Resistance to amphotericin B: emerging clinical and microbiological patterns

Snakes as sentinel of zoonotic yeasts and bio-indicators of environmental quality

Reptiles in the wild or as pets may act as spreaders of bacteria, viruses, fungi and parasites. However, studies on the mycobiota of these animals are scanty. This study investigates the occurrence of yeasts from the cloacal swabs of snakes of different origins and the antifungal profile of the isolated strains. A total of 180 cloacal samples of snakes were collected from Morocco (Group I: n = 68) and Italy (Group II: n = 112). Yeast species were biochemically and molecularly identified. A total of 72 yeast strains belonging to 13 genera, 8 from snakes in Group I and five from snakes in Group II were identified. The most frequently isolated species were Trichosporon asahii (22.2%) and Candida tropicalis (15.3%) from snakes in Group I and Debaryomyces spp. (16.7%) and Metahyphopichia silvanorum (11.1%) from snakes in Group II. Multiple azole and amphotericin B (AmB) resistance phenomena were detected among isolated yeasts. Azole multi drug resistance phenomena were detected among yeasts from Group I and Rhodotorula mucilaginosa from Group II, whereas AmB resistance phenomena among those from Group II. Data suggest that snakes may harbor pathogenetic yeasts, being potential reservoirs and spreaders of these organisms in the environment. Since the yeast species community from different groups of animals as well as their antifungal profile reflects the epidemiology of human yeast infections in the same geographical areas, the results indicate that snakes may be considered as sentinels for human/animal pathogenic microorganisms and bio-indicators of environmental quality.

The sterol C-24 methyltransferase encoding gene, erg6, is essential for viability of Aspergillus species

Triazoles, the most widely used class of antifungal drugs, inhibit the biosynthesis of ergosterol, a crucial component of the fungal plasma membrane. Inhibition of a separate ergosterol biosynthetic step, catalyzed by the sterol C-24 methyltransferase Erg6, reduces the virulence of pathogenic yeasts, but its effects on filamentous fungal pathogens like Aspergillus fumigatus remain unexplored. Here, we show that the lipid droplet-associated enzyme Erg6 is essential for the viability of A. fumigatus and other Aspergillus species, including A. lentulus, A. terreus, and A. nidulans. Downregulation of erg6 causes loss of sterol-rich membrane domains required for apical extension of hyphae, as well as altered sterol profiles consistent with the Erg6 enzyme functioning upstream of the triazole drug target, Cyp51A/Cyp51B. Unexpectedly, erg6-repressed strains display wild-type susceptibility against the ergosterol-active triazole and polyene antifungals. Finally, we show that erg6 repression results in significant reduction in mortality in a murine model of invasive aspergillosis. Taken together with recent studies, our work supports Erg6 as a potentially pan-fungal drug target.

The sterol C-24 methyltransferase encoding gene, erg6, is essential for viability of Aspergillus species

Ergosterol is a critical component of fungal plasma membranes. Although many currently available antifungal compounds target the ergosterol biosynthesis pathway for antifungal effect, current knowledge regarding ergosterol synthesis remains incomplete for filamentous fungal pathogens like Aspergillus fumigatus. Here, we show for the first time that the lipid droplet-associated sterol C-24 methyltransferase, Erg6, is essential for A. fumigatus viability. We further show that this essentiality extends to additional Aspergillus species, including A. lentulus, A. terreus, and A. nidulans. Neither the overexpression of a putative erg6 paralog, smt1, nor the exogenous addition of ergosterol could rescue erg6 deficiency. Importantly, Erg6 downregulation results in a dramatic decrease in ergosterol and accumulation in lanosterol and is further characterized by diminished sterol-rich plasma membrane domains (SRDs) at hyphal tips. Unexpectedly, erg6 repressed strains demonstrate wild-type susceptibility against the ergosterol-active triazole and polyene antifungals. Finally, repressing erg6 expression reduced fungal burden accumulation in a murine model of invasive aspergillosis. Taken together, our studies suggest that Erg6, which shows little homology to mammalian proteins, is potentially an attractive antifungal drug target for therapy of Aspergillus infections.

Synergistic Antifungal Interactions between Antibiotic Amphotericin B and Selected 1,3,4-thiadiazole Derivatives, Determined by Microbiological, Cytochemical, and Molecular Spectroscopic Studies

In recent years, drug-resistant and multidrug-resistant fungal strains have been more frequently isolated in clinical practice. This phenomenon is responsible for difficulties in the treatment of infections. Therefore, the development of new antifungal drugs is an extremely important challenge. Combinations of selected 1,3,4-thiadiazole derivatives with amphotericin B showing strong synergic antifungal interactions are promising candidates for such formulas. In the study, microbiological, cytochemical, and molecular spectroscopy methods were used to investigate the antifungal synergy mechanisms associated with the aforementioned combinations. The present results indicate that two derivatives, i.e., C1 and NTBD, demonstrate strong synergistic interactions with AmB against some Candida species. The ATR-FTIR analysis showed that yeasts treated with the C1 + AmB and NTBD + AmB compositions, compared with those treated with single compounds, exhibited more pronounced abnormalities in the biomolecular content, suggesting that the main mechanism of the synergistic antifungal activity of the compounds is related to a disturbance in cell wall integrity. The analysis of the electron absorption and fluorescence spectra revealed that the biophysical mechanism underlying the observed synergy is associated with disaggregation of AmB molecules induced by the 1,3,4-thiadiazole derivatives. Such observations suggest the possibility of the successful application of thiadiazole derivatives combined with AmB in the therapy of fungal infections.

Emerging Prospects for Combating Fungal Infections by Targeting Phosphatidylinositol Transfer Proteins

The emergence of fungal “superbugs” resistant to the limited cohort of anti-fungal agents available to clinicians is eroding our ability to effectively treat infections by these virulent pathogens. As the threat of fungal infection is escalating worldwide, this dwindling response capacity is fueling concerns of impending global health emergencies. These developments underscore the urgent need for new classes of anti-fungal drugs and, therefore, the identification of new targets. Phosphoinositide signaling does not immediately appear to offer attractive targets due to its evolutionary conservation across the Eukaryota. However, recent evidence argues otherwise. Herein, we discuss the evidence identifying Sec14-like phosphatidylinositol transfer proteins (PITPs) as unexplored portals through which phosphoinositide signaling in virulent fungi can be chemically disrupted with exquisite selectivity. Recent identification of lead compounds that target fungal Sec14 proteins, derived from several distinct chemical scaffolds, reveals exciting inroads into the rational design of next generation Sec14 inhibitors. Development of appropriately refined next generation Sec14-directed inhibitors promises to expand the chemical weaponry available for deployment in the shifting field of engagement between fungal pathogens and their human hosts.

