Novel antifungal agents, targets or therapeutic strategies for the treatment of invasive fungal diseases: a review of the literature (2005-2009)

Synergistic and potential antifungal properties of tailored, one pot multicomponent monoterpenes co-delivered with fluconazole encapsulated nanostructure lipid carrier

Frequent and variant infections are caused by the virtue of opportunistic fungi pathogens. Candidiasis, aspergillosis, and mucormycosis are pathogenic microorganisms that give rise to vast fungal diseases that alternate between moderate to fatal in severity. The use of fluconazole as an antifungal drug was limited due to the acquired resistance in some types of Candida and other fungal species. This study aims to consolidate fluconazole's biological effectiveness against several pathogenic fungi. Six active monoterpenes (MTs) of carvacrol, linalool, geraniol, α-terpinene, citronellal, and nerolidol were selected and encapsulated in nanostructure lipid carrier (NLC) with (NLC-Flu-MTs) and/without (NLC-MTs) fluconazole in one nanoformulation to determine if they will act synergistically or not? The synthesized nanoformulation NLC-Flu-MTs and NLC-MTs exhibited very good particle size of 144.5 nm and 138.6 nm for size and zeta potential values of (- 23.5 mV) and (- 20.3 mV), respectively. Transmission electron microscope investigation confirmed that the synthesized NLCs have regular and spherical shape. The abundance and concentration of the six released monoterpenes were determined, as a novel approach, using GC-MS with very good results and validity. In-vitro antifungal screening was done before and after nano co-delivery against seven pathogenic, and aggressive fungi of Candida tropicalis, Candida krusei, Candida glabrata, Geotrichum Candidum, Candidaalbicans, Aspergillus Niger, and mucor circinelloides. Inhibition Zone diameter (IZD) and the minimum inhibitory concentration (MIC) were measured. Nanoformulations NLC-Flu-MTs and NLC-MTs manifested potential and unique biological susceptibility against all the tested microorganisms with reduced (MIC) values, especially against Candida Tropicalis (MIC = 0.97 µg/ml) which represents 16-fold of the value shown by NLC-MTs (MIC = 15.6 µg/ml) and 64-fold of fluconazole free before nanoformulation (MIC = 62.5 µg/ml). The efficiency of nanomaterials, particularly NLC-Flu-MTs, has become evident in the diminishing value of MIC which affirmed the synergism between fluconazole and the other six monoterpenes.

Metal Nanomaterials and Hydrolytic Enzyme-Based Formulations for Improved Antifungal Activity

Active research of metal-containing compounds and enzymes as effective antifungal agents is currently being conducted due to the growing antifungal resistance problem. Metals are attracting special attention due to the wide variety of ligands that can be used for them, including chemically synthesized and naturally obtained variants as a result of the so-called "green synthesis". The main mechanism of the antifungal action of metals is the triggering of the generation and accumulation of reactive oxygen species (ROS). Further action of ROS on various biomolecules is nonspecific. Various hydrolytic enzymes (glucanases and proteases), in turn, exhibit antifungal properties by affecting the structural elements of fungal cells (cell walls, membranes), fungal quorum sensing molecules, fungal own protective agents (mycotoxins and antibiotics), and proteins responsible for the adhesion and formation of stable, highly concentrated populations in the form of biofilms. A wide substrate range of enzymes allows the use of various mechanisms of their antifungal actions. In this review, we discuss the prospects of combining two different types of antifungal agents (metals and enzymes) against mycelial fungi and yeast cells. Special attention is paid to the possible influence of metals on the activity of the enzymes and the possible effects of proteins on the antifungal activity of metal-containing compounds.

Propranolol Ameliorates the Antifungal Activity of Azoles in Invasive Candidiasis

The effectiveness of current antifungal therapies is hampered by the emergence of drug resistance strains, highlighting an urgent need for new alternatives such as adjuvant antifungal treatments. This study aims to examine the synergism between propranolol and antifungal drugs, based on the premise that propranolol is known to inhibit fungal hyphae. In vitro studies demonstrate that propranolol potentiates the antifungal activity of azoles and that the effect is more pronounced for propranolol-itraconazole combination. Using an in vivo murine systemic candidemia model, we show that propranolol-itraconazole combination treatment resulted in a lower rate of body weight loss, decreased kidney fungal bioburden and renal inflammation when compared to propranolol and azole treatment alone or untreated control. Altogether, our findings suggest that propranolol increases the efficacy of azoles against C. albicans, offering a new therapeutic strategy against invasive fungal infections.

