The 1998 Garrod lecture. Current and future antifungal therapy: new targets for antifungal agents

Distribution and hydrolytic enzyme characteristics of Candida albicans strains isolated from diabetic patients and their non-diabetic consorts

INTRODUCTION

The aim of this study was to investigate the oral colonization profile of Candida albicans strains isolated from diabetic patients and their non-diabetic consorts. In addition hydrolytic enzyme activity of these isolates was analysed.

METHODS

The genetic diversity of C. albicans oral isolates from 52 couples was established using isoenzyme marker and cluster analysis. Hydrolytic enzyme characteristics, namely secreted aspartyl proteinases (SAPs) and phospholipases (PLs) were also analysed.

RESULTS

Simultaneous colonization by C. albicans was observed in the consorts of 12 couples (23.1%). Patterns of monoclonal and polyclonal oral colonization by C. albicans strains were identified and the coexistence of identical or highly related strains was observed in both members of eight couples. The genetic diversity observed in the total yeast population revealed four large, genetically distinct groups (A to D) and the coexistence of strains in couples or consorts conjugally unrelated. SAP and PL activity was observed in the majority of C. albicans isolates without any association to particular strain, strain clusters (highly related isolates), or clinical characteristics of the consorts (diabetic, non-diabetic, and gender).

CONCLUSION

Possible sources of transmission and oral propagation of groups (clusters) of strains of C. albicans can occur between diabetic and non-diabetic consorts. A conjugal genotypic identity exists in most C. albicans-positive couples, that is, both consorts share identical or highly related strains; however, this identity is not couple-specific as seen by the coexistence of clusters in couples and unrelated consorts.

Recent approaches to antifungal therapy for invasive mycoses

Invasive fungal infections with primary and opportunistic mycoses have become increasingly common in recent years and pose a major diagnostic and therapeutic challenge. They represent a major area of concern in today's medical fraternity. The occurrence of invasive fungal diseases, particularly in AIDS and other immunocompromised patients, is life-threatening and increases the economic burden. Apart from the previously known polyenes and imidazole-based azoles, newly discovered triazoles and echinocandins are more effective in terms of specificity, yet some immunosuppressed hosts are difficult to treat. The main reasons for this include antifungal resistance, toxicity, lack of rapid and microbe-specific diagnoses, poor penetration of drugs into sanctuary sites, and lack of oral or intravenous preparations. In addition to combination antifungal therapy, other novel antimycotic treatments such as calcineurin signaling pathway blockers and vaccines have recently emerged. This review briefly summarizes recent developments in the pharmacotherapeutic treatment of invasive fungal infections.

Structural elucidation of propargylated products of 3-substituted-1,2,4-triazole-5-thiols by NMR techniques

Propargylation of 3-substituted-1,2,4-triazole-5-thiols, which predominantly exist as their thione tautomers, was carried out with the view to synthesize different heterocycles and study their biological activity. Three different products namely, a mono S-propargyl and two S,N-dipropargyl regioisomers, arising from N1/N2 substitution, were isolated and characterized. Unambiguous structural elucidation of the regioisomers of S,N-dipropargyl derivatives was achieved by means of (13)C-(1)H HMBC technique. The proportion of the regioisomers was found to vary with the substituent on the 1,2,4-triazole thiols. No product corresponding to N4 substitution was isolated from any of the reactions carried out.

Glutamine analogues containing a keto function – novel inhibitors of fungal glucosamine-6-phosphate synthase

A series of novel inhibitors of glucosamine-6-phosphate synthase, analogues of AADP and BADP, have been synthesized and their inhibitory, lipophilic and antifungal properties have been tested. The improvement in lipophilicity has not much affected the antifungal activity of the new compounds. Dipeptides containing norvaline and selected inhibitors have shown substantial activity against S. cerevisiae and C. glabrata and only poor activity against C. albicans strain. These peptides do not seem to be toxic towards human cells.

Sordarin, an antifungal agent with a unique mode of action

The sordarin family of compounds, characterized by a unique tetracyclic diterpene core including a norbornene system, inhibits protein synthesis in fungi by stabilizing the ribosome/EF2 complex. This mode of action is in contrast to typical antifungals, which target the cell membrane. This unusual bioactivity makes sordarin a promising candidate for the development of new fungicidal agents, and provided the motivation for extensive research. Three total syntheses (by the Kato, Mander and Narasaka groups), modifications of the glycosyl unit, and changes to the diterpene core (Cuevas and Ciufolini models) will also be discussed in this review.

Inhibition of Candida albicans extracellular enzyme activity by selected natural substances and their application inCandidainfection

Extracellular enzymes secreted by Candida albicans are claimed to be virulence factors responsible for penetration of the yeast into host cells. Substances able to inhibit lipolytic and proteinase activities of the fungus might be of therapeutic use in some pathologic conditions caused by C. albicans. In the present work, we have tested the influence of the flavonoid compounds apigenin and kaempferol, the indole alkaloid ibogaine, and the protoberberine alkaloid berberine on the in vitro enzyme activity of C. albicans. The substances showed complex suppressive effects concerning the processes of adherence to epithelial cells, secreted aspartyl proteinase activity, and the rate of cell wall protein glycosylation. Apigenin and kaempferol were administered in systemic C. albicans infection, demonstrating an increased number of survivors by kaempferol. The application of apigenin, kaempferol, ibogaine, and berberine in cutaneous infection suppressed the symptoms and accelerated elimination of the yeast from the site of inoculation.