Polyhydroxyalkanoate/Antifungal Polyene Formulations with Monomeric Hydroxyalkanoic Acids for Improved Antifungal Efficiency

Novel biodegradable and biocompatible formulations of "old" but "gold" drugs such as nystatin (Nys) and amphotericin B (AmB) were made using a biopolymer as a matrix. Medium chain length polyhydroxyalkanoates (mcl-PHA) were used to formulate both polyenes (Nys and AmB) in the form of films (~50 µm). Thermal properties and stability of the materials were not significantly altered by the incorporation of polyenes in mcl-PHA, but polyene containing materials were more hydrophobic. These formulations were tested in vitro against a panel of pathogenic fungi and for antibiofilm properties. The films containing 0.1 to 2 weight % polyenes showed good activity and sustained polyene release for up to 4 days. A PHA monomer, namely 3-hydroxydecanoic acid (C10-OH), was added to the films to achieve an enhanced synergistic effect with polyenes against fungal growth. Mcl-PHA based polyene formulations showed excellent growth inhibitory activity against both Candida yeasts (C. albicans ATCC 1023, C. albicans SC5314 (ATCC MYA-2876), C. parapsilosis ATCC 22019) and filamentous fungi (Aspergillus fumigatus ATCC 13073; Trichophyton mentagrophytes ATCC 9533, Microsporum gypseum ATCC 24102). All antifungal PHA film preparations prevented the formation of a C. albicans biofilm, while they were not efficient in eradication of mature biofilms, rendering them suitable for the transdermal application or as coatings of implants.

Antifungal resistance in Superficial mycoses

BACKGROUND AND OBJECTIVE

With the widespread use of antifungals to treat superficial mycoses, reports of antifungal resistance are increasing. Antifungal resistance is becoming a public health challenge and needs to be addressed in parallel with antibacterial and antiviral resistance.

METHODS

We review the growing resistance of fungal pathogens such as Trichophyton species and the emergence of novel pathogens, including multidrug-resistant strains in superficial mycoses. We also discuss the importance of laboratory diagnosis and antifungal susceptibility testing (AFST) in the management of recalcitrant infections.

RESULTS AND CONCLUSION

Antifungal resistance can occur naturally or develop over time when fungi are exposed to antifungals. The frequency of terbinafine-resistant Trichophyton isolates is increasing. Opportunistic pathogens such as Aspergillus and Candida species have developed resistance to classic azoles such as itraconazole and fluconazole, and the newer azoles such as posaconazole and voriconazole. Although uncommon, topical antifungals such as efinaconazole and tavaborole have shown to induce resistance in Trichophyton rubrum. The emergence of multidrug-resistant Trichophyton mentagrophytes/interdigitale, Candida auris, and Aspergillus species causing severe infections is highly concerning. Routine AFST should be considered to determine the most effective treatment, especially if there is failure to therapy. Combination treatment of oral and topical antifungals may be a consideration for managing recalcitrant infections.

A Review on Molecular Mechanisms of Antifungal Resistance in Candida glabrata: Update and Recent Advances

Candida glabrata is the second frequent etiologic agent of mucosal and invasive candidiasis. Based on the recent developments in molecular methods, C. glabrata has been introduced as a complex composed of C. glabrata, Candida nivariensis, and Candida bracarensis. The four main classes of antifungal drugs effective against C. glabrata are pyrimidine analogs (flucytosine), azoles, echinocandins, and polyenes. Although the use of antifungal drugs is related to the predictable development of drug resistance, it is not clear why C. glabrata is able to rapidly resist against multiple antifungals in clinics. The enhanced incidence and antifungal resistance of C. glabrata and the high mortality and morbidity need more investigation regarding the resistance mechanisms and virulence associated with C. glabrata; additional progress concerning the drug resistance of C. glabrata has to be further prevented. The present review highlights the mechanism of resistance to antifungal drugs in C. glabrata.

Synergistic Effect of Pyrvinium Pamoate and Azoles Against Aspergillus fumigatus in vitro and in vivo

The effects of pyrvinium pamoate alone and in combination with azoles [itraconazole (ITC), posaconazole (POS), and voriconazole (VRC)] were evaluated against Aspergillus fumigatus both in vitro and in vivo. A total of 18 clinical strains of A. fumigatus were studied, including azole-resistant isolates harboring the combination of punctual mutation and a tandem repeat sequence in the Cyp51A gene (AFR1 with TR34/L98H and AFR2 with TR46/Y121F/T289A). The in vitro results revealed that pyrvinium individually exhibited minimal inhibitory concentration (MIC) of 2 μg/ml against AFR1 but was ineffective against other tested strains (MIC > 32 μg/ml). Nevertheless, the synergistic effects of pyrvinium with ITC, VRC, or POS were observed in 15 [83.3%, fractional inhibitory concentration index (FICI) 0.125-0.375], 11 (61.1%, FICI 0.258-0.281), and 16 (88.9%, FICI 0.039-0.281) strains, respectively, demonstrating the potential of pyrvinium in reversion of ITC and POS resistance of both AFR1 (FICI 0.275, 0.281) and AFR2 (FICI 0.125, 0.039). The effective MIC ranges in synergistic combinations were 0.25-8 μg/ml for pyrvinium, 0.125-4 μg/ml for ITC, and 0.125 μg/ml for both VRC and POS, demonstrating 4- to 32-fold reduction in MICs of azoles and up to 64-fold reduction in MICs of pyrvinium, respectively. There was no antagonism. The effect of pyrvinium-azole combinations in vivo was evaluated by survival assay and fungal burden determination in the Galleria mellonella model infected with AF293, AFR1, and AFR2. Pyrvinium alone significantly prolonged the survival of larvae infected with AF293 (P < 0.01) and AFR1 (P < 0.0001) and significantly decreased the tissue fungal burden of larvae infected with AFR1 (P < 0.0001). Pyrvinium combined with azoles significantly improved larvae survival (P < 0.0001) and decreased larvae tissue fungal burden in all three isolates (P < 0.0001). Notably, despite AFR2 infection was resistant to VRC or pyrvinium alone, pyrvinium combined with VRC significantly prolonged survival of both AFR1 and AFR2 infected larvae (P < 0.0001). In summary, the preliminary results indicated that the combination with pyrvinium and azoles had the potential to overcome azole resistance issues of A. fumigatus and could be a promising option for anti-Aspergillus treatment.

