasitic infections of the eye, however, arise following bloodborne carriage of the microorganism to the eye or adjacent structures.

Fungal and parasitic infections of the eye

The unique structure of the human eye as well as exposure of the eye directly to the environment renders it vulnerable to a number of uncommon infectious diseases caused by fungi and parasites. Host defenses directed against these microorganisms, once anatomical barriers are breached, are often insufficient to prevent loss of vision. Therefore, the timely identification and treatment of the involved microorganisms are paramount. The anatomy of the eye and its surrounding structures is presented with an emphasis upon the association of the anatomy with specific infection of fungi and parasites. For example, filamentous fungal infections of the eye are usually due to penetrating trauma by objects contaminated by vegetable matter of the cornea or globe or, by extension, of infection from adjacent paranasal sinuses. Fungal endophthalmitis and chorioretinitis, on the other hand, are usually the result of antecedent fungemia seeding the ocular tissue. Candida spp. are the most common cause of endogenous endophthalmitis, although initial infection with the dimorphic fungi may lead to infection and scarring of the chorioretina. Contact lens wear is associated with keratitis caused by yeasts, filamentous fungi, and Acanthamoebae spp. Most parasitic infections of the eye, however, arise following bloodborne carriage of the microorganism to the eye or adjacent structures.

Efficacies of high-dose fluconazole plus amphotericin B and high-dose fluconazole plus 5-fluorocytosine versus amphotericin B, fluconazole, and 5-fluorocytosine monotherapies in treatment of experimental endocarditis, endophthalmitis, and pyelonephritis due to Candida albicans

We compared the efficacies of fluconazole (Flu), amphotericin B (AmB), and 5-fluorocytosine (5FC) monotherapies with the combination of Flu plus 5FC and Flu plus AmB in a rabbit model of Candida albicans endocarditis, endophthalmitis, and pyelonephritis. The dose of Flu used was that which resulted in an area under the concentration-time curve in rabbits equivalent to that seen in humans who receive Flu at 1,600 mg/day, the highest dose not associated with central nervous system toxicity in humans. Quantitative cultures of heart valve vegetations, the choroid-retina, vitreous humor, and kidney were conducted after 1, 5, 14, and 21 days of therapy. All untreated controls died within 6 days of infection; animals treated with 5FC monotherapy all died within 18 days. In contrast, 93% of animals in the other treatment groups appeared well and survived until they were sacrificed. At day 5, the relative decreases in CFU per gram in the vitreous humor were greater in groups that received Flu alone and in combination with 5FC or AmB than in groups receiving AmB or 5FC monotherapies (P < 0. 005) but were similar thereafter. In the choroid-retina, 5FC was the least-active drug. However, there were no differences in choroidal fungal densities between the other treatment groups. On days 5 and 14 of therapy, fungal densities in kidneys of AmB recipients were lower than those resulting from the other therapies (P < 0.001 and P < or = 0.038, respectively) and AmB-plus-Flu therapy was antagonistic; however, all therapies for fungal pyelonephritis were similar by treatment day 21. While fungal counts in cardiac valves of Flu recipients were similar to those of controls on day 5 of therapy and did not change from days 1 to 21, AmB therapy significantly decreased valvular CFUs versus Flu at days 5, 14, and 21 (P < 0.005 at each time point). 5FC plus Flu demonstrated enhanced killing in cardiac vegetations compared with Flu or 5FC as monotherapies (P < 0. 03). Similarly, the combination of AmB and Flu was more active than Flu in reducing the fungal density in cardiac vegetations (P < 0.03). However, as in the kidney, AmB plus Flu demonstrated antagonism versus AmB monotherapy in the treatment of C. albicans endocarditis (P < 0.05, P = 0.036, and P < 0.008 on days 5, 14, and 21, respectively).