Synthesis and in vitro biological properties of novel cationic derivatives of amphotericin B

Novel cationic amphotericin B derivatives as highly potent antifungal agents are reported. These semi-synthetic derivatives of amphotericin B were elaborated through a series of modifications both on the nitrogen atom of the mycosamine and on the C-16 carboxylic acid moiety. The antifungal activity of the new conjugates was tested against Saccharomyces cerevisiae and also against nine different strains of Candida albicans and Candida glabrata, including an amphotericin resistant strain. High potency was observed in the case of polyamine derivatives bearing two 3-aminopropyl chains on the mycosamine. The evaluation of the biological properties also included the determination of the hemolytic activity of the compounds by measuring the EH50 values.

In Vitro antimycotic activity of xanthorrhizol isolated from Curcuma xanthorrhiza Roxb. against opportunistic filamentous fungi

Xanthorrhizol was isolated from the rhizome of Curcuma xanthorrhiza (Zingiberaceae) and its in vitro activity against opportunistic filamentous fungi was evaluated using the NCCLS (M38-A) standard method. Xanthorrhizol was found to be active against all the species tested, namely Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Fusarium oxysporum, Rhizopus oryzae and Trichophyton mentagrophytes: the MICs being 2.0, 2.0, 2.0, 4.0, 1.0 and 1.0 microg/mL, while the MFCs were 4.0, 4.0, 4.0, 8.0, 2.0 and 2.0 microg/mL, respectively. The susceptibility of six species of filamentous fungi to xanthorrhizol was comparable to that of the commercial antifungal, amphotericin B. Xanthorrhizol also has activity to inhibit the conidial germination of all tested species. The results strongly suggest that xanthorrhizol can be developed as a natural antifungal agent.

Strategies for the prevention of microbial biofilm formation on silicone rubber voice prostheses

Total laryngectomy, a surgical treatment for extensive cancer of larynx, which alters swallowing and respiration in patients, is followed up with a surgical voice restoration procedure comprising tracheoesophageal puncture techniques with insertion of a "voice prosthesis" to improve successful voice rehabilitation. However, microbial colonization is a major drawback of these devices. Antimicrobials are usually used to prevent the colonization of silicone rubber voice prostheses by microorganisms. However, long-term medication induces the development of resistant strains with all associated risks and the development of alternative prophylactic and therapeutic agents, including probiotics and biosurfactants, have been suggested. The inhibition of microbial growth on surfaces can also be achieved by several other techniques involving the modification of physicochemical properties of the biomaterial surface or the covalently binding of antimicrobial agents to the biomaterial surface. An overview of the different approaches investigated to date and future perspectives to reduce the frequent replacements of voice prostheses in laryngectomized patients through microbial biofilm retardation is presented and discussed.

Synthesis and antimicrobial activity of 1-(4-aryl-2-thiazolyl)-3-(2-thienyl)-5-aryl-2-pyrazoline derivatives

Several 1-(4-aryl-2-thiazolyl)-3-(2-thienyl)-5-aryl-2-pyrazoline derivatives were synthesized by reacting substituted 3-(2-thienyl)-5-aryl-1-thiocarbamoyl-2-pyrazolines with phenacyl bromides in ethanol. The structures of the synthesized compounds were confirmed by (1)H NMR, (13)C NMR, and EIMS spectral data. Their antimicrobial activities against Escherichia coli (NRRL B-3704), Staphylococcus aureus (NRLL B-767), Salmonella typhimurium (NRRL B-4420), Bacillus cereus (NRRL B-3711), Streptococcus faecalis (NRRL B-14617), Aeromonas hydrophila (Ankara Uni. Fac. of Veterinary), Candida albicans and Candida glabrata (isolates obtained from Osmangazi Uni. Fac. of Medicine) were investigated. A significant level of activity was observed.

Candidaemia in patients with haematological disorders and stem cell transplant

The incidence of non-albicans species of Candida has recently increased, especially in patients with malignant haematological disorders receiving fluconazole prophylaxis. A retrospective study of patients who developed candidaemia at Riyadh Armed Forces Hospital between January 1992 and December 2002 was carried out. Thirty one episodes of candidaemia occurred in 27 patients with a variety of haematological disorders. Twenty-four episodes were caused by non-albicans species of Candida and only 7 episodes were caused by C.albicans. The most frequent underlying haematological disorders were acute myeloid leukaemia (AML) followed by acute lymphoblastic leukaemia (ALL). The main predisposing factors for the development of candidaemia were: broad spectrum antibiotics, central venous catheters, neutropenia, cytotoxic chemotherapy, coexisting bacterial infections, steroid therapy, relapsing or untreated primary disease and fluconazole prophylaxis.

Eight episodes were complicated by chronic disseminated candidiasis. Amphotericin-B and amBisome were used in the treatment of Candida infections. The treatment was successful in 86% of the episodes of C. albicans and 50% of the episodes due to nonalbicans species of Candida. The highest mortality rate was encountered with C.tropicalis infections.