Potential Original Drug for Aspergillosis: In Vitro and In Vivo Effects of 1-N,N-Dimethylamino-5-Isocyanonaphthalene (DIMICAN) on Aspergillus fumigatus

As the recent outbreak of coronavirus disease 2019 (COVID-19) has shown, viral infections are prone to secondary complications like invasive aspergillosis with a high mortality rate, and therefore the development of novel, effective antifungals is of paramount importance. We have previously demonstrated that 1-amino-5-isocyanonaphthalene (ICAN) derivatives are promising original drug candidates against Candida strains (Patent pending), even against fluconazole resistant C. albicans. Consequently, in this study ICANs were tested on Aspergillus fumigatus, an opportunistic pathogen, which is the leading cause of invasive and systematic pulmonary aspergillosis in immunosuppressed, transplanted and cancer- or COVID-19 treated patients. We have tested several N-alkylated ICANs, a well as 1,5-naphthalene-diisocyanide (DIN) with the microdilution method against Aspergillus fumigatus strains. The results revealed that the diisocyanide (DIN) was the most effective with a minimum inhibitory concentration (MIC) value as low as 0.6 µg mL⁻¹ (3.4 µM); however, its practical applicability is limited by its poor water solubility, which needs to be overcome by proper formulation. The other alkylated derivatives also have in vitro and in vivo anti-Aspergillus fumigatus effects. For animal experiments the second most effective derivative 1-N, N-dimethylamino-5-isocyanonaphthalene (DIMICAN, MIC: 7–8 µg mL⁻¹, 36–41 µM) was selected, toxicity tests were made with mice, and then the antifungal effect of DIMICAN was tested in a neutropenic aspergillosis murine model. Compared to amphotericin B (AMB), a well-known antifungal, the antifungal effect of DIMICAN in vivo turned out to be much better (40% vs. 90% survival after eight days), indicating its potential as a clinical drug candidate.

Delivery strategies of amphotericin B for invasive fungal infections

Invasive fungal infections (IFIs) represent a growing public concern for clinicians to manage in many medical settings, with substantial associated morbidities and mortalities. Among many current therapeutic options for the treatment of IFIs, amphotericin B (AmB) is the most frequently used drug. AmB is considered as a first-line drug in the clinic that has strong antifungal activity and less resistance. In this review, we summarized the most promising research efforts on nanocarriers for AmB delivery and highlighted their efficacy and safety for treating IFIs. We have also discussed the mechanism of actions of AmB, rationale for treating IFIs, and recent advances in formulating AmB for clinical use. Finally, this review discusses some practical considerations and provides recommendations for future studies in applying AmB for combating IFIs.

Caspofungin combined with TMP/SMZ as a first-line therapy for moderate-to-severe PCP in patients with human immunodeficiency virus infection

OBJECTIVES

The effectiveness of trimethoprim/sulfamethoxazole (TMP/SMZ) for pneumocystis pneumonia (PCP) is limited with adverse events. Caspofungin, by inhibiting the cyst form of Pneumocystis jirovecii, may be an alternative therapy for PCP. However, the availability of clinical data about caspofungin combined with TMP/SMZ in the treatment of PCP in HIV-infected patients is limited. Thus, we aimed to examine the clinical effectiveness and safety of caspofungin combined with TMP/SMZ as a first-line therapy for moderate-to-severe PCP in HIV-infected patients.

METHODS

From January 2017 to December 2019, data of HIV-infected patients with moderate-to-severe PCP who received either TMP/SMZ alone or caspofungin combined with TMP/SMZ as first-line therapy were retrospectively reviewed to assess the effectiveness and safety of each regimen. The Kaplan-Meier curve and log-rank test were used for survival analysis.