A comprehensive overview of the medicinal chemistry of antifungal drugs: perspectives and promise

The emergence of new fungal pathogens makes the development of new antifungal drugs a medical imperative that in recent years motivates the talents of numerous investigators across the world. Understanding not only the structural families of these drugs but also their biological targets provides a rational means for evaluating the merits and selectivity of new agents for fungal pathogens and normal cells. An equally important aspect of modern antifungal drug development takes a balanced look at the problems of drug potency and drug resistance. The future development of new antifungal agents will rest with those who employ synthetic and semisynthetic methodology as well as natural product isolation to tackle these problems and with those who possess a clear understanding of fungal cell architecture and drug resistance mechanisms. This review endeavors to provide an introduction to a growing and increasingly important literature, including coverage of the new developments in medicinal chemistry since 2015, and also endeavors to spark the curiosity of investigators who might enter this fascinatingly complex fungal landscape.

Givinostat exhibits in vitro synergy with posaconazole against Aspergillus spp

In vitro interactions of givinostat, a hydroxamate-derived histone deacetylase inhibitor, and antifungals including itraconazole, voriconazole, posaconazole, amphotericin B and caspofungin against Aspergillus spp. were assessed via broth microdilution checkerboard technique system. A total of 30 isolates of Aspergillus spp., including 20 strains of A. fumigatus and 10 strains of A. flavus were studied. The results revealed favorable synergistic effects between givinostat and posaconazole (83.3%) against Aspergillus isolates. Limited synergism was observed when givinostat was combined with itraconazole or voriconazole. No interaction was observed between givinostat and amphotericin B or caspofungin. No antagonism was observed in all combinations.

Clinical pharmacology of antifungal agents to overcome drug resistance in pediatric patients

INTRODUCTION

Antifungal resistance is an emerging problem that increases morbidity and mortality in immunosuppressed pediatric patients, who suffer from invasive fungal diseases. Optimal pharmacological management is critical for the successful treatment of invasive fungal infections by resistant strains.

AREAS COVERED

This paper reviews the mechanisms of resistance of different classes of antifungal agents and the current understanding of pediatric antifungal pharmacology for overcoming antifungal resistance in children based on laboratory and clinical studies in the English literature. The therapeutic choices against fungal pathogens with intrinsic or acquired resistance are further reviewed.

EXPERT OPINION

There is a paucity of data in the pediatric population regarding the epidemiology of the resistant organisms to different antifungal agents. It is also unknown if there are more prevalent molecular mechanisms that promote antifungal resistance. Selection and dosages of the most effective antifungal agent for overcoming the antifungal resistance is crucial. However, there are limited studies guiding the optimal dosage and duration of treatment for management of emergent antifungal resistance. Further studies are warranted to elucidate the optimal pharmacology of the current antifungal agents against resistant organisms and to advance the development of new antifungal agents.

Prior in vitro exposure to voriconazole confers resistance to amphotericin B in Aspergillus fumigatus biofilms

Triazoles are the mainstay of treatment for aspergillosis, although resistance to these antifungal agents may be associated with treatment failure. Refractory infections often necessitate a switch to other antifungal agents, including amphotericin B (AmB), although these infections may not resolve. The aim of this study was to investigate the effect of prior azole exposure on AmB sensitivity in Aspergillus fumigatus biofilms. It was hypothesised that sequential antifungal therapy has the potential to impact adaptive resistance mechanisms. Antifungal sensitivity was determined for each isolate against AmB±voriconazole (VRZ) exposure by a broth microdilution method and an XTT metabolic assay. To analyse the role of extracellular DNA (eDNA) and Hsp90 activation, sensitivity to AmB±DNA-digesting enzyme (DNase) or Hsp90 inhibitor [geldanamycin (GDA)] was also tested. Finally, scanning electron microscopy was performed to assess phenotypic changes. The in vitro data revealed that A. fumigatus sensitivity to AmB was decreased when it was tested in combination with VRZ. In addition, a two- to four-fold decreased sensitivity to AmB was recorded against VRZ-exposed germlings compared with controls. It was also shown that depletion of eDNA by DNase treatment enhanced AmB activity against VRZ-exposed cells by eight-fold, which visually could be explained by destabilisation of the biofilm when examined microscopically. Pharmacological inhibition of Hsp90 by GDA significantly improved biofilm susceptibility to AmB by four- to eight-fold. In conclusion, A. fumigatus pre-exposure to VRZ concomitantly induces eDNA release and activates the stress response, which collectively confers AmB resistance in vitro.

Comparative Evaluation of Disc Diffusion and E-test with Broth Micro-dilution in Susceptibility testing of Amphotericin B, Voriconazole and Caspofungin against Clinical Aspergillus isolates

BACKGROUND

Clinical importance of Aspergillus has increased over the past few decades because of rise in immunosuppressive drugs and immune-modulating diseases. Antifungal susceptibility of Aspergillus is rarely performed by clinical laboratories because of lack of easier method. This study has investigated and compared susceptibility pattern of Aspergillus isolates by disc diffusion, E-test and broth micro-dilution for amphotericin B, voriconazole and caspofungin.

MATERIALS AND METHODS

Disk diffusion (DD) method of antifungal susceptibility (AFS) was evaluated for three different classes of antifungals: amphotericin B (AMB), voriconazole (VCZ) and caspofungin (CAS). Forty four clinical isolates of Aspergillus were selected; these included 34 A.fumigatus, 8 A.flavus and 2 A. terreus. AFS by DD and E-test was done on non-supplemented Mueller Hinton Agar (MHA) and was compared to Clinical Laboratory Standard Institute(CLSI) broth micro-dilution (BMD) method of AFS.

RESULTS

Disk diffusion method for amphotericin B showed 87.5% agreement while E-test showed 93.8% agreement with broth micro-dilution. The agreement with broth micro-dilution was similar for both disk diffusion and E-test in case of voriconazole (93.8%) and caspofungin (100%). 31.8% and 9.1% Aspergillus isolates were found to have amphotericin B and voriconazole MIC values above epidemiological cut off value (ECV) respectively. All isolates were within ECV for caspofungin.

CONCLUSION

CLSI method of DD promises to be easier, reproducible and cost effective method of susceptibility testing, but this method must be interpreted with caution in case of amphotericin B susceptibility testing. E-test correlates better than DD with BMD.