Candidaemia is an important cause of mortality and morbidity in patients with malignant haematological disorders and stem cell transplant. The predominance of non-albicans species of Candida especially C.krusei and C.tropicalis is alarming. The early administration of appropriate antifungal therapy and the removal of infected intravascular catheters improve the outcome considerably.

Nystatin in Langmuir monolayers at the air/water interface

The paper presents a thorough characteristics of Langmuir monolayers formed at the air/water interface by a polyene macrolide antibiotic-nystatin. The investigations are based on the analysis of pi/A isotherms recorded for monolayers formed by this antibiotic at different experimental conditions. A significant part of this work is devoted to the stability and relaxation phenomena. It has been found that nystatin forms at the air/water interface monolayers of the LE state. A plateau region, observed during the course of the isotherm compression, is suggested to be due to the orientational change of nystatin molecules from horizontal to vertical position. Quantitative analysis of the desorption of the monolayer material into bulk water indicates that the solubility of nystatin monolayers increases with surface pressure. At low surface pressures, the desorption of nystatin from a monolayer is controlled both by dissolution and by diffusion. However, at the plateau and in the post-plateau region, the desorption does not achieve a steady state and the monolayer is less stable than in the pre-plateau region. However, the presence of membrane lipids, even at a low mole fraction, considerably increases the stability of nystatin monolayers. This enables the application of the Langmuir monolayer technique to study nystatin in mixture with cellular membrane components, aiming at verifying its mode of action and the mechanism of toxicity.

Cryptococcal disease and HIV infection

In the era of highly active antiretroviral therapy for the treatment of HIV infection, the dramatic reductions in mortality and morbidity associated with immune reconstitution have included a marked decline in the incidence of opportunistic infections. Cryptococcus neoformans is a yeast that causes predominantly neurological disease in immunocompromised individuals, in particular those with HIV infection. It continues to be an important diagnosis in developing areas and amongst late presenters in parts of the world with access to highly active antiretroviral therapy. This article reviews the epidemiology, clinical features and management of cryptococcal disease in HIV-infected patients, particularly focusing on the history of, current guidelines for and future developments in antifungal therapy.

F2928-1 and -2, new antifungal antibiotics from Cladobotryum sp

Two new antifungal antibiotics, F2928-1 (1) and -2 (2), were isolated from the culture broth of Cladobotryum sp. These compounds were purified by solvent extraction, silica gel column chromatography and preparative HPLC, consecutively. The structures of these compounds were assigned as a decalin compound on the basis of various spectral analyses. These compounds showed antimicrobial activity against fungi including clinically important fungus, Aspergillus fumigatus.

Caspofungin as first line therapy of pulmonary invasive fungal infections in 32 immunocompromised patients with hematologic malignancies

Invasive Fungal Infections (IFI) remain a severe and major complication among patients with hematologic diseases, but the recent availability of new antifungal agents (echinocandins and new azoles) have improved the chance of cure. Caspofungin (Cancidas-Merck) is a large lipopeptide molecule able to inhibit the enzyme complex 1,3-d-glucan synthetase; this action specifically damages the fungal cell wall. Caspofungin (CAS) is active, in vitro and in vivo, against most Candida species and Aspergillus species. We report on our experience with this drug as first-line therapy for proven or probable pulmonary IFI in immunocompromised patients with hematologic malignancies. Thirty-two consecutive patients (20 males and 12 females, with a median age of 52 yr) have been treated with CAS (27 acute leukemias, 1 chronic leukemia, 3 lymphomas and 1 multiple myeloma). Sixteen patients (50%) had a relapsed or resistant hematologic disease, while 12 patients were in complete remission and 4 were at onset of disease; 8/32 (25%) developed IFI after a hematopoietic stem cell transplant (HSCT) procedure. Seven out of 32 patients (22%) had a proven pulmonary IFI (7/7 Aspergillosis) and 25 (78%) had a probable IFI with pulmonary localization as defined according to international consensus. Thirty-one patients (97%) had less than 1000 granulocytes/mL at onset of infection and at the start of CAS therapy. The CAS was given at the dose of 70 mg on day 1, followed by 50 mg/day. Median duration of CAS therapy was 20 d (range 8-64); all the 31 neutropenic patients received concomitant granulocyte colony-stimulating factor (G-CSF). The overall response rate was 56% (18/32) with 12/18 complete responses and 6/18 partial responses; two patients (6%) had a stable disease. Twelve out of 32 (38%) did not respond and seven died of mycotic infection. Univariate analysis showed that granulocytes recovery (>500/mL vs. <500/mL) and status of hematologic disease (remission/onset vs. refractory/relapsed) were significantly associated to favourable outcome. No clinical adverse events (AE) were reported and only a grades I and II transient increase of serum alkaline phosphatase and/or transaminases occurred in 4/32 (12%) patients. After CAS therapy six non-responders and six cases with a partial or stable response were rescued with voriconazole. Two out of six patients (33%) in the former group and 6/6 (100%) in the latter obtained a complete resolution of IFI. Our experience suggests an efficacy of CAS, in combination with G-CSF, as first-line treatment of proven or probable IFI with pulmonary localization. The drug was well tolerated and there were no significant hepatic AE even in patients receiving CAS with cyclosporine after a HSCT. A significant proportion of non-responders or partial responders to CAS can be rescued with a subsequent voriconazole-based therapy.