RESULTS

A total of 278 patients met the criteria. The overall positive response rate of PCP treatment was 48.92%, and the overall all-cause in-hospital mortality rate was 33.09%. Patients who received combination therapy consisting of caspofungin and TMP/SMZ had a better positive response rate (59.44% vs. 37.78%, P < 0.001) and lower all-cause in-hospital mortality rate (24.48% vs. 42.22%, P = 0.003). Also, patients who received combination therapy had higher survival rate during a hospital stay (75.52% vs. 57.78%, P = 0.004), and those who received longer combination therapy were more likely to have higher survival rate (P = 0.042). We found that age (P = 0.019), CD4 cell count (P = 0.001) and therapeutic regimen (P = 0.002) were significant risk factors for all-cause in-hospital mortality rate in univariate analysis. In multivariate analysis, only CD4 cell count and therapeutic regimen were statistically significant factors associated with all-cause in-hospital mortality rate. Patients with a CD4 count of > 30 cells/µL and patients who received combination therapy consisting of caspofungin and TMP/SMZ were more likely to survive from PCP (P = 0.011 and P = 0.002, respectively). There were no additional severe adverse events caused by adding caspofungin.

CONCLUSIONS

For HIV-infected patients with moderate-to-severe PCP, combination therapy with caspofungin and TMP/SMZ is an effective and promising first-line therapy with no greater number of adverse events compared with TMP/SMZ monotherapy. Patients who received caspofungin had better positive response rates and lower all-cause in-hospital mortality rates. Also, we recommend early initiation of caspofungin.

A Biodegradable Antifungal-Loaded Sol-Gel Coating for the Prevention and Local Treatment of Yeast Prosthetic-Joint Infections

Fungal prosthetic-joint infections are rare but devastating complications following arthroplasty. These infections are highly recurrent and expose the patient to the development of candidemia, which has high mortality rates. Patients with this condition are often immunocompromised and present several comorbidities, and thus pose a challenge for diagnosis and treatment. The most frequently isolated organisms in these infections are Candida albicans and Candida parapsilosis, pathogens that initiate the infection by developing a biofilm on the implant surface. In this study, a novel hybrid organo-inorganic sol-gel coating was developed from a mixture of organopolysiloxanes and organophosphite, to which different concentrations of fluconazole or anidulafungin were added. Then, the capacity of these coatings to prevent biofilm formation and treat mature biofilms produced by reference and clinical strains of C. albicans and C. Parapsilosis was evaluated. Anidulafungin-loaded sol-gel coatings were more effective in preventing C. albicans biofilm formation, while fluconazole-loaded sol-gel prevented C. parapsilosis biofilm formation more effectively. Treatment with unloaded sol-gel was sufficient to reduce C. albicans biofilms, and the sol-gels loaded with fluconazole or anidulafungin slightly enhanced this effect. In contrast, unloaded coatings stimulated C. parapsilosis biofilm formation, and loading with fluconazole reduced these biofilms by up to 99%. In conclusion, these coatings represent a novel therapeutic approach with potential clinical use to prevent and treat fungal prosthetic-joint infections.

Intermolecular interaction energies and molecular conformations in N-substituted 4-aryl-2-methylimidazoles with promising in vitro antifungal activity

A convenient one-pot synthesis of 4-aryl-2-methyl-N-phenacylimidazoles (4) through a microwave-assisted pseudo-tricomponent reaction of α-bromoacetophenones (1) with acetamidine hydrochloride (2) is reported. Ketones (4) were successfully used as substrates for the preparation of the respective N-(2-hydroxyethyl)imidazoles (5) with yields up to 87%. The synthesized compounds were characterized by NMR and high-resolution mass spectrometry analyses, and several structures were confirmed and studied by single-crystal X-ray diffraction. The analysis of the whole-of-molecule interactions shows that, despite the difference in the atom–atom contacts forming the crystals, dispersion energies make the largest contribution to the formation of the solids, giving an isotropic tendency in the topology of the energy framework diagrams for pairs of molecules. In addition, the in vitro antifungal activity of both families of compounds [ketones (4) and alcohols (5)] against Candida albicans and Cryptococcus neoformans was evaluated, where the 2,4-dichlorophenyl-substituted alcohol (5f), an isomer of the drug miconazole, showed the highest activity (IC50 = 7.8 µg ml−1 against C. neoformans).