Elucidating drug resistance in human fungal pathogens

Fungal pathogens cause life-threatening infections in immunocompetent and immunocompromised individuals. Millions of people die each year due to fungal infections, comparable to the mortality attributable to tuberculosis or malaria. The three most prevalent fungal pathogens are Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus. Fungi are eukaryotes like their human host, making it challenging to identify fungal-specific therapeutics. There is a limited repertoire of antifungals in clinical use, and drug resistance and host toxicity compromise the clinical utility. The three classes of antifungals for treatment of invasive infections are the polyenes, azoles and echinocandins. Understanding mechanisms of resistance to these antifungals has been accelerated by global and targeted approaches, which have revealed that antifungal drug resistance is a complex phenomenon involving multiple mechanisms. Development of novel strategies to block the emergence of drug resistance and render resistant pathogens responsive to antifungals will be critical to treating life-threatening fungal infections.

Two clinical isolates of Candida glabrata exhibiting reduced sensitivity to amphotericin B both harbor mutations in ERG2

Two novel isolates of Candida glabrata exhibiting reduced sensitivity to amphotericin B (MIC, 8 μg ml(-1)) were found to be ERG2 mutants, wherein Δ(8)-sterol intermediates comprised >90% of the total cellular sterol fraction. Both harbored an alteration at Thr(121) in ERG2; the corresponding residue (Thr(119)) in Saccharomyces cerevisiae is essential for sterol Δ8-Δ7 isomerization. This constitutes the first report of C. glabrata harboring mutations in ERG2 and exhibiting reduced sensitivity to amphotericin B.

Regulatory circuitry governing fungal development, drug resistance, and disease

Pathogenic fungi have become a leading cause of human mortality due to the increasing frequency of fungal infections in immunocompromised populations and the limited armamentarium of clinically useful antifungal drugs. Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus are the leading causes of opportunistic fungal infections. In these diverse pathogenic fungi, complex signal transduction cascades are critical for sensing environmental changes and mediating appropriate cellular responses. For C. albicans, several environmental cues regulate a morphogenetic switch from yeast to filamentous growth, a reversible transition important for virulence. Many of the signaling cascades regulating morphogenesis are also required for cells to adapt and survive the cellular stresses imposed by antifungal drugs. Many of these signaling networks are conserved in C. neoformans and A. fumigatus, which undergo distinct morphogenetic programs during specific phases of their life cycles. Furthermore, the key mechanisms of fungal drug resistance, including alterations of the drug target, overexpression of drug efflux transporters, and alteration of cellular stress responses, are conserved between these species. This review focuses on the circuitry regulating fungal morphogenesis and drug resistance and the impact of these pathways on virulence. Although the three human-pathogenic fungi highlighted in this review are those most frequently encountered in the clinic, they represent a minute fraction of fungal diversity. Exploration of the conservation and divergence of core signal transduction pathways across C. albicans, C. neoformans, and A. fumigatus provides a foundation for the study of a broader diversity of pathogenic fungi and a platform for the development of new therapeutic strategies for fungal disease.

The increased role of non-albicans species in candidaemia: results from a 3-year surveillance study

Various studies have documented a shift in species distribution in Candida bloodstream infections (BSI), but there are little data from Southeast Asia. This study was performed to determine the species epidemiology and antifungal susceptibilities of Candida species BSI in Singapore. Candida spp. from BSI were collected from a tertiary and secondary referral hospital, and an obstetrics/paediatric hospital over a 3-year period. The most common isolates were Candida albicans (36%), Candida tropicalis (27%), Candida glabrata (16%) and Candida parapsilosis (16%). Candida parapsilosis and C. albicans were predominant in the paediatric hospital, and C. albicans and C. tropicalis predominant in the other two institutions. Candida tropicalis temporarily replaced C. albicans as the predominant strain from BSI in 2006. Overall, 87.3% of Candida isolates were susceptible to fluconazole, and 10.4% classified as susceptible-dose-dependent. Fluconazole resistance was detected in C. tropicalis (3.6%), C. parapsilosis (2.1%) and C. glabrata (4.0%). Candida albicans is the predominant species isolated from BSI in Singapore. However, non-albicans species accounted for nearly two-thirds of all cases of candidaemia and the relative increase in C. tropicalis infections deserves further investigation. Resistance to fluconazole was uncommon.

Pathogenesis and Antifungal Drug Resistance of the Human Fungal Pathogen Candida glabrata

Candida glabrata is a major opportunistic human fungal pathogen causing superficial as well as systemic infections in immunocompromised individuals and several other patient cohorts. C. glabrata represents the second most prevalent cause of candidemia and a better understanding of its virulence and drug resistance mechanisms is thus of high medical relevance. In contrast to the diploid dimorphic pathogen C. albicans, whose ability to undergo filamentation is considered a major virulence trait, C. glabrata has a haploid genome and lacks the ability to switch to filamentous growth. A major impediment for the clinical therapy of C. glabrata infections is its high intrinsic resistance to several antifungal drugs, especially azoles. Further, the development of antifungal resistance, particularly during prolonged and prophylactic therapies is diminishing efficacies of therapeutic interventions. In addition, C. glabrata harbors a large repertoire of adhesins involved in the adherence to host epithelia. Interestingly, genome plasticity, phenotypic switching or the remarkable ability to persist and survive inside host immune cells further contribute to the pathogenicity of C. glabrata. In this comprehensive review, we want to emphasize and discuss the mechanisms underlying virulence and drug resistance of C. glabrata, and discuss its ability to escape from the host immune surveillance or persist inside host cells.

Development of amphotericin B loaded polymersomes based on (PEG)(3)-PLA co-polymers: Factors affecting size and in vitro evaluation

Amphotericin B (AmB) is a broad spectrum antifungal and antileishmenial agent and its clinical use is limited due to substantial dose limiting toxicities such as nephrotoxicity. In this work, amphotericin B is formulated in polymersomes of branched (PEG)(3)-PLA co-polymer. Polymersomes were prepared by solvent injection method and the effects of various formulation and process parameters on size and size distribution were studied. The results showed that viscosity of biphasic solution during formulation has significant influence on the size and size distribution of the polymersomes. Further, drug-loaded polymersomes with size of 199.6+/-14.1nm, PDI of 0.258+/-0.18, zeta potential (zeta) of -18.07+/-4.91mV and loading of 16.26+/-2.50% were obtained. Drug was found to be intercalated in the wall of polymersomes as observed using FITC tagged drug and CLSM study. An in vitro release media containing sodium deoxycholate was developed and a significant amount of drug release was observed up to 24h there after a very slow release was obtained. Free drug was not found in the formulation and different molecular forms of the drug (AmB) were observed by UV-visible spectroscopy and circular dichroism. This was further supported by hemolysis experiments, where negligible hemolysis in the test formulation was observed as compared to 100% hemolysis in a marketed formulation (Fungizone).