Ibogaine reduces organ colonization in murine systemic and gastrointestinal Candida albicans infections

In the present study the effect of the indole alkaloid ibogaine on the in vitro lipolytic activity and adherence to epithelial cells of Candida albicans was investigated. The substance was administered intraperitoneally at a dose of 5 mg kg(-1) day(-1) in mice with disseminated and gastrointestinal C. albicans infections. Ibogaine significantly decreased the rate of mortality and the number of C. albicans c.f.u. recovered from the kidney, liver and spleen. Ibogaine interfered with the early stages of both disseminated and gastrointestinal C. albicans infections but did not reduce the number of C. albicans c.f.u. in the organs at the late phase of infections. The development of a specific immune response was not influenced by ibogaine, since the delayed-type hypersensitivity reaction to C. albicans and the production of interferon (IFN)-gamma were similar in control and ibogaine-treated mice. The combined use of amphotericin B plus ibogaine in the treatment of mice with gastrointestinal infection reduced organ colonization more strongly than each substance alone.

Expression of genes encoding innate host defense molecules in normal human monocytes in response to Candida albicans

Little is known about the regulation and coordinated expression of genes involved in the innate host response to Candida albicans. We therefore examined the kinetic profile of gene expression of innate host defense molecules in normal human monocytes infected with C. albicans using microarray technology. Freshly isolated peripheral blood monocytes from five healthy donors were incubated with C. albicans for 0 to 18 h in parallel with time-matched uninfected control cells. RNA from monocytes was extracted and amplified for microarray analysis, using a 42,421-gene cDNA chip. Expression of genes encoding proinflammatory cytokines, including tumor necrosis factor alpha, interleukin 1 (IL-1), IL-6, and leukemia inhibitory factor, was markedly enhanced during the first 6 h and coincided with an increase in phagocytosis. Expression of these genes returned to near baseline by 18 h. Genes encoding chemokines, including IL-8; macrophage inflammatory proteins 1, 3, and 4; and monocyte chemoattractant protein 1, also were strongly up-regulated, with peak expression at 4 to 6 h, as were genes encoding chemokine receptors CCR1, CCR5, CCR7, and CXCR5. Expression of genes whose products may protect monocyte viability, such as BCL2-related protein, metallothioneins, CD71, and SOCS3, was up-regulated at 4 to 6 h and remained elevated throughout the 18-h time course. On the other hand, expression of genes encoding T-cell-regulatory molecules (e.g., IL-12, gamma interferon, and transforming growth factor beta) was not significantly affected during the 18-h incubation. Moreover, genes encoding IL-15, the IL-13 receptor (IL-13Ra1), and CD14 were suppressed during the 18-h exposure to C. albicans. Thus, C. albicans is a potent inducer of a dynamic cascade of expression of genes whose products are related to the recruitment, activation, and protection of neutrophils and monocytes.

Use of amphotericin B lipid complex in elderly patients

OBJECTIVES

The safety and effectiveness of amphotericin B lipid complex (ABLC) treatment in elderly patients was investigated using a large multicenter database.

METHODS

Data analysis was conducted on retrospectively collected patient data from 572 patients >65 years of age and 2930 patients < or =65 years of age treated for fungal infections at 160 North American hospitals.

RESULTS

Patients were typically treated with ABLC for Candidiasis, multiple fungal pathogen infections and Aspergillosis, or were treated empirically. The median cumulative dose of ABLC in patients >65 years of age and those 65 years of age was similar (3000 and 3258 mg, respectively, P=0.127). Despite higher median pretreatment serum creatinine (S-Cr) among patients >65 years of age (1.7 mg/dl vs. 1.4 mg/dl, respectively), both groups showed only a 0.1mg/dl median S-Cr change from baseline by the end of therapy (P=0.525). Clinical response was 56 and 51%, respectively, in patients >65 years of age and patients 65 years of age or younger (P=0.049).

CONCLUSIONS

This study suggests that ABLC can be safely and effectively used in the treatment of invasive fungal disease in elderly patients.

Colonization of Candida species in denture wearers with emphasis on HIV infection: a literature review

Candida colonization in denture wearers, especially immunocompromised patients, can be disruptive to dental treatment and may be a barrier to patient health. The surface irregularities of acrylic resin are a factor in the entrapment of microorganisms. Consequently, controlling the spread of fungal infection in HIV-infected patients who wear removable prostheses and who are more susceptible to fungal infections because of their immunosuppression is of critical importance. This article reviews the literature on the colonization of Candida species in HIV-infected denture wearers using keywords such as complete dentures, candidiasis, and HIV-infection . The source for this review was representative English-language, peer-reviewed articles between the period of 1885 to 2003 obtained using Medline, as well as a hand search.