Comparison of fluconazole pharmacokinetics in serum, aqueous humor, vitreous humor, and cerebrospinal fluid following a single dose and at steady state

The objective of this study was to characterize the pharmacokinetic parameters and penetration of fluconazole following a single dose in the serum, aqueous humor, vitreous humor and cerebrospinal fluid (CSF) of non pigmented rabbits using serial sampling techniques and to determine if the pharmacokinetic parameters in the eye and CSF are similar. Twenty healthy male rabbits received intravenous fluconazole 20 mg/kg as a single dose or 20 mg/kg every 12 hours for 4 doses. Serum, aqueous humor, vitreous humor and CSF samples were taken 15 minutes after the initial intravenous injection and hourly thereafter for six hours. Fluconazole concentrations were determined by microbiological assay. Pharmacokinetic analyses were performed using a nonlinear least-square regression program. Fluconazole's penetration in all anatomical compartments was > 70% than in the serum. Similar elimination half-lives and time to reach maximum concentrations were noted in all compartments. While mean concentrations in each anatomical compartment were similar in animals receiving a single dose or among those at serum steady state, the mean concentrations achieved in the serum, aqueous and vitreous humors and CSF were between 1.82 and 2.17 times higher at serum steady state than following a single dose. At serum concentrations that are comparable to those in humans, the penetration of fluconazole into the noninflamed aqueous and vitreous humors and CSF were > or = 70%. The CSF and ocular pharmacokinetic parameters closely resembled each other, so that either could be used as a surrogate for the other.

Pharmacokinetic studies of fluconazole in rabbits characterizing doses which achieve peak levels in serum and area under the concentration-time curve values which mimic those of high-dose fluconazole in humans

We conducted steady-state pharmacokinetic studies with high-dose fluconazole with rabbits and human volunteers. We then derived mathematical equations that predict the doses of fluconazole that should be given to rabbits to produce 24-h area under the concentration-time curve values and maximum concentrations in serum that are similar to those measured for humans given 800 to 2,000 mg of fluconazole per day. These equations provide a rational basis for designing future efficacy studies with rabbits and in evaluating the strength with which results of previously conducted studies using rabbit infection models can be extrapolated to the clinic.

Multicenter randomized trial of fluconazole versus amphotericin B for treatment of candidemia in non-neutropenic patients. Canadian Candidemia Study Group

A randomized trial was conducted to compare the efficacy and safety of fluconazole versus that of amphotericin B in the treatment of candidemia in non-neutropenic adults. Enrollment was stratified by disease severity (APACHE II score). Patients were randomized (1:1) to receive amphotericin B 0.6 mg/kg/day (cumulative dose 8 mg/kg) or fluconazole 800 mg intravenous loading dose, then 400 mg daily for four weeks (intravenous for at least 10 days). Patients were monitored for six months. A total of 106 patients were enrolled. A protocol amendment implemented midway through the trial required patients to be removed from the study and treated with amphotericin B if species identification indicated candidemia due to Candida glabrata or Candida krusei. Baseline characteristics were similar for the two groups; 103 patients (fluconazole, 50; amphotericin B, 53) met the major enrollment criteria. The intention-to-treat analysis indicated successful therapy in 50% of fluconazole recipients compared to 58% of the amphotericin B group (p = 0.39; one-sided 95% CI, -8 to 24%). The efficacy analysis included 84 patients (fluconazole, 42; amphotericin B, 42); successful outcomes were observed in 57% and 62% of cases in the fluconazole and amphotericin B groups, respectively (p = 0.66: one-sided 95% CI, -12 to 22%). The mortality at day 14 for the fluconazole group was 26% and for the amphotericin B group 21% (p = 0.52; chi-square test) and remained similar throughout the course of follow-up, Drug-related adverse events were more frequent with amphotericin B than with fluconazole and prompted switching of therapy for two (4%) and zero cases, respectively. Fluconazole and amphotericin B were associated with similar clinical response rates and survival in the treatment of candidemia among non-neutropenic patients; however, drug-related adverse events were more frequent with amphotericin B.

Fluconazole in Candida albicans sepsis during pregnancy: case report and review of the literature

Candida sepsis during pregnancy is a rare but life-threatening complication of infection with Candida albicans. In contrast to the situation with other antimicrobial agents, there exists only limited experience with systemic antifungal therapy during pregnancy. A recent report focuses on amphotericin B treatment in systemic fungal infection during pregnancy. The present report discusses a pregnant patient with Candida albicans sepsis and endophthalmitis as well as candida infection of the oral and genital mucous membranes, after hyperalimentation and broad spectrum antibiotic therapy via a central venous catheter. The patient was treated with 10 mg/kg fluconazole from week 16 of gestation for a total duration of 50 days. Adverse effects did not occur and the rest of the pregnancy proceeded favourably for both the mother and the baby.