Role of amphotericin B upon enhancement of protective immunity elicited by oral administration with liposome-encapsulated-Japanese encephalitis virus nonstructural protein 1 (NS1) in mice

Amphotericin B (AmB) is an antifungal antibiotic the activity of which has been associated with modulation of pro-inflammatory cytokines expression in cultured cells. Herein we reveal that co-administration with AmB enhances the immunogenicity of oral Lip-JENS1 vaccine which derived from liposomes functionalized with DSPC (distearoylphosphatidylcholine) and cholesterol (2:1, molar ratio)-bearing JE virus NS1 protein (600 microg ml(-1)). Oral single dose of Lip-JENS1 elicited a detectable serum NS1-specific IgG antibody response from a mouse model. Remarkably, the addition of AmB (125 microg per mouse), particularly, 2 h prior to, but not simultaneously with, the administration of Lip-JENS1 significantly enhanced the systemic antigen-specific antibody response, providing superior protection against lethal JEV challenges. Further, we observed AmB-induced the transcription of cytokine expression and translocation of transcriptional factor NF-kappaB from the cytoplasm to the nucleus for the murine macrophage J774A.1. Moreover, Peyer's-patch lymphocytes (PPL) from AmB-treated mice produced high levels of IL-1beta, IL-6 and TNF-alpha expression compared to the corresponding control of cells from non-treated mice. Taken together, the results suggest that AmB exerts a profound influence upon mucosal vaccination with Lip-JENS1, possibly playing an adjuvant-augmented role to "fine-tune" humoral as well as cellular immune response, thus conferring enhanced protective immunity for immunising individuals against JE infection.

Interaction of Candida albicans biofilms with antifungals: transcriptional response and binding of antifungals to beta-glucans

Candida albicans can form biofilms that exhibit elevated intrinsic resistance to various antifungal agents, in particular azoles and polyenes. The molecular mechanisms involved in the antifungal resistance of biofilms remain poorly understood. We have used transcript profiling to explore the early transcriptional responses of mature C. albicans biofilms exposed to various antifungal agents. Mature C. albicans biofilms grown under continuous flow were exposed for as long as 2 h to concentrations of fluconazole (FLU), amphotericin B (AMB), and caspofungin (CAS) that, while lethal for planktonic cells, were not lethal for biofilms. Interestingly, FLU-exposed biofilms showed no significant changes in gene expression over the course of the experiment. In AMB-exposed biofilms, 2.7% of the genes showed altered expression, while in CAS-exposed biofilms, 13.0% of the genes had their expression modified. In particular, exposure to CAS resulted in the upregulation of hypha-specific genes known to play a role in biofilm formation, such as ALS3 and HWP1. There was little overlap between AMB- or CAS-responsive genes in biofilms and those that have been identified as AMB, FLU, or CAS responsive in C. albicans planktonic cultures. These results suggested that the resistance of C. albicans biofilms to azoles or polyenes was due not to the activation of specific mechanisms in response to exposure to these antifungals but rather to the intrinsic properties of the mature biofilms. In this regard, our study led us to observe that AMB physically bound C. albicans biofilms and beta-glucans, which have been proposed to be major constituents of the biofilm extracellular matrix and to prevent azoles from reaching biofilm cells. Thus, enhanced extracellular matrix or beta-glucan synthesis during biofilm growth might prevent antifungals, such as azoles and polyenes, from reaching biofilm cells, thus limiting their toxicity to these cells and the associated transcriptional responses.

Aspergillus terreus accessory conidia are unique in surface architecture, cell wall composition and germination kinetics

Infection with Aspergillus terreus is more likely to result in invasive, disseminated disease when compared to other Aspergillus species; importantly this species appears to be less susceptible to the antifungal drug amphotericin B. Unique to this species is the ability to produce specialized structures denoted as accessory conidia (AC) directly on hyphae both in vitro and in vivo. With the hypothesis that production of AC by A. terreus may enhance virulence of this organism, we analyzed the phenotype, structure and metabolic potential of these conidia. Comparison of A. terreus phialidic conidia (conidia that arise from conidiophores, PC) and AC architecture by electron microscopy revealed distinct morphological differences between the two conidial forms; AC have a smoother, thicker outer cell surface with no apparent pigment-like layer. Further, AC germinated rapidly, had enhanced adherence to microspheres, and were metabolically more active compared to PC. Additionally, AC contained less cell membrane ergosterol, which correlated with decreased susceptibility to AMB as determined using a flow cytometry based analysis. Furthermore, AC exhibited surface patches of β1-3 glucan, suggestive of attachment scarring. Collectively, the findings of this study suggest a possible role for AC in A. terreus pathogenesis.

Antifungal drug resistance mechanisms

Antifungal resistance is a prominent feature in the management of invasive mycoses, with important implications for morbidity and mortality. Microbiological resistance, the most common cause of refractory infection, is associated with a fungal pathogen for which an antifungal MIC is higher than average or within the range designated as the resistant breakpoint. Four major mechanisms of resistance to azoles have been described in Candida spp.: decreased intracellular drug concentration by activation of efflux systems or reduction of drug penetration, modification of the target site, upregulation of the target enzyme and development of bypass pathways. Conversely, echinocandins are a poor substrate for multidrug efflux transporters, and their mechanisms of resistance are associated with point mutations and/or overexpression of FKS1 and FKS2 genes. Acquired resistance to flucytosine results from defects in its metabolism through enzymatic mutations, whereas resistance to amphotericin B may be mediated by increased catalase activity or defects in ergosterol biosynthesis.

Combination of different molecular mechanisms leading to fluconazole resistance in a Candida lusitaniae clinical isolate

We report on the underlying molecular mechanisms likely responsible for the high-level fluconazole resistance in a Candida lusitaniae clinical isolate. Fluconazole resistance correlated with overexpression of ERG11 and of several efflux pump genes, in particular, the orthologs of the Candida albicans MDR1, PDR16, CDR1, CDR2, and YOR1.