Biological Properties and Bioactive Components of Mentha spicata L. Essential Oil: Focus on Potential Benefits in the Treatment of Obesity, Alzheimer's Disease, Dermatophytosis, and Drug-Resistant Infections

In the present study, the medicinal aromatic plant Mentha spicata has been investigated as a source of essential oil (EO) and pharmaceuticals. The quantity and composition of EO from M. spicata cultivated in Palestine were analyzed seasonally over a three-year period. A significantly higher EO content was produced in summer and fall months (2.54–2.79%). Chemical analysis of EO revealed 31 compounds with oxygenated monoterpenes (90%) as the most abundant components followed by sesquiterpene and monoterpene hydrocarbons (6 and 3%, respectively). M spicata can be characterized as a carvone chemotype (65%). EO and carvone have shown strong inhibitory activities against the principal enzymes associated with Alzheimer's disease (AD) and overweight diseases (cholinesterase and porcine pancreatic lipase) and also shown strong antidermatophytic activity against Microsporum canis, Trichophyton rubrum, T. mentagrophytes, and Epidermophyton floccosum. The pancreatic lipase inhibition and the synergism showed the potential activity of M. spicata EO and carvone and that their combinations with standard drugs can be useful for the treatment of obesity and overweight. The results also demonstrated that, in addition to their significant inhibitory activity against biofilm formation of methicillin-resistant Staphylococcus aureus (MRSA), M. spicata EO and carvone had a strong inhibitory effect on metabolic activity and biomass of the preformed biofilm. The current study supports the utilization of M. spicata EO as a traditional medicine and opens perceptions to find more potent substances in the EO for the management of obesity, AD, and dermatophytosis and for combating drug-resistant bacterial infections.

High initial (1, 3) Beta-d-Glucan concentration may be a predictor of satisfactory response of c aspofungin combined with TMP/SMZ for HIV-negative patients with moderate to severe Pneumocystis jirovecii pneumonia

OBJECTIVES

The aim of this study was to investigate the efficacy of combination therapy of caspofungin and TMP/SMZ (trimethoprim/sulfamethoxazole) in moderate to severe pneumocystis jirovecii pneumonia (PJP) in patients without human immunodeficiency virus infection (HIV) and the relationship between therapeutic effect and plasma (1, 3) Beta-d-Glucan (BDG) levels.

METHODS

We retrospectively reviewed HIV-negative patients with PJP diagnosed in our department, who were treated with combination therapy of caspofungin and TMP/SMZ or monotherapy of TMP/SMZ during a six and a half year period.

RESULTS

A total of 126 moderate to severe PJP patients were enrolled in the study. In the multivariate analysis, low lymphocyte counts, high serum lactate dehydrogenase levels at the diagnosis of PJP and progression to shock were significant risk factors for death. In all patients, there was no significant difference in risk of death at 3 months. In the group of BDG≥800pg/m, patients receiving combination therapy was associated with a significantly decreased risk of death at 3 months, whereas in the group of BDG<800pg/ml, there were no statistically significant difference in survival rate between the two treatment regimens.

CONCLUSION

High initial plasma (1, 3) Beta-d-Glucan concentration may be a predictor of satisfactory caspofungin response to HIV-negative patients with PJP. Based on our findings, we suggest the choice of combination therapy with caspofungin and TMP/SMZ as the initial treatment when BDG≥800pg/ml in moderate to severe HIV-negative patients with PJP.

A retrospective study of patients with systemic lupus erythematosus combined with Pneumocystis jiroveci pneumonia treated with caspofungin and trimethoprim/sulfamethoxazole

Systemic lupus erythematosus (SLE) complicated with Pneumocystis jiroveci pneumonia (PCP) is a clinical complex with unsatisfying treatment efficacy and poor prognosis which is difficult to be diagnosed at early stage. The present study aimed to investigate the clinical features of SLE with PCP, recognize the early onset indicating factors, and evaluate the treatment efficacy of combined caspofungin and trimethoprim/sulfamethoxazole (coSMZ).We reviewed data of 9 patients admitted with SLE-PCP and treated with caspofungin combined with coSMZ at Tangshan Gongren Hospital from January 2013 to December 2017. Patients' clinical manifestation and laboratory data [leucocyte, lymphocyte, cluster of differentiation 4 (CD4)T cell, lactate dehydrogenase (LDH), blood gas, etc] were compared before and after treatments. And the early onset factors of SLE-PCP, treatment efficacy of combined caspofungin and CoSMZ were analyzed.Among these 9 patients, 8 patients suffered renal impairment, and all of them had been taking prednisone in the past 3 months at an average dose of 29.4 ± 13.6 mg/day. In addition, they had taken at least one kind of immunosuppressants. Laboratory data (leucocyte, lymphocyte, CD4T cell, PaO2, LDH) were remarkably abnormal at hospital admission, but they were improved significantly after 2 weeks of treatment, which is also statistically significant (P < .05), except that leukocyte had no significance change to the value at admission (P = .973). In addition, none of the studied patients died.The results of the study indicated that long-term use of glucocorticoids and immunosuppressants, low CD4T cell count, and renal impairment are the early-onset factors for SLE-PCP, caspofungin, when combined with CoSMZ, it could be a promising and effective strategy to treat SLE with PCP.

