Interactions between triazoles and amphotericin B against Cryptococcus neoformans

CAF to the Rescue! Potential and Challenges of Combination Antifungal Therapy for Reducing Morbidity and Mortality in Hospitalized Patients With Serious Fungal Infections

The global burden of invasive fungal disease is substantial and escalating. Combination antifungal therapy (CAF) may improve patient outcomes by reducing development of resistance, improving drug penetration and rate of fungal clearance, and allowing for lower and less toxic antifungal drug doses; yet, increased cost, antagonism, drug-drug interactions, and toxicity are concerns. Clinical practice guidelines recommend antifungal monotherapy, rather than CAF, for most invasive fungal diseases due to a lack of comparative randomized clinical trials. An examination of the existing body of CAF research should frame new hypotheses and determine priorities for future CAF clinical trials. We performed a systematic review of CAF clinical studies for invasive candidiasis, cryptococcosis, invasive aspergillosis, and mucormycosis. Additionally, we summarized findings from animal models of CAF and assessed laboratory methods available to evaluate CAF efficacy. Future CAF trials should be prioritized according to animal models showing improved survival and observational clinical data supporting efficacy and safety.

In vitro combination with doxycycline plus antifungals against clinical Mucorales pathogens

PURPOSE

Since systematic antifungals for mucormycosis showed variable MICs depending on strains, effective and safe antifungal therapy was still needed. This study is aimed to evaluate the in vitro activity of doxycycline combined with antifungal therapy against dominant Mucorales pathogens.

METHODS

Multidrug susceptibility testing was performed with doxycycline and antifungals, including itraconazole, posaconazole, and amphotericin, in 21 isolates of 8 dominant Mucorales pathogens.

RESULTS

The fractional inhibitory concentration index according to M38 showed one Rhizopus arrhizus isolate synergic (∑FICI = 0.375) and other isolates in addition (0.5 < ∑FICI < 4).

CONCLUSIONS

Doxycycline was found to have in vitro advantages in combined antifungal treatment over antifungals alone.

In Vitro Activity of Isavuconazole and Amphotericin B in Association against Mucorales

Mucormycoses can be treated with the combination of Amphotericin B and Isavuconazole. This study evaluates the effects of these drugs in vitro against 59 strains representing 12 Mucorales. In vitro testing of the two drugs together and alone was performed using the MIC Test strip "Epsilon test synergy-method" (ETSM), which is more standard in clinical practice than microbroth dilution testing. Amphotericin B and Isavuconazole have synergistic/additive effects against L. corymbifera, R. arrhizus and M. circinelloides. Different effects have been shown for other Mucorales. ETSM can help the clinical management of mucormycosis from a practical point of view, due to its feasibility in the laboratory.

In Silico Structural Modeling and Analysis of Interactions of Tremellomycetes Cytochrome P450 Monooxygenases CYP51s with Substrates and Azoles

Cytochrome P450 monooxygenase CYP51 (sterol 14α-demethylase) is a well-known target of the azole drug fluconazole for treating cryptococcosis, a life-threatening fungal infection in immune-compromised patients in poor countries. Studies indicate that mutations in CYP51 confer fluconazole resistance on cryptococcal species. Despite the importance of CYP51 in these species, few studies on the structural analysis of CYP51 and its interactions with different azole drugs have been reported. We therefore performed in silico structural analysis of 11 CYP51s from cryptococcal species and other Tremellomycetes. Interactions of 11 CYP51s with nine ligands (three substrates and six azoles) performed by Rosetta docking using 10,000 combinations for each of the CYP51-ligand complex (11 CYP51s × 9 ligands = 99 complexes) and hierarchical agglomerative clustering were used for selecting the complexes. A web application for visualization of CYP51s' interactions with ligands was developed (http://bioshell.pl/azoledocking/). The study results indicated that Tremellomycetes CYP51s have a high preference for itraconazole, corroborating the in vitro effectiveness of itraconazole compared to fluconazole. Amino acids interacting with different ligands were found to be conserved across CYP51s, indicating that the procedure employed in this study is accurate and can be automated for studying P450-ligand interactions to cater for the growing number of P450s.

Techniques for the Assessment of In Vitro and In Vivo Antifungal Combinations

Systemic fungal infections are associated with high mortality rates despite adequate treatment. Moreover, acquired resistance to antifungals is increasing, which further complicates the therapeutic management. One strategy to overcome antifungal resistance is to use antifungal combinations. In vitro, several techniques are used to assess drug interactions, such as the broth microdilution checkerboard, agar-diffusion methods, and time-kill curves. Currently, the most widely used technique is the checkerboard method. The aim of all these techniques is to determine if the interaction between antifungal agents is synergistic, indifferent, or antagonistic. However, the interpretation of the results remains difficult. Several methods of analysis can be used, based on different theories. The most commonly used method is the calculation of the fractional inhibitory concentration index. Determination of the usefulness of combination treatments in patients needs well-conducted clinical trials, which are difficult. It is therefore important to study antifungal combinations in vivo, in experimental animal models of fungal infections. Although mammalian models have mostly been used, new alternative animal models in invertebrates look promising. To evaluate the antifungal efficacy, the most commonly used criteria are the mortality rate and the fungal load in the target organs.

Molecular epidemiology and antifungal susceptibility profiles of clinical Cryptococcus neoformans/Cryptococcus gattii species complex

Introduction. Limited data regarding the epidemiology and susceptibility profiles of cryptococcosis are available in the Middle East.Aim. Our study aimed to evaluate the molecular diversity, mating types and antifungal susceptibility pattern of Cryptococcus species (n=14) isolated from 320 suspected patients with cryptococcosis.Methodology. The URA5 gene was subjected to restriction fragment length polymorphism and sequence analysis. In addition, in vitro antifungal susceptibility testing was performed by Clinical and Laboratory Standards Institute (CLSI) M27-A4 and M59 guidelines.Results. Overall, 14 (4.4 %) patients were confirmed as cryptococcosis. Based on molecular type, 85.7 and 14.3 % of the isolates were C. neoformans VN I and VN II, respectively. Phylogenetic analysis of URA5 gene sequences revealed clustering of VN I and VN II isolates into two distinct clades with a substantial difference within each molecular type. Voriconazole and 5-fluorocytosine, respectively, had the lowest (0.031 μg ml^-1) and highest (8 µg ml^-1) MICs. The epidemiological cutoff values (ECVs) for amphotericin B, fluconazole, voriconazole and 5-fluorocytosine encompassed ≥97 % of all 14 C. neoformans VN I species. However, according to the CLSI document M59, ECVs for itraconazole (7; 50 % of the isolates) and for posaconazole (1; 7.1 % of the isolate), were one log2 dilution higher than the wild type range. Combinations of amphotericin B with 5-fluorocytosine, amphotericin B with fluconazole and fluconazole with 5-fluorocytosine exhibited synergistic effects against 37, 31 and 12.5 % of the isolates, respectively.Conclusion. Our findings may significantly contribute to the development of management strategies for patients at a higher risk of cryptococcosis, particularly HIV-positive individuals.