A Retrospective Analysis of Antifungal Susceptibilities of Candida Bloodstream Isolates From Singapore Hospitals

Introduction: Worldwide, Candida albicans is the most common Candida species implicated in bloodstream infections. However, the proportion of non-albicans bloodstream infections is increasing. Fluconazole resistance is known to be more common in non-albicans species, but is also reported in C. albicans. This retrospective study was performed to determine the species epidemiology of Candida bloodstream infections in Singapore hospitals, and to perform susceptibility testing to a range of antifungal drugs. Materials and Methods: Candida spp. isolated from bloodstream infections from October 2004 to December 2006 were collected from 3 participating hospitals: a tertiary referral hospital (Singapore General Hospital), a secondary referral hospital (Changi General Hospital) and an obstetrics/paediatric hospital [KK Women’s and Children’s Hospital (KKWCH)]. Isolate collection was also retrospectively extended to January 2000 for KKWCH because of the limited number of cases from this hospital. Isolates were identified by a common protocol, and antifungal susceptibility testing was performed by microbroth dilution (Sensititre One, Trek Diagnostics, United Kingdom). Results: The most common isolates were C. albicans (37%), C. tropicalis (27%) and C. glabrata (16%). There were differences in species distribution between institutions, with C. parapsilosis and C. albicans predominant in KKWCH, and C. albicans and C. tropicalis predominant in the other 2 institutions. Fluconazole resistance was detected in 3.2% of all Candida spp., and 85.3% were classified as susceptible. All C. albicans and C. parapsilosis were susceptible to fluconazole and voriconazole, while susceptibility to fluconazole was much more variable for C. glabrata and C. krusei. Conclusion: This study shows that C. albicans remains the predominant Candida species isolated from bloodstream infections in the 3 participating hospitals. However, non-albicans species accounted for nearly two-thirds of all cases of candidaemia. Resistance to fluconazole was uncommon, and was generally confined to C. krusei and C. glabrata. Key words: Antifungal agents, Antifungal drug resistance, Fungaemia

Safety, efficacy and pharmacokinetics of tuftsin-loaded nystatin liposomes in murine model

Present study was performed to evaluate the efficacy, toxicity and pharmacokinetics of antifungal drug nystatin incorporated in immunomodulator tuftsin-bearing liposomes. In vitro toxicity of free nystatin and nystatin incorporated in tuftsin-free or tuftsin-loaded liposomes was assessed by incubation of nystatin formulations with human erythrocytes. The toxicity profile of free nystatin and liposomal formulations of nystatin with or without tuftsin was also analyzed by monitoring the level of blood urea nitrogen (BUN) and serum creatinine in the treated BALB/c mice. The results of the present work showed that tuftsin-loaded nystatin liposomes like conventional nystatin liposomes exerted less toxicity to human erythrocytes as compared with free nystatin. Moreover, mice treated with tuftsin-loaded nystatin liposomes showed insignificant elevation in the biochemical values of serum creatinine and blood urea. The stability of nystatin liposomes upon incorporation of tuftsin was evaluated by monitoring the leakage of the entrapped drug in human serum. Tuftsin-loaded liposomes held nystatin for longer duration in the presence of serum than identical nystatin liposomes without tuftsin. Pharmacokinetics of the both tuftsin-free or tuftsin-loaded liposomal formulations nystatin was analyzed by determining the level of nystatin in the systemic circulation of mice at different time points. Mice injected with tuftsin-loaded nystatin liposomes showed higher level of the drug in the systemic circulation compared with those treated with conventional nystatin liposomes. The efficacy of tuftsin-loaded nystatin liposomes against A. fumigatus was evaluated by assessing the fungal burden in the lungs of treated mice. Treatment with tuftsin-loaded nystatin liposomes was most effective in eliminating fungal burden from lung tissues of infected mice compared to those treated with free nystatin or nystatin liposomes without tuftsin. The immunopotentiating activity, increased stability and less toxicity of tuftsin-incorporated nystatin liposomes, supports the idea for its prophylactic and therapeutic use in the clinical setting.

Proteomic and transcriptomic analysis of Aspergillus fumigatus on exposure to amphotericin B

Amphotericin B (AMB) is the most widely used polyene antifungal drug for the treatment of systemic fungal infections, including invasive aspergillosis. It has been our aim to understand the molecular targets of AMB in Aspergillus fumigatus by genomic and proteomic approaches. In transcriptomic analysis, a total of 295 genes were found to be differentially expressed (165 upregulated and 130 downregulated), including many involving the ergosterol pathway, cell stress proteins, cell wall proteins, transport proteins, and hypothetical proteins. Proteomic profiles of A. fumigatus alone or A. fumigatus treated with AMB showed differential expression levels for 85 proteins (76 upregulated and 9 downregulated). Forty-eight of them were identified with high confidence and belonged to the above-mentioned categories. Differential expression levels for Rho-GDP dissociation inhibitor (Rho-GDI), secretory-pathway GDI, clathrin, Sec 31 (a subunit of the exocyst complex), and RAB GTPase Ypt51 in response to an antifungal drug are reported here for the first time and may represent a specific response of A. fumigatus to AMB. The expression of some of these genes was validated by real-time reverse transcription-PCR. The AMB responsive genes/proteins observed to be differentially expressed in A. fumigatus may be further explored for novel drug development.

Potential basis for amphotericin B resistance in Aspergillus terreus

This study investigated the basis for intrinsic amphotericin B (AMB) resistance in Aspergillus terreus. The ergosterol content, cell wall composition, and lipid peroxidation level had no influence on AMB resistance. The level of catalase production in A. terreus was significantly higher than that in A. fumigatus (P < 0.05). This higher-level production may contribute to AMB resistance in A. terreus since oxidative damage has been implicated in AMB action.

Antifungal potential of disulfiram

Disulfiram, an alcohol antagonistic drug has been on the market since 1949 with 80% bioavailability and an established safety profile. Recently it has been reported as a P-glycoprotein efflux pump modulator. Herein we report its antifungal potential. The MIC50 and MIC90 of disulfiram for yeast isolates is 4 and 8 microg/ml, respectively, and the MIC range is 1-16 micro g/ml for both fluconazole sensitive and resistant strains. Interestingly, disulfiram also showed fungicidal activity on Aspergillus spp. with MIC50 and MIC90 of 2 and 8 microg/ml, respectively.