Caspofungin as second-line therapy for fever of unknown origin or invasive fungal infection following allogeneic stem cell transplantation

Caspofungin (CAS) is the first of a new class of antifungal agents, the echinocandins, that interfere with fungal cell wall synthesis by inhibition of glucan synthesis. Here, we report the results of 31 patients treated with CAS following allogeneic SCT. CAS was administered as a second-line agent to patients with invasive fungal infection (IFI) (n=15) or fever of unknown origin (n=16) who were recalcitrant to or intolerant of prior antifungal therapy. Unsuccessful first-line regimes included amphotericin B (n=17), liposomal amphotericin B (n=5), fluconazole (n=3), itraconazole (n=1), and voriconazole (n=2). All patients received concomitant immunosuppressive therapy for graft-versus-host disease. In 23 patients, cyclosporin A (CSA) and CAS were administered concurrently without any major side effects detected. Observed increases in GPT were not clinically significant. Normalization of serum creatinine and significant reductions in C-reactive protein were observed in response to CAS. Favorable outcome to CAS were documented in eight of 15 patients with IFI and in 15 of 16 patients with fever of unknown origin. CAS is a promising alternative in patients with IFI and fever of unknown origin in the setting of allogeneic SCT.

In Vitro Antifungal Activity of ZJ-522, a New Triazole Restructured from Fluconazole and Butenafine, against Clinically Important Fungi in Comparison with Fluconazole and Butenafine

The antifungal activity of ZJ-522, a new triazole antifungal agent restructured from fluconazole and butenafine, was compared to that of fluconazole and butenafine against 43 strains of fungi representing 13 fungal species. MICs were determined by using the National Committee for Clinical Laboratory Standards (NCCLS)-recommended broth microdilution method for yeasts, which was modified for filamentous fungi. ZJ-522 was about 50-fold and 2 to 16-fold more potent than fluconazole against yeasts and filamentous fungi respectively, but it was less active than butenafine against filamentous fungi, although butenafine was inactive against most yeasts. Thus, the fashion of ZJ-522 antifungal activity more similar to that of fluconazole than that of butenafine indicates that ZJ-522 should be an inhibitor of lanosterol 14alpha-demethylase but not of squalene epoxidase, and should be a candidate for clinical development.

Antimycotic Drug Discovery in the Age of Genomics

Genomic-based methodologies are increasingly used at all stages of drug development. The most extensive applications have occurred in early drug discovery stages due to advances in technologies that allow for automated synthesis and characterization of organic compounds, and for high-throughput screening of these molecules against known drug targets. The adaptation of genomic-based methodologies in later stages of drug development presents a more difficult task. In this review we describe how genomics can be used to identify previously uncharacterized pharmacologic actions that provide a basis for the development of new classes of antimycotic agents or for adverse event aversion. Clinically, novel antimycotics are gravely needed. This review provides a perspective on new technologies that will bridge the gap between drug discovery and development that may enable more rapid access to new antimycotic agents.

Refractory pulmonary aspergillosis treated with caspofungin after heart-lung transplantation

Invasive pulmonary aspergillosis (IPA) is a serious complication of lung transplantation. Pre-mortem diagnosis is difficult and is made according to defined criteria. Most patients with a post mortem diagnosis of IPA only reach the possible or probable levels of diagnostic certainty during life. Here, we report a case of probable IPA that was refractory to conventional treatment, including amphotericin, but which responded to therapy with caspofungin. A 23-year-old man underwent heart-lung transplantation for cystic fibrosis. Ten years after transplantation he developed IPA. His condition continued to deteriorate despite treatment with itraconazole, liposomal amphotericin and flucytosine together with treatment of a concomitant infection with Pseudomonas aeruginosa. Following treatment with caspofungin there was progressive and sustained clinical and radiological improvement. No adverse reaction occurred during treatment. Caspofungin should be considered as an alternative treatment for IPA in lung transplant recipients who fail to respond to other therapy.

Rhodanine-3-acetic acid derivatives as inhibitors of fungal protein mannosyl transferase 1 (PMT1)

The first inhibitors of fungal protein: mannosyl transferase 1 (PMT1) are described. They are based upon rhodanine-3-acetic acid and several compounds have been identified, for example, 5-[[3-(1-phenylethoxy)-4-(2-phenylethoxy)phenyl]methylene]-4-oxo-2-thioxo-3-thiazolidineacetic acid (5a), which inhibit Candida albicans PMT1 with IC(50)s in the range 0.2-0.5 microM. Members of the series are effective in inducing changes in morphology of C. albicans in vitro that have previously been associated with loss of the transferase activity. These compounds could serve as useful tools for studying the effects of protein O-mannosylation and its relevance in the search for novel antifungal agents.

Fungal biofilms and drug resistance

Candida species, including the novel opportunistic pathogen Candida dubliniensis, are now emerging as major agents of nosocomial infections. Many such manifestations of infections associated with the formation of Candida biofilms include those occurring on devices such as indwelling intravascular catheters. Fungal biofilm-associated infections are frequently refractory to conventional therapy because of resistance to antimicrobial agents. This resistance could be in part due to the surface-induced upregulation of drug efflux pumps. Biofilm-associated Candida show uniform resistance to a wide spectrum of the currently available conventional antifungal agents, which implies that antimicrobial drugs that specifically target biofilm-associated infections are needed. The novel classes of antifungal agents, the lipid formulation of amphotericins, and the echinocandins have demonstrated unique antifungal activity against the resistant Candida biofilms, providing a breakthrough in the treatment of life-threatening invasive systemic mycoses. The use of drugs effective in combating biofilm-associated infections could lead to major developments in the treatment of fungal implant infections.