Dectin-2-Targeted Antifungal Liposomes Exhibit Enhanced Efficacy

Invasive fungal diseases caused by Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus have mortality rates ranging from 10 to 95%. Individual patient costs may exceed $100,000 in the United States. All antifungals in current use have serious limitations due to host toxicity and/or insufficient fungal cell killing that results in recurrent infections. Few new antifungal drugs have been introduced in the last 2 decades. Hence, there is a critical need for improved antifungal therapeutics. By targeting antifungal-loaded liposomes to α-mannans in the extracellular matrices secreted by these fungi, we dramatically reduced the effective dose of drug. Dectin-2-coated liposomes loaded with amphotericin B bound 50- to 150-fold more strongly to C. albicans, C. neoformans, and A. fumigatus than untargeted liposomes and killed these fungi more than an order of magnitude more efficiently. Targeting drug-loaded liposomes specifically to fungal cells has the potential to greatly enhance the efficacy of most antifungal drugs.

Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus cause life-threatening candidiasis, cryptococcosis, and aspergillosis, resulting in several hundred thousand deaths annually. The patients at the greatest risk of developing these life-threatening invasive fungal infections have weakened immune systems. The vulnerable population is increasing due to rising numbers of immunocompromised individuals as a result of HIV infection or immunosuppressed individuals receiving anticancer therapies and/or stem cell or organ transplants. While patients are treated with antifungals such as amphotericin B, all antifungals have serious limitations due to lack of sufficient fungicidal effect and/or host toxicity. Even with treatment, 1-year survival rates are low. We explored methods of increasing drug effectiveness by designing fungicide-loaded liposomes specifically targeted to fungal cells. Most pathogenic fungi are encased in cell walls and exopolysaccharide matrices rich in mannans. Dectin-2 is a mammalian innate immune membrane receptor that binds as a dimer to mannans and signals fungal infection. We coated amphotericin-loaded liposomes with monomers of Dectin-2’s mannan-binding domain, sDectin-2. sDectin monomers were free to float in the lipid membrane and form dimers that bind mannan substrates. sDectin-2-coated liposomes bound orders of magnitude more efficiently to the extracellular matrices of several developmental stages of C. albicans, C. neoformans, and A. fumigatus than untargeted control liposomes. Dectin-2-coated amphotericin B-loaded liposomes reduced the growth and viability of all three species more than an order of magnitude more efficiently than untargeted control liposomes and dramatically decreased the effective dose. Future efforts focus on examining pan-antifungal targeted liposomal drugs in animal models of fungal diseases.

IMPORTANCE Invasive fungal diseases caused by Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus have mortality rates ranging from 10 to 95%. Individual patient costs may exceed $100,000 in the United States. All antifungals in current use have serious limitations due to host toxicity and/or insufficient fungal cell killing that results in recurrent infections. Few new antifungal drugs have been introduced in the last 2 decades. Hence, there is a critical need for improved antifungal therapeutics. By targeting antifungal-loaded liposomes to α-mannans in the extracellular matrices secreted by these fungi, we dramatically reduced the effective dose of drug. Dectin-2-coated liposomes loaded with amphotericin B bound 50- to 150-fold more strongly to C. albicans, C. neoformans, and A. fumigatus than untargeted liposomes and killed these fungi more than an order of magnitude more efficiently. Targeting drug-loaded liposomes specifically to fungal cells has the potential to greatly enhance the efficacy of most antifungal drugs.

Fluconazole plus flucytosine is a good alternative therapy for non-HIV and non-transplant-associated cryptococcal meningitis: A retrospective cohort study

Cryptococcal meningitis (CM) carries a high risk of mortality with increasing incidences in immune competent hosts. Current treatments are not well tolerated, and evaluation of other treatments is needed. Fluconazole and 5‐flucytosine in treating immune competent hosts have not been characterised. To evaluate the efficacy of fluconazole and 5‐flucytosine in treating non‐HIV‐ and non‐transplant‐associated CM. We performed a retrospective cohort study of the outcomes in immune competent patients with CM treated with fluconazole and 5‐flucytosine or deoxycholate‐amphotericin B and 5‐flucytosine. The primary outcome was treatment response evaluated at the 12th week after initiation of antifungal therapy. A total of 43 and 47 patients received amphotericin B deoxycholate and 5‐flucytosine or fluconazole and 5‐flucytosine, respectively. A total of 38 (88.4%) patients cannot tolerate recommended doses of amphotericin B deoxycholate and 5‐flucytosine (patients needed dose reduction during the treatment). Patients given fluconazole and 5‐flucytosine had higher baseline cryptococcal burdens (median 3632 versus 900 cryptococci/mL, P = 0.008). No significant differences were seen in cryptococcus clearance (74.4% vs 70.2%, P = 0.814), treatment time (39 days, 20‐69 days vs 21 days, 7‐63 days, P = 0.107) and successful response (including complete and partial responses) rates (69.7% vs 72.3%, P = 0.820). Fluconazole and 5‐flucytosine treatment had lower total adverse events (19.1% vs 90.7%, P < 0.001). Fluconazole and 5‐flucytosine had relatively high efficacy with few adverse events in treating CM. Fluconazole and 5‐flucytosine therapy is promising in patients that do not tolerate or are not suited for amphotericin B deoxycholate treatment.

Candida Infections and Therapeutic Strategies: Mechanisms of Action for Traditional and Alternative Agents

The Candida genus comprises opportunistic fungi that can become pathogenic when the immune system of the host fails. Candida albicans is the most important and prevalent species. Polyenes, fluoropyrimidines, echinocandins, and azoles are used as commercial antifungal agents to treat candidiasis. However, the presence of intrinsic and developed resistance against azole antifungals has been extensively documented among several Candida species. The advent of original and re-emergence of classical fungal diseases have occurred as a consequence of the development of the antifungal resistance phenomenon. In this way, the development of new satisfactory therapy for fungal diseases persists as a major challenge of present-day medicine. The design of original drugs from traditional medicines provides new promises in the modern clinic. The urgent need includes the development of alternative drugs that are more efficient and tolerant than those traditional already in use. The identification of new substances with potential antifungal effect at low concentrations or in combination is also a possibility. The present review briefly examines the infections caused by Candida species and focuses on the mechanisms of action associated with the traditional agents used to treat those infections, as well as the current understanding of the molecular basis of resistance development in these fungal species. In addition, this review describes some of the promising alternative molecules and/or substances that could be used as anticandidal agents, their mechanisms of action, and their use in combination with traditional drugs.