Comparison of fluconazole and amphotericin B for treatment of experimental Candida albicans endocarditis in rabbits

Amphotericin B (AmB) and fluconazole, administered intraperitoneally for 7 days, were compared in a rabbit model for Candida albicans endocarditis. When given early, AmB was more effective than fluconazole for reducing CFU counts in vegetations (P < 0.01) and kidneys. Forty-eight hours after the last dose, AmB was still detected in all vegetations whereas fluconazole was detected in only one case.

Treatment of exogenous Candida endophthalmitis in rabbits with oral fluconazole

We investigated the efficacy of oral fluconazole, alone or in combination with oral flucytosine (5FC), in treating Candida endophthalmitis using a rabbit model. Albino rabbits were infected with an intravitreal inoculation of 1,000 CFU of susceptible Candida albicans and randomized 5 days later to receive treatment with oral fluconazole alone (80 mg/kg of body weight per day), a combination of fluconazole and 5FC (100 mg/kg/12 h), or no treatment. The treatment effect was assessed at 2 and 4 weeks after therapy by funduscopy, quantitative vitreous culture, and histopathology. Intravitreal levels of fluconazole, 2 to 24 h after the first dose, were measured to be > 10 times the MIC of the drug for C. albicans. Among rabbits treated with fluconazole for 2 weeks, 67% had a > 90% reduction in fungal load (P < 0.05) and 33% were sterile. After 4 weeks, all had a > 99% reduction in fungal load (P < 0.05) and 75% were sterile (P = 0.01). This treatment effect was unchanged 4 weeks after discontinuation of fluconazole. Among rabbits treated with fluconazole and 5FC for 2 weeks, 67% died during therapy. Among the surviving rabbits, 75% had a > 90% reduction in fungal load (P < 0.05) and 25% were sterile. We conclude that oral fluconazole may be useful for treatment of Candida endophthalmitis. Addition of 5FC was associated with high toxicity and minimal additional antifungal effect in our rabbit model.

Effects of antifungal therapy on inflammation, sterilization, and histology in experimental Candida albicans meningitis

To assess the effects of antifungal therapy on the course of Candida albicans central nervous system infection and inflammation, we inoculated intracisternally 10(5) CFU of C. albicans into rabbits. Fluconazole (10 mg/kg of body weight) or amphotericin B (1 mg/kg) was infused intravenously daily for 14 days. Treatment was initiated 24 h or 5 days after infection. Cerebrospinal fluid (CSF) was repeatedly obtained to culture the organisms, assess the level of inflammation, and measure drug concentrations. Brain tissue was obtained at the end of therapy for culture, drug concentration determinations, and histopathology. The median number of days of treatment required to sterilize CSF cultures was 4 days for fluconazole therapy and 1 day for amphotericin B therapy (P = 0.037). There was a significant reduction in tumor necrosis factor alpha and leukocyte concentrations in the CSF of animals treated early versus those in untreated control animals (P < 0.05 and P < 0.001, respectively; analysis of variance). Compared with treated animals, a higher proportion of cultured CSF samples from untreated animals were positive for Candida (P < 0.001). A cultured brain sample from 1 of the 12 animals treated early with amphotericin B was positive for C. albicans (P < 0.01 versus controls); cultures of brain samples from 3 of 12 animals treated early with fluconazole were positive, whereas cultures of brain samples from 10 of 12 controls were positive (P < 0.05). The mean density of C. albicans was lower in the single culture-positive amphotericin B recipient (1 x 10(1) CFU/g of brain tissue) than in those treated with fluconazole (1 x 10(3) CFU/g) and in controls (8 x 10(4) CFU/g). In animals treated late, the density of C. albicans in the brain in relation to the number of days of therapy was significantly lower in amphotericin B recipients than in those treated with fluconazole (P < 0.01) and untreated controls (P < 0.01; analysis of covariance). By histopathology, a larger proportion of untreated animals compared with those treated early demonstrated features of severe infection such as perivasculitis, ventriculitis, and evidence of fungal organisms. Compared with amphotericin B-treated rabbits, those given fluconazole had a trend toward more severe pathologic lesions. Reduced susceptibility to both fluconazole and amphotericin B was observed in the C. albicans organisms isolated from the brain of one fluconazole-treated animal. These data suggest that amphotericin B is the preferred treatment for C. albicans infections of the central nervous system.