Antifungals and their use in veterinary ophthalmology

Many variables affect the outcome of keratomycosis and systemic fungal infections in animals. These include pathogenicity of the fungal organism(toxins, trophisms, and evasion of host response); previous treatment with topical or systemic corticosteroids, which can have a dramatic negative impact on host defense mechanisms: concurrent systemic illness or immunocompromise: severity/extent of infection; and degree of pain (ie,increased reflex tearing dilutes topical medication) [14]. Experimental work suggests that antibiotics may occasionally exacerbate fungal infections [142],and some researchers advocate that concurrent antibiotic therapy is contraindicated in horses with yeast infections and septate fungal infections unless bacterial infection is also suspected [14]. Nevertheless, given that normal conjunctival flora often include bacteria and fungi and because care of keratomycoses often includes mixed bacterial and fungal infections, the possible dynamics (natural influences and local competition) between ocular surface microorganisms merit further investigation. There are many unanswered questions regarding the accuracy of in vitro susceptibilities and corneal concentration capabilities for antifungal topical medications [14]. Inherent host resistance or other immune interactions between the patient and fungus are perhaps the most important determinants of the outcome but are currently difficult to measure or assess except by subjective clinical observation [14].

Caspofungin—a new therapeutic option for oropharyngeal candidiasis

Patients with AIDS are often severely immunocompromised. These patients commonly develop opportunistic infections such as oropharyngeal candidiasis whose treatment may prove to be difficult. Caspofungin belongs to a new class of antifungal agents that have a different mode of action to azoles and polyenes. This new agent is the first inhibitor of fungal glucan synthesis to receive approval for the treatment of mucosal and invasive candidiasis and invasive aspergillosis. Caspofungin is well-tolerated and represents a substantial improvement over existing therapeutic options for patients prone to azole-resistant candida infection or who cannot tolerate amphotericin B.

Co-administration of caspofungin and cyclosporine to a kidney transplant patient with pulmonary Aspergillus infection

A kidney transplant patient on cyclosporine treatment developed focal pneumonia due to Aspergillus fumigatus. The patient was not able to tolerate amphotericin B deoxycholate and was switched to caspofungin. The patient responded favourably without any evidence of toxicity from concomitant use of caspofungin and cylosporine.

Screening of nonpolyenic antifungal metabolites produced by clinical isolates of actinomycetes

The purpose of this work was to screen clinical isolates of actinomycetes producing nonpolyenic antifungals. This choice was made to limit the problem of rediscovery of well-known antifungal families, especially polyenic antifungals. One hundred and ten strains were tested, using two diffusion methods and two test media, against three yeast species and three filamentous fungi. Among 54 strains (49%) showing antifungal activity, five strains belonging to the genus Streptomyces were active against all test organisms and appeared promising. These results indicate that clinical and environmental isolates of actinomycetes could be an interesting source of antifungal bioactive substances. The production of nonpolyenic antifungal substances by these five active isolates was investigated using several criteria: antibacterial activity, ergosterol inhibition, and UV-visible spectra of active extracts. One active strain responded to all three selection criteria and produced potentially nonpolyenic antifungal metabolites. This strain was retained for further investigation, in particular, purification, structure elucidation, and mechanism of action of the active product.Key words: actinomycetes, Streptomyces, clinical isolates, antifungal, non-polyene.

Antifungal agents from the roots of Cudrania cochinchinensis against Candida, Cryptococcus, and Aspergillus species

Bioassay-guided fractionation resulted in the isolation of four antifungal agents from the roots of Cudrania cochinchinensis. Two of these were new compounds, cudraxanthone S [1, 1,3,5,6-tetrahydroxy-2-(1,1-dimethyl-2-propenyl)xanthone] and cudraflavanone B (2, 2',4',5,7-tetrahydroxy-6-prenylflavanone). The remaining two compounds were known compounds, toxyloxanthone C (3) and wighteone (4). Among these compounds, 1, 3, and 4 exhibited antifungal activities against Cryptococcus neoformans, Aspergillusfumigatus, and A. nidulans (MICs = 2-8 microg/mL). Compounds 1 and 3 also showed antifungal activity against Candida glabrata (MICs = 4-8 microg/mL).