Modulatory effect of voriconazole on the production of proinflammatory cytokines in experimental cryptococcosis in mice with severe combined immunodeficiency

Cryptococcosis is a subacute or chronic disease. For many years, amphotericin B has been used in severe fungal infections. Voriconazole is a triazole with high bioavailability, a large distribution volume, and excellent penetration of the central nervous system (CNS). The objective of this study was to evaluate the production of pro-inflammatory cytokines in the lungs during an experimental infection caused by C. neoformans in murine model (SCID) that was treated with amphotericin B and voriconazole. After intravenous inoculation with 3.0×10⁵ viable yeast cells, the animals were treated with amphotericin B and voriconazole. The daily treatments began 24hours after inoculation and lasted 15 days. We evaluated the survival curve and we measured the levels of TNF-α, IL-6 and IL-10. For all treatments, there was a significant increase in survival compared to the untreated group of animals and the group treated with voriconazole (maximum concentration). The levels of pro-inflammatory cytokines were significantly lower in the groups treated with voriconazole (maximum concentration) and amphotericin B (minimum concentration). Under the conditions studied, we can suggest by that the production of pro-inflammatory cytokines mediated by amphotericin B and voriconazole is dependent on the concentration administered.

Combining two antifungal agents does not enhance survival of Galleria mellonella larvae infected with Madurella mycetomatis

OBJECTIVE

To determine whether combination therapy would improve therapeutic outcome in eumycetoma caused by Madurella mycetomatis.

METHODS

Survival, colony-forming units (CFU), melanisation and histopathology in M. mycetomatis-infected Galleria mellonella larvae treated with amphotericin B, itraconazole, terbinafine or combinations thereof were determined.

RESULTS

Compared to larvae treated with 5% glucose, enhanced survival was obtained when M. mycetomatis-infected larvae were treated with amphotericin B, but not when they were treated with itraconazole or terbinafine. Combination therapy did not increase survival compared to 5% glucose-treated larvae, itraconazole-treated larvae or terbinafine-treated larvae. Compared to amphotericin B monotreatment, a significant decrease in survival was noted when this therapy was combined with either itraconazole or terbinafine. CFU, melanisation and histopathology did not differ between monotherapy, combination therapy or 5% glucose-treated larvae.

CONCLUSIONS

Combining different classes of antifungal agents did not enhance the survival of M. mycetomatis-infected G. mellonella larvae. Instead of improving the therapeutic outcome, combining either itraconazole or terbinafine with amphotericin B resulted in significantly lower survival rates of infected larvae than amphotericin B monotherapy. This experimental study does not provide support for the use of combined amphotericin B and itraconazole, combined itraconazole and terbinafine or combined terbinafine and amphotericin B and should be confirmed in other animal models.

Antifungal Therapy: New Advances in the Understanding and Treatment of Mycosis

The high rates of morbidity and mortality caused by fungal infections are associated with the current limited antifungal arsenal and the high toxicity of the compounds. Additionally, identifying novel drug targets is challenging because there are many similarities between fungal and human cells. The most common antifungal targets include fungal RNA synthesis and cell wall and membrane components, though new antifungal targets are being investigated. Nonetheless, fungi have developed resistance mechanisms, such as overexpression of efflux pump proteins and biofilm formation, emphasizing the importance of understanding these mechanisms. To address these problems, different approaches to preventing and treating fungal diseases are described in this review, with a focus on the resistance mechanisms of fungi, with the goal of developing efficient strategies to overcoming and preventing resistance as well as new advances in antifungal therapy. Due to the limited antifungal arsenal, researchers have sought to improve treatment via different approaches, and the synergistic effect obtained by the combination of antifungals contributes to reducing toxicity and could be an alternative for treatment. Another important issue is the development of new formulations for antifungal agents, and interest in nanoparticles as new types of carriers of antifungal drugs has increased. In addition, modifications to the chemical structures of traditional antifungals have improved their activity and pharmacokinetic parameters. Moreover, a different approach to preventing and treating fungal diseases is immunotherapy, which involves different mechanisms, such as vaccines, activation of the immune response and inducing the production of host antimicrobial molecules. Finally, the use of a mini-host has been encouraging for in vivo testing because these animal models demonstrate a good correlation with the mammalian model; they also increase the speediness of as well as facilitate the preliminary testing of new antifungal agents. In general, many years are required from discovery of a new antifungal to clinical use. However, the development of new antifungal strategies will reduce the therapeutic time and/or increase the quality of life of patients.

Combined antifungal therapy against systemic murine infections by rare Cryptococcus species

Cryptococcus albidus and Cryptococcus laurentii are uncommon species of this genus that in recent decades have increasingly caused opportunistic infections in humans, mainly in immunocompromised patients; the best therapy for such infection being unknown. Using a murine model of systemic infection by these fungi, we have evaluated the efficacy of amphotericin B (AMB) at 0.8 mg/kg, administered intravenously, fluconazole (FLC) or voriconazole (VRC), both administered orally, at 25 mg/kg and the combination of AMB plus VRC against three C. albidus and two C. laurentii strains. All the treatments significantly reduced the fungal burden in all the organs studied. The combination showed a synergistic effect in the reduction in fungal load, working better than both monotherapies. The histopathological study confirmed the efficacy of the treatments.

Posaconazole: An Update of Its Clinical Use

Posaconazole (PCZ) is a relatively new addition to the azole antifungals. It has fungicidal activities against Aspergillus fumigatus, Blastomyces dermatitidis, selected Candida species, Crytopcoccus neoformans, and Trichosporon. PCZ also has fungistatic activities against Candida, Coccidioides, selected Fusarium spp., Histoplasma, Scedosporium and Zygomycetes. In addition, combining the drug with caspofungin or amphotericin B results in a synergistic interaction against A. fumigatus, C. glabrata and C. neoformans. The absorption of PCZ suspension is enhanced when given with food, nutritional supplements, and carbonated beverages. Oral administration of PCZ in divided doses also increases its bioavailability. PCZ has a large volume of distribution and is highly protein bound (>95%). The main elimination route of PCZ is fecal. PCZ is an inhibitor of the CYP3A4 enzyme; therefore, monitoring for drug-drug interactions is warranted with other CYP3A4 substrates/inhibitors/inducers. The most common adverse effects include headache, fatigue, nausea, vomiting and elevated hepatic enzymes. PCZ, with its unique antifungal activities, expands the azole class of antifungal agents. Because of its limit in formulation, PCZ oral suspension is recommended in immunocompromised patients with functional gastrointestinaltracts who fail conventional antifungal therapies or who are suspected to have a breakthrough fungal infection. However, a delayed-release tablet formulation and intravenous (IV) injection became available in 2014, expanding the use of PCZ in other patient populations, including individuals who are unable to take oral formulations.