Epidemiology of invasive candidiasis: a persistent public health problem

Invasive candidiasis (IC) is a leading cause of mycosis-associated mortality in the United States. We examined data from the National Center for Health Statistics and reviewed recent literature in order to update the epidemiology of IC. IC-associated mortality has remained stable, at approximately 0.4 deaths per 100,000 population, since 1997, while mortality associated with invasive aspergillosis has continued to decline. Candida albicans remains the predominant cause of IC, accounting for over half of all cases, but Candida glabrata has emerged as the second most common cause of IC in the United States, and several less common Candida species may be emerging, some of which can exhibit resistance to triazoles and/or amphotericin B. Crude and attributable rates of mortality due to IC remain unacceptably high and unchanged for the past 2 decades. Nonpharmacologic preventive strategies should be emphasized, including hand hygiene; appropriate use, placement, and care of central venous catheters; and prudent use of antimicrobial therapy. Given that delays in appropriate antifungal therapy are associated with increased mortality, improved use of early empirical, preemptive, and prophylactic therapies should also help reduce IC-associated mortality. Several studies have now identified important variables that can be used to predict risk of IC and to help guide preventive strategies such as antifungal prophylaxis and early empirical therapy. However, improved non-culture-based diagnostics are needed to expand the potential for preemptive (or early directed) therapy. Further research to improve diagnostic, preventive, and therapeutic strategies is necessary to reduce the considerable morbidity and mortality associated with IC.

Evaluation of the antimicrobial activity of ebselen: Role of the yeast plasma membrane H+-ATPase

Ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) is a selenium-containing antioxidant demonstrating anti-inflammatory and cytoprotective properties in mammalian cells and cytotoxicity in lower organisms. The mechanism underlying the antimicrobial activity of ebselen remains unclear. It has recently been proposed that, in lower organisms like yeast, the plasma membrane H+-ATPase (Pma1p) could serve as a potential target for this synthetic organoselenium compound. Using yeast and bacteria, the present study found ebselen to inhibit microbial growth in a concentration- and time-dependent manner, and yeast and Gram-positive bacteria to be more sensitive to this action (IC50 approximately 2-5 microM) than Gram-negative bacteria (IC50 < 80 microM). Washout experiments and scanning electron microscopic analysis revealed ebselen to possess fungicidal activity. In addition, ebselen was found to inhibit medium acidification by PMA1-proficient haploid yeast in a concentration-dependent manner. Additional studies comparing PMA1 (+/-) and PMA1 (+/+) diploid yeast cells revealed the mutant to be more sensitive to treatment with ebselen than the wild type. Ebselen also inhibited the ATPase activity of Pma1p from S. cerevisiae in a concentration-dependent manner. The interaction of ebselen with the sulfhydryl-containing compounds L-cysteine and reduced glutathione resulted in the complete and partial prevention, respectively, of the inhibition of Pma1p ATPase activity by ebselen. Taken together, these results suggest that the fungicidal action of ebselen is due, at least in part, to interference with both the proton-translocating function and the ATPase activity of the plasma membrane H+-ATPase.

Phenotypic switching in Candida lusitaniae on copper sulfate indicator agar: association with amphotericin B resistance and filamentation

Candida lusitaniae is an opportunistic yeast pathogen that has the ability to develop resistance to amphotericin B (AmB). The mechanism(s) for this resistance is not well understood, although there are data supporting mutations in sterol pathways and other data supporting phenotypic switching (PS). The goal of this study was to determine whether C. lusitaniae has a PS system and to characterize any phenotypes, including any changes in AmB MICs. When 10(4) CFU of an AmB-resistant (MIC of 16 to 32 microg/ml) clinical strain was plated on yeast-peptone-dextrose (YPD) agar with 1 mM CuSO(4), three colony colors were observed: light brown (LB) >> dark brown (DB) > white (W), similar to the result for Candida glabrata. Switching did occur with high AmB resistance (MIC of 256 microg/ml) being associated with W, whereas LB and DB colonies had MICs of 2 to 8 microg/ml and 2 to 16 microg/ml, respectively. Filamentation (pseudohyphae) was associated with DB colonies. All phenotypes occurred spontaneously with greater frequency ( approximately 10(-2) to 10(-4)) than spontaneous mutations, and all phenotypes were reversible, fulfilling the two PS criteria. High AmB MICs were always associated with W colonies but not with all W colonies. Detection of PS on YPD-CuSO(4) is also similar to that in Candida glabrata, and we hypothesize that this is due to similarities in metallothionein gene expression. Phenotypic switching represents a key strategy in C. lusitaniae that confers a selective advantage during environmental challenges, including the ability to switch to AmB resistance.

Update on antifungal drug resistance mechanisms of Aspergillus fumigatus

Although the arsenal of agents with anti-Aspergillus activity has expanded over the last decade, mortality due to invasive aspergillosis (IA) remains unacceptably high. Aspergillus fumigatus still accounts for the majority of cases of IA; however less susceptible to antifungals non-fumigatus aspergilli began to emerge. Antifungal drug resistance of Aspergillus might partially account for treatment failures. Recent advances in our understanding of mechanisms of antifungal drug action in Aspergillus, along with the standardization of in vitro susceptibility testing methods, has brought resistance testing to the forefront of clinical mycology. In addition, molecular biology has started to shed light on the mechanisms of resistance of A. fumigatus to azoles and the echinocandins, while genome-based assays show promise for high-throughput screening for genotypic antifungal resistance. Several problems remain, however, in the study of this complex area. Large multicenter clinical studies--point prevalence or longitudinal--to capture the incidence and prevalence of antifungal resistance in A. fumigatus isolates are lacking. Correlation of in vitro susceptibility with clinical outcome and susceptibility breakpoints has not been established. In addition, the issue of cross-resistance between the newer triazoles is of concern. Furthermore, in vitro resistance testing for polyenes and echinocandins is difficult, and their mechanisms of resistance are largely unknown. This review examines challenges in the diagnosis, epidemiology, and mechanisms of antifungal drug resistance in A. fumigatus.

Colony morphology switching of Candida lusitaniae and acquisition of multidrug resistance during treatment of a renal infection in a newborn: case report and review of the literature

Candida lusitaniae is an emerging opportunistic pathogen which exhibits an unusual antifungal susceptibility pattern. We describe a case of fatal renal infection due to C. lusitaniae in a very low birth weight neonate who was treated with short courses of fluconazole given alternately with amphotericin B. A colony morphology switching was detected on the standard primary culture medium by changes in colony size. Switching was shown to affect deeply the susceptibility to amphotericin B. Afterwards, the switched phenotype developed a cross resistance to fluconazole and itraconazole. Several issues raised by this case are discussed in the light of an extensive review of the literature. Our observations point out the importance of both the detection of colony morphology switching and the close monitoring of antifungal susceptibility in the management of infections due to C. lusitaniae. A judicious therapeutic strategy should prevent the acquisition of multidrug resistance during antifungal therapy.