Review of the safety, tolerability, and drug interactions of the new antifungal agents caspofungin and voriconazole

Managing invasive fungal infections often presents a challenge for clinicians in the treatment of immunocompromised patients. Two very different systemic antifungal agents, voriconazole and caspofungin, have recently been introduced into the market place. Voriconazole is a new triazole antifungal, while caspofungin is the first echinocandin antifungal. Voriconazole acts by inhibiting the synthesis of ergosterol in the fungal cell membrane. Caspofungin inhibits beta-1,3-D-glucan synthesis in the cell wall, a target present in fungal cells, but absent from mammalian cells. Both agents are broad-spectrum, with efficacy against invasive Aspergillus and Candida infections. The safety and tolerability profile of caspofungin presented with a low incidence of adverse events in clinical trials. Pending further data, coadministration of cyclosporine has been recommended only if the benefit outweighs the risk for patients. Voriconazole has three important side-effects that the clinician must consider: liver abnormalities, skin abnormalities and visual disturbances. Liver abnormalities in particular should be monitored very carefully. The drug interaction profile of voriconazole also warrants a careful evaluation of the concomitant medication, mainly due to cytochrome P450 metabolism. This article reviews the available data concerning the safety and tolerability profiles of each drug, as well as drug interactions and contraindications.

Single-nucleotide polymorphisms (SNPs) in human beta-defensin 1: high-throughput SNP assays and association with Candida carriage in type I diabetics and nondiabetic controls

beta-Defensins are cationic antimicrobial peptides expressed in epithelia. They exhibit antibacterial, antifungal, and antiviral properties. Defensins are a component of the innate immune response, and it has been proposed that they have a protective role in the oral cavity. Previous studies have shown that human beta-defensin 1 (hBD-1) is constitutively expressed in oral epithelial cells but that expression varies between individuals. We tested the hypothesis that genetic variations in defensin peptide expression may be associated with opportunistic infections. This may be critical in the immunocompromised patient population, in which innate immune responses may have a relatively more important role. Oral Candida carriage status and the presence of six single-nucleotide polymorphisms (SNPs) in the DEFB1 gene encoding hBD-1 were evaluated in type I diabetic patients (n = 43) and nondiabetic controls (n = 50). Genomic DNA was obtained from buccal swabs. Portions of the DEFB1 gene were amplified, and each SNP was analyzed by a TaqMan assay, standardized with control DNA of known genotype. Candida carriage status was determined from unstimulated saliva on CHROMagar plating medium. A low level of Candida carriage was defined as < or = 350 CFU/ml. A high level of Candida carriage was seen in 44% of the diabetic subjects but only in 28% of the nondiabetic controls (P < 0.05). C. albicans predominated; however, diabetic subjects, especially those with high levels of carriage, showed an increased proportion of Candida glabrata and C. tropicalis. There was a strong association between an SNP in the 5' untranslated region (C-->G at position -44) and Candida carriage in both groups. Among individuals in the diabetic population who had the SNP allele 2 (G), 58% had low CFU, while 6% had high CFU. The C-->G SNP at position -44 is associated with low levels of Candida carriage. The resultant odd ratios are statistically significant for a protective effect (odd ratios, 25 for diabetic subjects and 8.5 for nondiabetic subjects). These results indicate that genetic variations in the DEFB1 gene encoding hBD-1 may have a major role in mediating and/or contributing to susceptibility to oral infection.

In vitro activity of a new antifungal azolyl-substituted indole against Aspergillus fumigatus

A new 2-(alpha-azolylbenzyl)indole derivative exhibited high in vitro activity against 10 strains of Aspergillus fumigatus. This active compound, MT18n, had MIC of 2 microg/mL and is slightly less active than itraconazole and amphotericin B. The mechanism of action of this compound was evaluated through scanning electron microscopy, ergosterol biosynthesis inhibition and phospholipase A2-like activity inhibition studies. Scanning electron microscopy allowed observation of the membrane perturbations caused by MT18n and inference of a critical role of MT18n in membrane synthesis inhibition. Like other azole derivatives MT18n inhibits ergosterol biosynthesis, with a minimal inhibitory concentration of 6 microM. On the other hand, MT18n (10 microM) decreased the secreted phospholipase A2-like activity of Aspergillus fumigatus, an enzyme involved in the invasion process of the host. These results show the high in vitro activity of MT18n against Aspergillus fumigatus and suggest that this compound disturbs the membrane structure via ergosterol biosynthesis inhibition and exhibits phospholipase activity inhibition.

Efficacy of caspofungin in the treatment of esophageal candidiasis resistant to fluconazole

Caspofungin is a new echinocandin drug with comparable in vitro activity against azole-susceptible and -resistant isolates of that could provide a less toxic alternative to amphotericin B for the management of esophageal candidiasis with clinical or laboratory evidence of decreased susceptibility to fluconazole. The authors retrospectively analyzed its efficacy in adults with endoscopically documented esophagitis from four Phase II and III studies using two definitions of resistance to fluconazole: 1) clinically refractory infection based on failure of esophageal symptoms to improve despite at least 1 week of >or=200 mg/d of fluconazole; or 2) microbiologically resistant infection with either "susceptible dose-dependent" or "resistant" isolates based on MICs of 16 to 32 and >or=64 microg fluconazole/mL, respectively. A favorable response required resolution of all symptoms and substantial improvement in endoscopic findings. Seven of 11 patients (64%) who had been clinically refractory to fluconazole had favorable responses to caspofungin. Eleven of 14 patients (79%) whose isolates had decreased susceptibility to fluconazole had favorable responses to caspofungin, including 5 (83%) of 6 patients infected by isolates with MICs of >or=64 microg fluconazole/mL. Caspofungin appeared to be efficacious therapy for some patients with esophageal candidiasis who were clinically refractory to fluconazole or infected by with reduced susceptibility to fluconazole in vitro.