A quantitative systems pharmacology (QSP) model for Pneumocystis treatment in mice

BACKGROUND

The yeast-like fungi Pneumocystis, resides in lung alveoli and can cause a lethal infection known as Pneumocystis pneumonia (PCP) in hosts with impaired immune systems. Current therapies for PCP, such as trimethoprim-sulfamethoxazole (TMP-SMX), suffer from significant treatment failures and a multitude of serious side effects. Novel therapeutic approaches (i.e. newly developed drugs or novel combinations of available drugs) are needed to treat this potentially lethal opportunistic infection. Quantitative Systems Pharmacological (QSP) models promise to aid in the development of novel therapies by integrating available pharmacokinetic (PK) and pharmacodynamic (PD) knowledge to predict the effects of new treatment regimens.

RESULTS

In this work, we constructed and independently validated PK modules of a number of drugs with available pharmacokinetic data. Characterized by simple structures and well constrained parameters, these PK modules could serve as a convenient tool to summarize and predict pharmacokinetic profiles. With the currently accepted hypotheses on the life stages of Pneumocystis, we also constructed a PD module to describe the proliferation, transformation, and death of Pneumocystis. By integrating the PK module and the PD module, the QSP model was constrained with observed levels of asci and trophic forms following treatments with multiple drugs. Furthermore, the temporal dynamics of the QSP model were validated with corresponding data.

CONCLUSIONS

We developed and validated a QSP model that integrates available data and promises to facilitate the design of future therapies against PCP.

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

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

Efficacy of caspofungin combined with trimethoprim/sulfamethoxazole as first-line therapy to treat non-HIV patients with severe pneumocystis pneumonia

Combined treatment with caspofungin and trimethoprim/sulfamethoxazole (TMP/SMZ) as salvage therapy in non-HIV positive patients with severe pneumocystis pneumonia (PCP) yields poor outcomes. It remains unknown whether the use of this combination strategy as a first-line therapy would improve patient outcomes. The present study aimed to assess the efficacy of caspofungin combined with TMP/SMZ as a first-line therapy in non-HIV positive patients with severe PCP. A retrospective cohort study was conducted between March 2016 and February 2017. Patient clinical characteristics and outcomes were compared between two groups receiving first-line and second-line therapy respectively. In addition, similar cases from previous studies were assessed. A total of 14 patients were included in the present study (mean age, 58.79±14.41 years); including 9 patients receiving caspofungin and TMP/SMZ as a first-line therapy and 5 that received it as a second-line therapy. The overall positive response rate was 71.43% (10/14), with 88.89 (8/9) and 40.00% (2/5) in the first-line and second-line therapy groups, respectively (P=0.095). The positive response rates of patients requiring invasive mechanical ventilation differed significantly between the first-line (5/6, 83.33%) and the second-line (0/3, 0%) therapy groups (P=0.048). All-cause hospital mortality was 42.86% (6/14), with mortality rates of 33.33 (3/9) and 60.00% (3/5) in the first-line and second-line therapy groups, respectively (P=0.580). Combined with previously reported cases (n=27), the positive response rate was significantly greater in the first-line therapy group (11/12, 91.67%) than in the second-line therapy group (8/15, 53.33%, P=0.043). No significant differences were in all-cause mortality rates between the two groups (25.00 vs. 46.67%, P=0.424) were identified, despite the fact that all-course mortality in the first-line therapy group was ~50% that of the second-line therapy group. Therefore, the results of the present study indicate that combined caspofungin and TMP/SMZ as first-line therapy may be a promising and effective strategy to treat non-HIV positive patients with severe PCP, particularly for those requiring invasive mechanical ventilation.