Comparative effectiveness of induction therapy for human immunodeficiency virus-associated cryptococcal meningitis: a network meta-analysis

Background.  Multiple international treatment guidelines recommend amphotericin-based combination regimens for induction therapy of cryptococcal meningitis. Yet, only 1 trial has reported a mortality benefit for combination amphotericin-flucytosine, and none have reported a mortality benefit for combination amphotericin-fluconazole. Methods.  We conducted a Bayesian network meta-analysis to estimate the comparative effectiveness of recommended induction therapies for HIV-associated cryptococcal meningitis. We searched PubMed and Cochrane CENTRAL for clinical reports of induction therapy for HIV-associated cryptococcal meningitis. We extracted or calculated early (two-week) and late (six to 12-week) mortality by treatment arm for the following induction regimens: amphotericin B alone, amphotericin B + flucytosine, amphotericin B + triazoles, amphotericin B + flucytosine +triazoles, triazoles alone, triazoles + flucytosine, liposomal amphotericin B, and amphotericin B + other medicines. Results.  In the overall sample (35 studies, n = 2483), we found no evidence of decreased mortality from addition of flucytosine or triazoles to amphotericin B, compared with amphotericin B alone. Although we did find a nonsignificant benefit for addition of flucytosine to amphotericin B in studies including participants with altered levels of consciousness, we did not identify a benefit for combination therapy in restricted analyses in either resource-rich or resource-limited settings, studies conducted before or after 2004, and studies restricted to a high dose of amphotericin B and fluconazole. Conclusions.  Given considerations of drug availability and toxicity, there is an important need for additional data to clarify which populations are most likely to benefit from combination therapies for human immunodeficiency virus-associated cryptococcal meningitis.

In vitro and in vivo evidence for amphotericin B as a P-glycoprotein substrate on the blood-brain barrier

Amphotericin B (AMB) has been a mainstay therapy for fungal infections of the central nervous system, but its use has been limited by its poor penetration into the brain, the mechanism of which remains unclear. In this study, we aimed to investigate the role of P-glycoprotein (P-gp) in AMB crossing the blood-brain barrier (BBB). The uptake of AMB by primary brain capillary endothelial cells in vitro was significantly enhanced after inhibition of P-gp by verapamil. The impact of two model P-gp inhibitors, verapamil and itraconazole, on brain/plasma ratios of AMB was examined in both uninfected CD-1 mice and those intracerebrally infected with Cryptococcus neoformans. In uninfected mice, the brain/plasma ratios of AMB were increased 15 min (3.5 versus 2.0; P < 0.05) and 30 min (5.2 versus 2.8; P < 0.05) after administration of verapamil or 45 min (6.0 versus 3.9; P < 0.05) and 60 min (5.4 versus 3.8; P < 0.05) after itraconazole administration. The increases in brain/plasma ratios were also observed in infected mice treated with AMB and P-gp inhibitors. The brain tissue fungal CFU in infected mice were significantly lower in AMB-plus-itraconazole or verapamil groups than in the untreated group (P < 0.005), but none of the treatments protected the mice from succumbing to the infection. In conclusion, we demonstrated that P-gp inhibitors can enhance the uptake of AMB through the BBB, suggesting that AMB is a P-gp substrate.

Simultaneous cryptococcal and tuberculous meningitis in a patient with systemic lupus erythematosus

Simultaneous central nervous system (CNS) infection with Cryptococcus and tuberculosis (TB) is very rare. Despite improved therapeutic options, treatment of CNS cryptococcosis is still difficult and needs invasive treatment modalities, such as intrathecal or intraventricular amphotericin B, in refractory cases. We describe a patient with systemic lupus erythematosus diagnosed with simultaneous cryptococcal and TB meningitis who had a poor response to intravenous liposomal amphotericin B and fluconazole, but was successfully treated with intraventricular amphotericin B, in addition to anti-TB therapy.

Susceptibility profile of clinical and environmental isolates of Cryptococcus neoformans and Cryptococcus gattii in Uberaba, Minas Gerais, Brazil

Cryptococcus neoformans and C. gattii are the etiologic agents of cryptococcosis, a life-threatening disease in both immunocompromised and immunocompetent hosts. Antifungal resistance has been evaluated using different methods, breakpoints, and sizes of test populations and it is an emerging as a significant issue worldwide. A total of 176 (95 clinical and 81 environmental) C. neoformans and eight clinical C. gattii isolates were evaluated to determine the minimal inhibitory concentration (MIC) according to the Clinical and Laboratory Standards Institute method. A total of 10.5% of the C. neoformans clinical isolates were resistant to amphotericin B (AMB), and 6.2% of the environmental isolates were resistant to fluconazole (FLZ). Environmental and clinical isolates presented epidemiologic cut-off values (ECVs) of 64 and 16 to FLZ and 1 and 2 to AMB, respectively. All of the C. gattii isolates showed high susceptibility to most drugs evaluated. Clinical isolates had lower susceptibility than environmental isolates to AMB and itraconazole whereas environmental isolates had lower susceptibility than the clinical isolates to FLZ, voriconazole, and ketoconazole. However, no difference was found in the susceptibility of the two species. The MICs and ECVs to antifungals can help to select the best therapeutic option for tracking epidemiological resistance among clinical and environmental isolates of Cryptococcus spp. around the world.

Dynamic interaction between fluconazole and amphotericin B against Cryptococcus gattii

Cryptococcus gattii is the main pathogen of cryptococcosis in healthy patients and is treated mainly with fluconazole and amphotericin B. The combination of these drugs has been questioned because the mechanisms of action could lead to a theoretical antagonistic interaction. We evaluated distinct parameters involved in the in vitro combination of fluconazole and amphotericin B against Cryptococcus gattii. Fourteen strains of C. gattii were used for the determination of MIC, fractional inhibitory concentration, time-kill curve, and postantifungal effect (PAFE). Ergosterol quantification was performed to evaluate the influence of ergosterol content on the interaction between these antifungals. Interaction between the drugs varied from synergistic to antagonistic depending on the strain and concentration tested. Increasing fluconazole levels were correlated with an antagonistic interaction. A total of 48 h was necessary for reducing the fungal viability in the presence of fluconazole, while 12 h were required for amphotericin B. When these antifungals were tested in combination, fluconazole impaired the amphotericin B activity. The ergosterol content decreased with the increase of fluconazole levels and it was correlated with the lower activity of amphotericin B. The PAFE found varied from 1 to 4 h for fluconazole and from 1 to 3 h for amphotericin B. The interaction of fluconazole and amphotericin B was concentration-dependent and special attention should be directed when these drugs are used in combination against C. gattii.