A randomized double-blind study of caspofungin versus fluconazole for the treatment of esophageal candidiasis

BACKGROUND

Candida esophagitis remains an important cause of morbidity in patients with advanced human immunodeficiency virus (HIV) infection. Fluconazole is widely regarded as the treatment of choice for this condition.

METHODS

The efficacy and safety of caspofungin were compared with fluconazole in adult patients with Candida esophagitis in a double-blind randomized trial. Eligible patients had symptoms compatible with esophagitis, endoscopic demonstration of mucosal plaques, and microscopic demonstration of Candida from the esophageal lesions. Patients were randomly assigned to receive caspofungin (50 mg) or fluconazole (200 mg) intravenously once daily for 7 to 21 days. The primary endpoint was the combined response of symptom resolution and significant endoscopic improvement 5 to 7 days after discontinuation of treatment. Data were analyzed with a modified intention-to-treat analysis, which excluded 2 ineligible patients.

RESULTS

Most patients (154/177; 87%) had HIV infection, with a median CD4 count of 30 cells/mm(3). Candida albicans was the predominant isolate. Favorable response rates were achieved in 66 (81%) of the 81 patients in the caspofungin arm and in 80 (85%) of the 94 patients in the fluconazole arm (difference = -4%; 95% confidence interval: -15% to +8%). Symptoms had resolved in >50% of patients in both groups by the fifth day of treatment. No patient in the caspofungin group developed a serious drug-related adverse event; therapy was only discontinued in 1 patient (receiving fluconazole) due to a drug-related adverse experience. Four weeks after stopping study drug, symptoms had recurred in 18 (28%) of 64 patients given caspofungin and in 12 (17%) of 72 patients given fluconazole (P = 0.19).

CONCLUSIONS

In this study, caspofungin appeared to be as efficacious and generally as well tolerated as fluconazole in patients with advanced HIV infection and documented Candida esophagitis.

Response and relapse rates of candidal esophagitis in HIV-infected patients treated with caspofungin

Caspofungin is a new antifungal drug of the echinocandin class. We analyzed the clinical efficacy of caspofungin (50 mg/day) in the treatment of HIV-infected adults with endoscopically documented Candida esophagitis and enrolled in four clinical trials of caspofungin. Symptoms were evaluated daily; a favorable outcome required complete resolution of all esophageal symptoms assessed at the time of discontinuation of therapy. Relapse was defined as recurrent symptoms during the subsequent 2 weeks. A multivariate logistic regression model was developed to identify potential factors (including severity of symptoms at presentation, CD4(+) cell count on entry, extent of disease [assessed endoscopically at baseline], causative Candida species, duration of therapy [overall and after resolution of symptoms], time on treatment before symptom resolution, and antifungal prophylaxis) that might predict symptomatic relapse in the 2 weeks following completion of therapy. The median CD4(+) lymphocyte count for the entire population was 31/mm(3). Candida albicans was isolated from 109 of 110 patient samples cultured for the pathogen and constituted the sole isolate in 77%. Extensive esophageal involvement was present in 55% of patients at the time of pretreatment endoscopy. The duration of therapy ranged from 7 to 20 days (median, 12 days). Symptoms resolved in 117 of 123 patients (95%; 95% confidence interval, 90-98%) with a median time of ~4 days. Response rates were 43 of 46 (93%) and 70 of 73 (96%) for patients with greater or fewer than 50 CD4(+) cells/mm(3), and 80 of 85 (94%) and 23 of 24 (96%) in infections caused by C. albicans alone or in association with non-albicans isolates, respectively. Symptoms recurred within 2 weeks of stopping caspofungin in 19 of 115 evaluable patients (17%), including 3 of 16 (19%) receiving antifungal prophylaxis. Relapse rates were similar for patients with greater or fewer than 50 CD4(+) cells/mm(3). In this relatively small number of patients, only symptom severity and extent of disease judged endoscopically at baseline were significantly (p < 0.10) associated with early relapse in the multivariate model.

[New antifungal antibiotics, bacillopeptins and fusaricidins]

We isolated four strains of bacteria producing antifungal antibiotics from the rhizosphere of garlic with basal rot caused by the plant pathogenic fungal strain Fusarium oxysporum. Among them, Bacillus subtilis FR-2 was found to produce new antifungal antibiotics, named bacillopeptins A, B, and C. Their structures have been determined by 1D and 2D NMR and MS experiments, and amino acid analysis coupled with chiral HPLC, to be cyclic lipopeptides each containing a long-chain beta-amino acid. Another bacterial strain, Bacillus polymyxa KT-8, was shown to produce new antifungal antibiotics named fusaricidins A, B, C, and D which are more potent than bacillopeptins in their antimicrobial activity. The structures of the fusaricidins have been elucidated similarly as bacillopeptins to be cyclic hexadepsipeptides all containing 15-guanidino-3-hydroxypentadecanoic acid as a side chain. Fusaricidins strongly inhibit the growth of various kinds of fungi and moreover surprisingly show strong inhibitory activity against Gram-positive bacteria such as Staphylococcus aureus or Micrococcus luteus.