Fluconazole in the management of endophthalmitis in disseminated candidosis of heroin addicts

Seven heroin addicts were treated with fluconazole for endophthalmitis. All the patients had cutaneous lesions: deep-seated scalp nodules and/or pustulosis in hairy zones. One patient had an abscess at the venipuncture site. Candida albicans was isolated from all the extraocular sites in all the patients. Five patients were treated with 400 mg of intravenous fluconazole on the first day, followed by 200 mg (i.v.) for one week and finally 200 mg daily orally for a further two weeks. Two patients were treated exclusively with oral fluconazole (400 mg on the first day, followed by 200 mg daily for three consecutive weeks). Tolerance to fluconazole was good and it was not necessary to stop treatment for any patient. All the cutaneous lesions stabilized and healed. The eye lesions cleared completely in all cases, except in one patient in whom vitrectomy was indicated, and in whom there was a poor response to the exclusive treatment with fluconazole and associated corticosteroids.

Candida endophthalmitis associated with intraocular lens implantation: efficacy of fluconazole therapy

Four patients with Candida parapsilosis endophthalmitis following intraocular lens implantation were treated with oral fluconazole. All had failed prior therapy with intravitreal amphotericin B. The only patient who had the lens implant removed was cured after treatment with fluconazole for one year. Three patients who did not have the lens implant removed had resolution of symptoms and return of visual acuity towards normal during the year they were on fluconazole. However, five months after therapy had been stopped, all three had decreasing visual acuity, and in two, culture of vitreous fluid yielded C. parapsilosis. Fluconazole may be effective for treatment of endophthalmitis associated with an intraocular lens implant, but only when the implant is removed also.

The use of fluconazole prophylaxis in patients with chemotherapy-induced neutropenia

Systemic Candida infections are a major cause of infectious morbidity and mortality during chemotherapy-induced neutropenia. Because of the unreliability of conventional diagnostic tests to detect systemic infection early in its course, treatment of established disseminated Candida infection has been generally disappointing with mortality rates of 60-80% in leukemia and bone marrow transplant patients and 30-40% in solid tumor patients. The use of empiric amphotericin B in patients with fever not responding to empiric antibacterial agents has been shown to be successful in reducing morbidity and mortality from fungal infections. However, its toxicity has mitigated the success of this approach. Fluconazole given prophylactically at the institution of chemotherapy has been shown to be a safe and effective alternative. It, however, is not active against all fungal species, especially Aspergillus and some of the less virulent Candida species. Some centers have reported break-through infections by these less susceptible organisms. Whether or not these limitations in its spectrum of activity will limit its usefulness in the future remains unanswered at this time and could pose a cloud to an otherwise bright promise.

Synergistic interaction of miconazole and fluconazole at sub-MIC level on Candida albicans

The in vitro combination effect of two azole antimycotics, miconazole and fluconazole, against Candida albicans was studied. When minimum (MIC) and sub-minimum (sub-MIC) inhibitory concentration and fractional inhibitory concentration (FIC) determinations were made, a synergistic interaction of the two agents at the concentration well below their individual MICs (at sub-MIC levels) was evidenced. The FIC index values ranged from 0.3 to 1.0 and the synergy was characterized by the potentiation of fluconazole activity with miconazole. The synergistic effect was also confirmed by a turbidometric method. On the other hand, such a synergistic effect against Candida krusei was not confirmed.