[Fungal keratitis caused by Cylindrocarpon lichenicola]

We report a case of a 67-year-old woman with no significant past ocular history, who was referred for management of an unresponsive microbial keratitis resulting from trauma with a piece of clothing fabric 1 month previously in Portugal and worsening despite topical fortified antibiotics. On examination, visual acuity was limited to "light perception". Slit lamp examination revealed an 11×11mm full-thickness corneal infiltrate. Confocal images showed branching hyphae suggestive of a fungal infection. Fungal cultures of corneal scrapings revealed growth of Cylindrocarpon lichenicola, a saprophytic, filamentous fungus, which is an unusual cause of keratitis. Despite aggressive antifungal therapy with voriconazole and amphotericin B, she required penetrating keratoplasty for impending corneal perforation. Follow-up was uneventful, with no recurrence at 1 year. Fungal infections must be suspected in all corneal ulcers of traumatic etiology. Specific cultures and confocal microscopy must be performed early, so as to enable early treatment modification.

Posaconazole: A new agent for the prevention and management of severe, refractory or invasive fungal infections

Posaconazole is the newest antifungal agent to be approved for use in Canada. With excellent in vitro activity against a broad spectrum of yeasts and filamentous fungi, as well as having a well-tolerated oral formulation, posaconazole offers many potential advantages. Of particular interest are its seemingly lower potential for cross-resistance with other azoles and its activity (unique among oral antifungal agents) against the zygomycetes. As the incidence of both common and uncommon fungal infections increases commensurate with the growing population of immunocompromised individuals, posaconazole may ultimately become an important therapeutic option. The present article reviews the in vitro and in vivo data describing its activity, and focuses on both the proven and the potential clinical applications of this new triazole agent.

Voriconazole, combined with amphotericin B, in the treatment for pulmonary cryptococcosis caused by C. neoformans (serotype A) in mice with severe combined immunodeficiency (SCID)

Cryptococcosis is a subacute or chronic systemic mycosis with a cosmopolitan nature, caused by yeast of the genus Cryptococcus neoformans. The model of systemic cryptococcosis in mice with severe combined immunodeficiency (SCID) is useful for immunological and therapeutic study of the disease in immunodeficient hosts. Amphotericin B, fluconazole and flucytosine are the drugs most commonly used to treat cryptococcosis. Voriconazole is a triazole with high bioavailability, large distribution volume, and excellent penetration of the central nervous system. The objective of this study was to evaluate treatment with amphotericin B (AMB), voriconazole (VRC), and AMB, used in combination with VRC, of experimental pulmonary cryptococcosis in a murine model (SCID). The animals were inoculated intravenously (iv) with a solution containing 3.0 × 10(5) viable cells of C. neoformans ATCC 90112, (serotype A). Treatments were performed with amphotericin B (1.5 mg/kg/day), voriconazole (40.0 mg/kg/day) and AMB (1.5 mg/kg/day) combined with VRC (40.0 mg/kg/day); began 1 day after the initial infection; were daily; and lasted 15 days. Evaluations were performed using analysis of the survival curve and isolation of yeast in the lung tissue. There was a significant increase in survival in groups treated with AMB combined with VRC, compared with the untreated group and groups receiving other treatments (P < 0.05). In the group treated only with VRC and AMB combined with VRC, there was a significant reduction (P < 0.05) in the isolation of C. neoformans in lung tissue. Amphotericin B combined with voriconazole may be an effective alternative to increasing survival and may reduce yeast in the lung tissue of mice with pulmonary cryptococcosis and SCID.

Treatment of refractory feline sporotrichosis with a combination of intralesional amphotericin B and oral itraconazole

OBJECTIVE To describe the use of intralesional amphotericin B in localised lesions for the treatment of 26 cats from Rio de Janeiro, Brazil, with sporotrichosis refractory to oral itraconazole. DESIGN Uncontrolled intervention study. METHOD The 26 cats in this study were diagnosed with sporotrichosis, confirmed by isolation of Sporothrix schenckii, and presented residual localised skin lesions refractory to treatment with oral itraconazole for a minimum period of 8 weeks. The animals received weekly applications of intralesional amphotericin B in conjunction with oral itraconazole. In cases of owner unavailability, a maximum of 2 weeks between the infiltrations was accepted. RESULTS Twenty-two (84.6%) of the 26 treated cats achieved clinical remission, 16 (72.7%) of which were cured, and in the remaining six (27.3%) the lesions recurred at the same site. Lack of clinical response was observed in one animal and three owners abandoned treatment. CONCLUSION The proposed therapeutic regimen is an adjunctive treatment option for cats with sporotrichosis presenting as residual skin lesions refractory to itraconazole.

[Disseminated papules in a patient with acute myeloid leukemia]

Cryptococcosis most commonly occurs in immunosuppressed patients. The pathogen is the yeast Cryptococcus neoformans. This article reports on the case of a 20-year-old female patient with acute myeloid leukemia who suddenly developed disseminated livid red papules and papulovesicles. The clinical picture and in particular the histopathology findings led to the diagnosis of cutaneous cryptococcosis, which was successfully treated with amphotericin B. For the differential diagnosis generalized herpes zoster, erythema exudativum multiforme and disseminated molluscum contagiosum must be considered. To confirm the diagnosis attempts can also be made to culture the pathogen from skin biopsy preparations. Furthermore, fungal spores can be rapidly and simply detected with the Tzanck test.

Intralesional amphotericin B in a cat with refractory localised sporotrichosis

The present report concerns a case of sporotrichosis in a 3-year-old male crossbred cat. After 9 months of oral itraconazole (20mg/kg) therapy, all skin lesions had resolved with the exception of a single nodular lesion located on the bridge of the nose. Therefore, a combined therapy that included intralesional (IL) amphotericin B (1mg/kg) was started. The lesion resolved completely after three weekly administrations of IL amphotericin B, given in concert with oral itraconazole. The cat remains well 1 year after discontinuing therapy, with no signs of recurrence.