Antifungal therapy--state of the art at the beginning of the 21st century

The most relevant information on the present state of the art of antifungal chemotherapy is reviewed in this chapter. For dermatomycoses a variety of topical antifungals are available, and safe and efficacious systemic treatment, especially with the fungicidal drug terbinafine, is possible. The duration of treatment can be drastically reduced. Substantial progress in the armamentarium of drugs for invasive fungal infections has been made, and a new class of antifungals, echinocandins, is now in clinical use. The following drugs in oral and/or intravenous formulations are available: the broad spectrum polyene amphotericin B with its new "clothes"; the sterol biosynthesis inhibitors fluconazole, itraconazole, and voriconazole; the glucan synthase inhibitor caspofungin; and the combination partner flucytosine. New therapy schedules have been studied; combination therapy has found a significant place in the treatment of severely compromised patients, and the field of prevention and empiric therapy is fast moving. Guidelines exist nowadays for the treatment of various fungal diseases and maintenance therapy. New approaches interfering with host defenses or pathogenicity of fungal cells are being investigated, and molecular biologists are looking for new targets studying the genomics of pathogenic fungi.

Antifungal and antiviral chemotherapy

Fungal and viral infections are difficult to treat, since fungal infections commonly rebound after suppression by the antifungal agent and current antiviral drugs are only virustatic, allowing the virus to reassert its pathogenicity if not eliminated by the host defenses. In addition, fungal infections commonly are associated with significant biofilms, retarding drug penetration, and the fluid nature of the oral cavity does not promote drug-fungus contact for long periods of time. Both mycotic and viral pathogens are developing sophisticated methods to elude the toxic effects of drugs intended to eliminate their existence. The drug therapy of oral fungal and viral infections is therefore limited but occasionally successful (more with fungal than viral infections) and is often relegated to palliative care. The specter of drug resistance and its promotion by prolonged, repetitive and frivolous use must always be foremost in the clinician's mind.

Differential antifungal activity of isomeric forms of nystatin

When nystatin is placed in RPMI and other biological fluids, there is loss of pure nystatin, with the development of two distinguishable chromatographic peaks, 1 and 2. Peak 1 appears identical to commercially prepared nystatin. By nuclear magnetic resonance (NMR) and mass spectral analysis, peak 2 appears to be an isomer of peak 1. The isomers are quantitatively and fully interconvertible. Formation of peak 2 is accelerated at a pH of >7.0 and ultimately reaches a near 55:45 (peak 1/peak 2 ratio) mixture. We sought to determine the relative activities of peaks 1 and 2 against Candida spp. Peak 2 consistently showed higher MICs when it was the predominant form during the experiment. Time-kill analyses showed that peak 2 required > or =8 x the concentration of peak 1 to produce a modest and delayed killing effect, which was never of the same magnitude as that produced by peak 1. In both types of assays, the activity of peak 2 corresponded with intra-assay formation of peak 1. Both MIC measurements and time-kill analysis suggest that peak 2 has considerably less activity, if any at all, against Candida spp. Peak 2 may serve as a reservoir for peak 1.

Antifungal susceptibility testing: practical aspects and current challenges

Development of standardized antifungal susceptibility testing methods has been the focus of intensive research for the last 15 years. Reference methods for yeasts (NCCLS M27-A) and molds (M38-P) are now available. The development of these methods provides researchers not only with standardized methods for testing but also with an understanding of the variables that affect interlaboratory reproducibility. With this knowledge, we have now moved into the phase of (i) demonstrating the clinical value (or lack thereof) of standardized methods, (ii) developing modifications to these reference methods that address specific problems, and (iii) developing reliable commercial test kits. Clinically relevant testing is now available for selected fungi and drugs: Candida spp. against fluconazole, itraconazole, flucytosine, and (perhaps) amphotericin B; Cryptococcus neoformans against (perhaps) fluconazole and amphotericin B; and Aspergillus spp. against (perhaps) itraconazole. Expanding the range of useful testing procedures is the current focus of research in this area.

Prevalence and antifungal susceptibility of 442 Candida isolates from blood and other normally sterile sites: results of a 2-year (1996 to 1998) multicenter surveillance study in Quebec, Canada

During a 2-year surveillance program (1996 to 1998) in Quebec, Canada, 442 strains of Candida species were isolated from 415 patients in 51 hospitals. The distribution of species was as follows: Candida albicans, 54%; C. glabrata, 15%; C. parapsilosis, 12%; C. tropicalis, 9%; C. lusitaniae, 3%; C. krusei, 3%; and Candida spp., 3%. These data, compared to those of a 1985 survey, indicate variations in species distribution, with the proportions of C. glabrata and C. parapsilosis increasing by 9 and 4%, respectively, and those of C. albicans and C. tropicalis decreasing by 10 and 7%, respectively. However, these differences are statistically significant for C. glabrata and C. tropicalis only. MICs of amphotericin B were > or =4 microg/ml for 3% of isolates, all of which were non-C. albicans species. Three percent of C. albicans isolates were resistant to flucytosine (> or =32 microg/ml). Resistance to itraconazole (> or =1 microg/ml) and fluconazole (> or =64 microg/ml) was observed, respectively, in 1 and 1% of C. albicans, 14 and 9% of C. glabrata, 5 and 0% of C. tropicalis, and 0% of C. parapsilosis and C. lusitaniae isolates. Clinical data were obtained for 343 patients. The overall crude mortality rate was 38%, reflecting the multiple serious underlying illnesses found in these patients. Bloodstream infections were documented for 249 patients (73%). Overall, systemic triazoles had been administered to 10% of patients before the onset of candidiasis. The frequency of isolation of non-C. albicans species was significantly higher in this group of patients. Overall, only two C. albicans isolates were found to be resistant to fluconazole. These were obtained from an AIDS patient and a leukemia patient, both of whom had a history of previous exposure to fluconazole. At present, it appears that resistance to fluconazole in Quebec is rare and is restricted to patients with prior prolonged azole treatment.

Amphotericin B- and fluconazole-resistant Candida spp., Aspergillus fumigatus, and other newly emerging pathogenic fungi are susceptible to basic antifungal peptides

The present study shows that a number of basic antifungal peptides, including human salivary histatin 5, a designed histatin analog designated dhvar4, and a peptide from frog skin, PGLa, are active against amphotericin B-resistant Candida albicans, Candida krusei, and Aspergillus fumigatus strains and against a fluconazole-resistant Candida glabrata isolate.