Synergistic postantifungal effect of flucytosine and fluconazole on Candida albicans

The in vitro efficacy of flucytosine and fluconazole, separately and in combination, with respect to induction of a postantifungal effect (PAFE) on Candida albicans was studied. PAFE refers to the persistent suppression of fungal cell growth following a short period of exposure to an antifungal agent. A turbidometric method was used to measure cell growth and to quantitate the PAFE following exposure of C. albicans yeast cells to different concentrations of the two agents for 2 h. The PAFE was determined by the difference in time (h) required for growth of the control and test cultures to increase to the 0.5 absorbance level following removal of the drug by dilution. Minimum (MIC) and fractional inhibitory concentration determinations were made and the data used for selecting the concentrations used in the PAFE evaluations. A synergistic interaction of the two drugs at concentrations well below their individual MICs was evidenced. Flucytosine:fluconazole ratios of 1:16-1:32 at concentrations ranging from 0.024-0.098 micrograms ml-1 and from 0.78-1.56 micrograms ml-1, with flucytosine and fluconazole, respectively, induced PAFEs which persisted for 2.5 h longer than those achieved when each of the two agents was assayed separately.

Comparison of fluconazole and amphotericin B for prevention and treatment of experimental Candida endocarditis

Fluconazole and amphotericin B were compared in the prophylaxis and treatment of Candida albicans aortic endocarditis in a rabbit model. In the prophylaxis study, catheterized rabbits received, prior to intravenous (i.v.) challenge with C. albicans (2 x 10(7) blastospores), either no therapy, single-dose i.v. amphotericin B (1 mg/kg of body weight), single-dose fluconazole (50 mg/kg or 100 mg/kg i.v. or intraperitoneally [i.p.]), or fluconazole (50 mg/kg or 100 mg/kg i.v. or i.p.) with a second dose 24 h after inoculation. A single dose of amphotericin B was significantly more effective than either the one- or two-dose regimens of fluconazole at both 50 mg/kg (P less than 0.001 and P less than 0.03, respectively) and 100 mg/kg (P less than 0.01 and P less than 0.001, respectively) in the prevention of C. albicans endocarditis. In parallel treatment studies of established C. albicans endocarditis, i.v. amphotericin B (1 mg/kg) or i.p. fluconazole (50 mg/kg) was begun 24 or 60 h postinfection and continued daily for 9 or 12 days. At these dose regimens, amphotericin B was consistently more effective than fluconazole in reducing fungal vegetation densities, regardless of the timing of initiation of therapy. We also examined the efficacy of fluconazole at a daily dose of 100 mg/kg i.p. administered for 21 days in the treatment of established C. albicans endocarditis. When therapy was continued for 2 weeks or longer, fluconazole was more effective than no drug and approximately twice as effective as 12 days of amphotericin B in reducing intravegetation fungal densities. Our results suggest that amphotericin B is superior to fluconazole in both the prophylaxis and treatment of C. albicans endocarditis in the rabbit model. These findings may relate to the predominantly fungistatic activity of fluconazole against C. albicans in vitro.

In vitro comparative evaluations of the postantifungal effect: synergistic interaction between flucytosine and fluconazole against Candida albicans

In vitro comparative evaluations were performed to study the efficacy of combinations of flucytosine and fluconazole in producing a postantifungal effect (PAFE) on Candida albicans. Initial studies were done to determine MIC, FIC (fractional inhibitory concentration) and optimal PAFE parameters. A turbidometric method was used to measure yeast cell growth following exposure to different concentrations of the two drugs for periods of 0.5, 1 or 2 h at temperatures of 30 degrees C and 37 degrees C. The PAFE was determined by the difference in time (h) required for growth of the control and test cultures to reach the 0.5 absorbance level following removal of the drug by dilution. Ten strains of C. albicans were then assayed (30 degrees C; 2 h exposure time) and a synergistic PAFE was evidenced with the two drugs at concentrations well below their individual MICs. PAFEs ranging from 3.8 to 10.5 h, which persisted for 1.2-2.5 h longer than those achieved with either agent separately, were evidenced when flucytosine and fluconazole were combined (flucytosine: fluconazole ratios of 1:16-1:32) at concentrations ranging from 0.024 to 0.098 micrograms ml-1 and 0.78 to 1.56 micrograms ml-1 respectively. The concentrations of each agent required to produce an optimal PAFE varied according to the C. albicans strain being assayed.