Treatment of invasive fungal infections in immunocompromised and transplant patients: AmBiLoad trial and other new data

Opportunistic invasive fungal infections (IFIs) have changed. Moreover, a significantly greater therapeutic armamentarium is now available, with liposomal amphotericin B (L-AmB) administered in new ways, for example in higher doses, in combination with other compounds or inhaled. The objective of this study was to review these three aspects. The AmBiLoad study was designed to clarify whether higher doses of L-AmB could be more efficacious than the licensed dose of 3-5 mg/kg. It was a multicentric study where patients were randomised to receive a 14-day course of 3 mg/kg/day or 10 mg/kg/day L-AmB. A total of 339 patients were enrolled during the study period (April 2003 to October 2004). Discontinuation of treatment, mainly due to adverse events, was frequent (13% in the standard dose group vs. 24% in the high dose group), and only 66% and 50%, respectively, completed 14 days of randomised treatment. There was no statistically significant difference with regard to favourable overall responses between the treatment groups (50% in the standard dose group vs. 46% in the high dose group; P = 0.65). In addition, there was no significant difference according to type of IFI (invasive aspergillosis, 50% vs. 46% in the standard and high dose groups, respectively). The obvious conclusion of this study was that administration of 10 mg/kg/day L-AmB to patients with IFI does not improve efficacy but increases toxicity and price. In vitro and experimental data suggest that the combination of AmB with other antifungal agents may be more effective than monotherapy; however, data regarding the clinical efficacy of L-AmB in combination with other agents are scarce. The use of inhaled L-AmB has shown promising results for use as antifungal prophylaxis in high-risk patients.

Fungicidal versus Fungistatic: what's in a word?

BACKGROUND

Historically clinicians have preferred to use 'cidal' antifungal agents, particularly in critically ill patients. However, data to support the belief that the preferential use of a 'cidal' agent results in better patient outcomes has been lacking.

OBJECTIVE

This review examined the in vitro definitions of fungicidal and fungistatic as well as their strengths and limitations.

METHODS

A Medline search was performed in order to identify literature that examined the in vitro or in vivo impact of fungicidal and fungistatic activity. The study examined three common invasive fungal infections, namely cryptococcal meningitis, candidemia and invasive aspergillosis, where sufficient comparisons of fungicidal and fungistatic agents have been performed to allow for the evaluation of the clinical importance of these in vitro findings.

RESULTS AND CONCLUSION

A clear clinical benefit of fungicidal agents over those with fungistatic activity remains elusive. Patients with cryptococcal meningitis clearly benefit from early fungicidal therapy but require long-term suppression. The data in invasive Candida sp. infections are tantalizing and suggest that fungicidal therapy may be important. However, the data for invasive aspergillosis do not support the hypothesis that fungicidal activity improves outcomes.

Combination antifungals: an update

Invasive fungal infections are an important cause of morbidity and mortality in specific patient populations. There has been an impressive increase in the antifungal armamentarium, yet optimal therapies for many invasive fungal infections remain unknown. Genomic sequencing of a number of pathogenic fungi will pave the way to discovering additional newer targets for antifungal drug design. These new discoveries, plus the existing repertoire of antifungal agents, create the need to effectively model single and combination antifungal agents. Future therapies may also include the use of cell-stress pathway inhibitors in combination with existing antifungal agents. This review focuses on combination antifungal therapy against Cryptococcus neoformans, Candida and Aspergillus species. Combination therapy is only supported by randomized clinical trials for cryptococcal meningitis. We review data from in vitro and animal model studies as well as insights from clinical trials to discuss current thoughts and highlight the gaps in our knowledge surrounding combination antifungal therapy.

Combination antifungal therapy: what can and should we expect?

Invasive fungal infections are associated with significant morbidity and mortality among immunocompromised patients. Recent advances in antifungal development have afforded us more pharmacologic compounds to choose from when managing these fungal infections. The role of combination antifungal therapy has been well established for fungal infections such as cryptococcal meningitis. The availability of new antifungals, increased incidence of mould infections and high mortality among certain affected populations, such as hematopoietic stem cell transplant recipients, has stimulated interest in the clinical use of combination antifungal therapy. In this paper, we review supporting evidence for the use of combination antifungals in the treatment of cryptococcal meningitis, invasive candidiasis, invasive aspergillosis and zygomycosis. Several controlled clinical trials have demonstrated benefits of combination antifungal approaches for patients with cryptococcal meningitis and invasive candidiasis, but variable effects when using different agents in combination have been reported. Randomized prospective studies of combination antifungal therapy in mould infections are lacking but some series provide supportive evidence for this approach. We also describe limitations of the data and these study designs, including the fact that we still need randomized controlled multicenter studies of combination antifungal therapy for mould infections. Trials in this area should be performed with efficiency and economics in mind, and could potentially use surrogate markers as end points. Therefore, we suggest future investigations of combination antifungal therapy should include a randomized, comparative trial of primary therapy for invasive aspergillosis.

Efficacies of caspofungin and a combination of caspofungin and meropenem in the treatment of murine disseminated candidiasis

Disseminated candidiasis is relatively common in immunocompromised patients. The treatment protocol of these patients usually includes broad-spectrum antibiotics and also emprical antifungals initiated due to unresponsiveness to antibiotics. In this study the efficacies of caspofungin and meropenem - separately and together - in mice with disseminated candidiasis were studied. Immunocompetent mice were infected intravenously with 2x10(6) CFU of Candida albicans. At 24 h postinfection, intraperitoneal therapy was initiated and was continued for 7 days. Therapy groups included those given caspofungin (0.5, 1.25, 5 mg/kg/day), meropenem (20 mg/kg/day), and a combination of the two drugs. The outcome of therapy was evaluated by kidney tissue burden studies and histologic examination. In vitro, drug susceptibilities were tested by checkerboard analysis. Kidney CFU counts showed that mice that had received both drugs had lower residual burdens. Caspofungin was effective at doses of 0.5, 1.25, 5 mg/kg compared to infected untreated controls. In vitro, MICs of caspofungin and meropenem were <0.075 micro g/ml and >64 micro g/ml, respectively. Synergism was observed with the combination. Histopathology showed that the degree of inflammation was 25% less and tubular necrosis was more restricted in combined therapy than monotherapy. The results indicate that concurrent caspofungin and meropenem therapy may be beneficial.

Posaconazole: clinical pharmacology and potential for management of fungal infections

Posaconazole is a novel lipophilic antifungal triazole that inhibits cytochrome P450-dependent 14-alpha demethylase in the biosynthetic pathway of ergosterol. Inhibition of this enzyme leads to an accumulation of toxic 14-alpha methylsterols and a depletion of ergosterol, resulting in a perturbation of the function of the fungal cell membrane and blockage of cell growth and division. In vitro, posaconazole has potent and broad-spectrum activity against opportunistic, endemic and dermatophytic fungi. This activity extends to organisms that are often refractory to existing triazoles, amphotericin B or echinocandins, such as Candida glabrata, Candida krusei, Aspergillus terreus, Fusarium spp. and the Zygomycetes. A large variety of animal models of invasive fungal infections have provided consistent evidence of efficacy against these organisms in vivo, both in normal and immunocompromised animals. Posaconazole is available as an oral suspension and optimal exposure is achieved when the drug is administered in two to four divided doses along with food or a nutritional supplement. The compound has a large volume of distribution, in the order of 5 l/kg, and a half-life of approximately 20 h. Posaconazole is not metabolized to a significant extent through the cytochrome P450 enzyme system and is primarily excreted in an unchanged form in the feces. Although it is inhibitory, cytochrome P3A4 has no effect on 1A2, 2C8, 2C9, 2D6 and 2E1 isoenzymes, and therefore, a limited spectrum of drug-drug interactions can be expected. Pharmacokinetic studies in special populations revealed no necessity for dosage adjustment based on differences in age, gender, race, renal or hepatic function. Posaconazole has demonstrated strong antifungal efficacy in Phase II and III clinical trials in immunocompromised patients with oropharyngeal and esophageal candidiasis. Posaconazole also showed promising efficacy as salvage therapy in a large Phase II study including 330 patients with invasive fungal infections intolerant to or refractory to standard therapies. Posaconazole appears to be well tolerated in a manner comparable with that of fluconazole and it is currently under regulatory review in the USA and Europe for the treatment of refractory invasive fungal infections. This drug profile reviews the preclinical and clinical pharmacology of posaconazole and its potential role for prevention and treatment of invasive fungal infections.

Interaction between posaconazole and caspofungin in concomitant treatment of mice with systemic Aspergillus infection

The interaction of posaconazole and caspofungin was evaluated in concomitant treatment of Aspergillus fumigatus (two strains) or A. flavus (one strain) systemic infections in immunocompetent mice. Survival curves for mice treated with the combinations were compared statistically with those for mice treated with the component monotherapies. No antagonism was observed.

Role of AFR1, an ABC transporter-encoding gene, in the in vivo response to fluconazole and virulence of Cryptococcus neoformans

We have recently demonstrated that upregulation of the ATP binding cassette (ABC) transporter-encoding gene AFR1 in Cryptococcus neoformans is involved in the in vitro resistance to fluconazole of this yeast. In the present study, we investigated the role of AFR1 in the in vivo response to fluconazole in a mouse model of systemic cryptococcosis. Mice were infected with a wild-type fluconazole-susceptible strain of C. neoformans, strain BPY22; an afr1 mutant, BPY444, which displayed hypersusceptibility to fluconazole in vitro; or an AFR1-overexpressing strain, BPY445, which exhibited in vitro resistance to the drug. In each of the three groups, infected animals were randomly assigned to fluconazole treatment or untreated-control subgroups. As expected, fluconazole prolonged survival and reduced fungal tissue burdens (compared with no treatment) in BPY22- and BPY444-infected mice, whereas it had no significant effects in mice infected with BPY445. When the pathogenicities of these strains in mice were investigated, strain BPY445 was significantly more virulent than BPY22 following inhalational or intravenous inoculation, but mice infected with BPY444 survived significantly longer than BPY22-infected animals only when infection was acquired via the respiratory tract. In in vitro macrophage infection studies, strain BPY445 also displayed enhanced intracellular survival compared with strains BPY22 and BPY444, suggesting that its increased virulence may be due to its reduced vulnerability to the antimicrobial factors produced by phagocytic cells. These findings indicate that the upregulation of the AFR1 gene is an important factor in either determining the in vivo resistance to fluconazole or influencing the virulence of C. neoformans.

Combination therapy with terbinafine and amphotericin B in a rabbit model of experimental invasive aspergillosis

Antagonistic effects of combination therapy using amphotericin B (AmB) with agents which block ergosterol synthesis are a concern. Terbinafine was evaluated with AmB to assess antagonism or synergy in a rabbit model of invasive aspergillosis. Terbinafine had relatively little activity but did not demonstrate antagonism against AmB in our model.

Antifungal combination therapy: clinical potential

Combination antifungal therapy has been an area of research and clinical interest since systemic antifungals became available decades ago. In vitro and clinical data were generated for some of the more common invasive fungal infections, especially candidiasis, but until very recently few clinical studies were performed. The first invasive fungal infection to be examined in clinical trials with adequate statistical power was cryptococcal meningitis and several of these trials stand out as classical studies in the clinical evaluation of combination antifungal therapy. More recently, since the availability of the newer antifungal agents, including the echinocandins and extended-spectrum triazoles, there has been a growing interest in examining combination antifungal therapy for invasive fungal disease, especially invasive aspergillosis. This is by no means a comprehensive review of all existing experimental data. Instead, the focus is on the clinical data that have been generated to date and on providing insights into potential future clinical directions. For instance, recent clinical data for cryptococcosis confirm that amphotericin B plus flucytosine is the most active combination for patients with cryptococcal meningitis. A recently completed clinical trial in candidaemia suggests a trend towards improved outcomes among patients receiving amphotericin B plus fluconazole versus fluconazole alone. In aspergillosis, several experimental models suggest benefit of a variety of antifungal combinations, but have not been confirmed in prospective clinical trials. Ultimately, the goal is to provide the reader with a comprehensive but useful review to this complicated and often confusing therapeutic dilemma.

Identification of a novel antifungal nonapeptide generated by combinatorial approach

It is becoming clear that antimicrobial peptides are important components of the innate defences of all species of life. They kill very rapidly, do not easily select resistant mutants and are synergistic with potentially toxic conventional therapeutic agents against microbes. This paper describes an attempt to expand a lead hexapeptide motif synthesized through combinatorial approach. A cationic peptide H-Arg-Trp-Trp-Arg-D-Trp-D-Phe-Ile-D-Phe-His-NH2 was found to be active with a therapeutic index of >17. I was proposed that the combination of peptide with known antifungal agents may identify synergistic combinations that would ideally reduce the dosage of conventional antifungals as well as their associated toxicity. Nine different pathogenic strains and species of Candida and two of Cryptococcus neoformans were employed in chequerboard method and in time kill assays to evaluate the synergistic effect of the lead peptide in combination with amphotericin B, 5-flucytosine, ketoconazole and fluconazole. We found synergistic interaction between the peptide and all four drugs against Cryptococcus isolates whilst both synergistic and additive combinations occurred when Candida isolates were used.

Interaction between posaconazole and amphotericin B in concomitant treatment against Candida albicans in vivo

The interaction of posaconazole and amphotericin B was evaluated in concomitant treatment of Candida albicans systemic infections in immunocompetent mice by using four strains of C. albicans with different susceptibilities to fluconazole. Posaconazole and amphotericin B were each tested at four dose levels alone and in all possible combinations against each C. albicans strain. Survival curves of mice treated with combinations of posaconazole and amphotericin B were statistically compared with those of mice treated with the component monotherapies. Of the 64 total combinations evaluated against the C. albicans strains (16 combinations per strain), 20.3% were more effective in prolonging mouse survival than both of the monotherapies, 45.3% were more effective than one of the monotherapies, and 32.8% were similar to both monotherapies. No evidence of antagonism was observed between posaconazole and amphotericin B in this mouse model, consistent with in vitro results against the same strains.

Combination treatment of invasive fungal infections

The persistence of high morbidity and mortality from systemic fungal infections despite the availability of novel antifungals points to the need for effective treatment strategies. Treatment of invasive fungal infections is often hampered by drug toxicity, tolerability, and specificity issues, and added complications often arise due to the lack of diagnostic tests and to treatment complexities. Combination therapy has been suggested as a possible approach to improve treatment outcome. In this article, we undertake a historical review of studies of combination therapy and also focus on recent studies involving newly approved antifungal agents. The limitations surrounding antifungal combinations include nonuniform interpretation criteria, inability to predict the likelihood of clinical success, strain variability, and variations in pharmacodynamic/pharmacokinetic properties of antifungals used in combination. The issue of antagonism between polyenes and azoles is beginning to be addressed, but data regarding other drug combinations are not adequate for us to draw definite conclusions. However, recent data have identified potentially useful combinations. Standardization of assay methods and adoption of common interpretive criteria are essential to avoid discrepancies between different in vitro studies. Larger clinical trials are needed to assess whether combination therapy improves survival and treatment outcome in the most seriously debilitated patients afflicted with life-threatening fungal infections.

Evaluation of Mycograb®, amphotericin B, caspofungin, and fluconazole in combination against Cryptococcus neoformans by checkerboard and time-kill methodologies

This article reported the identification of heat shock protein 90 (hsp90) homologues by immunoblot in Cryptococcus neoformans. Mycograb, a genetically recombinant antibody against hsp90, was evaluated against 8 clinical isolates and the National External Quality Assessment Service for Microbiology strain of C. neoformans alone and in combination with amphotericin B, caspofungin, and fluconazole by checkerboard assay. At the end point of an optically clear well, the minimum inhibitory concentration (MIC) 0's ranged from 256 to 1024 microg/mL for Mycograb, from 0.5 to 1 microg/mL for amphotericin B, and from 16 to 32 microg/mL for caspofungin. The combination of Mycograb and amphotericin B produced a fractional inhibitory concentration index from 0.27 to 0.56, indicating a mainly synergistic effect, whereas for caspofungin, it varied from 0.5 to 2. At an end point of > or =50% inhibition, the MIC-2s varied from 16 to 128 microg/mL for Mycograb and from 0.125 to 16 microg/mL for fluconazole. The fractional inhibitory concentration index classified the combination as indifferent for 5 isolates, additive for 3 more isolates, and synergistic in a single isolate. Time-kill analysis on 2 isolates (F/7844 and F/10156), which had synergistic and additive results with amphotericin B, respectively, on checkerboard was performed with 4-16 microg/mL of Mycograb, 2-8 microg/mL of fluconazole, and 0.0625-2 microg/mL of amphotericin B. This demonstrated an increasingly static effect with augmenting concentrations of fluconazole and an initial static effect with amphotericin B at lower concentrations, which became fungicidal as the level of drug increased. The addition of either 4 or 8 microg/mL of Mycograb to 0.5 microg/mL of amphotericin B with C. neoformans F/7844 changed a static effect to a fungicidal effect at 8 h with an increased killing of 1.2 logs at 48 h. With C. neoformans F/10156, the addition of 16 microg/mL of Mycograb to 0.25 microg/mL of amphotericin B produced a difference in killing from 1 logarithm after 4 h to 1.5 logarithms after 48 h. These data suggest that the combination of amphotericin B and Mycograb would be worth exploring in the treatment of infection due to C. neoformans.

In vitro activities of voriconazole in combination with three other antifungal agents against Candida glabrata

Candida glabrata has recently emerged as a significant pathogen involved in both superficial and deep-seated infections. In the present study, a checkerboard broth microdilution method was performed to investigate the in vitro activities of voriconazole (VOR) in combination with terbinafine (TRB), amphotericin B (AMB), and flucytosine (5FC) against 20 clinical isolates of C. glabrata. Synergy, defined as a fractional inhibitory concentration (FIC) index of < or = 0.50, was observed in 75% of VOR-TRB, 10% of VOR-AMB, and 5% of VOR-5FC interactions. None of these combinations yielded antagonistic interactions (FIC index > 4). When synergy was not achieved, there was still a decrease in the MIC of one or both drugs used in the combination. In particular, the MICs were reduced to < or = 1.0 microg/ml as a result of the combination for all isolates for which the AMB MIC at the baseline was > or = 2.0 microg/ml. By a disk diffusion assay, the halo diameters produced by antifungal agents in combination were greater that those produced by each drug alone. Finally, killing curves showed that VOR-AMB exhibited synergistic interactions, while VOR-5FC sustained fungicidal activities against C. glabrata. These studies demonstrate that the in vitro activity of VOR against this important yeast pathogen can be enhanced upon combination with other drugs that have different modes of action or that target a different step in the ergosterol pathway. Further studies are warranted to elucidate the potential beneficial effects of such combination regimens in vivo.

Posaconazole and amphotericin B combination therapy against Cryptococcus neoformans infection

To investigate the effects of posaconazole (POS) and amphotericin B (AMB) combination therapy in cryptococcal infection, we established an experimental model of systemic cryptococcosis in CD1 mice by intravenous injection of three distinct clinical isolates of Cryptococcus neoformans. Therapy was started 24 h after the infection and continued for 10 consecutive days. POS was given at 3 and 10 mg/kg of body weight/day, while AMB was given at 0.3 mg/kg/day. Combination therapy consisted of POS given at a low (combo 3) or at a high (combo 10) dose plus AMB. Survival studies showed that combo 3 was significantly more effective than POS at 3 mg/kg for two isolates tested (P value, < or = 0.001), while combo 10 was significantly more effective than POS at 10 mg/kg for all three isolates (P values ranging from <0.001 to 0.005). However, neither combination regimen was more effective than AMB alone. For two isolates, combination therapy was significantly more effective than each single drug at reducing the fungal burden in the brain (P values ranging from 0.001 to 0.015) but not in the lungs. This study demonstrates that the major impact of POS and AMB combination therapy is on brain fungal burden rather than on survival.