Incidence and biodiversity of yeasts, dermatophytes and non-dermatophytes in superficial skin infections in Assiut, Egypt

OBJECTIVE

The aim was to identify the incidence of the causal agents from dermatophytes, non-dermatophytes and yeasts in Assiut Governorate employing, beside the morphological and physiological techniques, the genotypic ones.

PATIENTS

Samples from infected nails, skin and hair were taken from 125 patients.

MATERIALS AND METHODS

Patients who presented with onychomycosis, tinea capitis, tinea corporis, tinea cruris and tinea pedis during the period from February 2012 to October 2015 were clinically examined and diagnosed by dermatologists and were guided to Assiut University Mycological Centre for direct microscopic examination, culturing and identification.

RESULTS

Onychomycosis was the most common infecting (64.8% of the cases) followed by tinea capitis (17.6%). Direct microscopic preparations showed only 45 positive cases, while 96 cases showed positive cultures. Infections were more frequent in females than males. Fifty-one fungal species and 1 variety were obtained. Yeasts were the main agents being cultured from 46.02% of total cases. Non-dermatophytes were the second etiologic agents. Aspergillus was responsible for infecting 19.47% of total cases and dermatophytes appeared in only 15.93% of the cases.

CONCLUSIONS

Yeasts were the main causal agents followed by non-dermatophytic fungi (mainly species of Aspergillus, then Alternaria, Scopulariopsis and Fusarium). Both direct microscopic preparations and culturing are recommended for mycological evaluation of clinical specimens. Sequence analysis of ITS region is recommended for yeast identification.

Isolation and identification of Candida species in patients with orogastric cancer: susceptibility to antifungal drugs, attributes of virulence in vitro and immune response phenotype

Background

Because of the inherent immunosuppression of cancer patients opportunistic infections by Candida spp, occur frequently. This study aimed to identify Candida species in the oral mucosa of 59 patients with orogastric cancer (OGC) and to analyze the immunological phenotype of these patients.

Methods

The yeasts were identified by MALDI-TOF mass spectrometry (MS). For all isolates, we performed phospholipases and proteinases assays, in vitro adherence to buccal epithelial cells (BEC), minimum inhibitory concentration of antifungal drugs and determined the cytokine profile by Cytometric Bead Array flow citometry assay.

Results

C. albicans was the most prevalent species in OGC patients (51.6 %) and control group (66.7 %). Candida spp. strains isolated from OGC patients exhibited better adherence to BEC (p = 0.05) than did the control group. Phospholipases production by Candida strains from OGC patients was lower (51.6 %) than in the control group (61.9 %). Proteinases were detected in 41.9 % and 4.8 % of the yeasts from OGC patients and control group, respectively. Significant differences were found in the serum of OGC patients compared to the control group for IL-2, IL-10, TNF-α, IFN-γ and IL-17.

Conclusions

The results of this work suggest increased virulence of yeasts isolated from OGC patients and, that this may interfere with the immune phenotype.

Antifungals: Mechanism of Action and Drug Resistance

There are currently few antifungals in use which show efficacy against fungal diseases. These antifungals mostly target specific components of fungal plasma membrane or its biosynthetic pathways. However, more recent class of antifungals in use is echinocandins which target the fungal cell wall components. The availability of mostly fungistatic antifungals in clinical use, often led to the development of tolerance to these very drugs by the pathogenic fungal species. Thus, the development of clinical multidrug resistance (MDR) leads to higher tolerance to drugs and its emergence is helped by multiple mechanisms. MDR is indeed a multifactorial phenomenon wherein a resistant organism possesses several mechanisms which contribute to display reduced susceptibility to not only single drug in use but also show collateral resistance to several drugs. Considering the limited availability of antifungals in use and the emergence of MDR in fungal infections, there is a continuous need for the development of novel broad spectrum antifungal drugs with better efficacy. Here, we briefly present an overview of the current understanding of the antifungal drugs in use, their mechanism of action and the emerging possible novel antifungal drugs with great promise.

Isolation, characterization and antifungal docking studies of wortmannin isolated from Penicillium radicum

During the search for a potent antifungal drug, a cell-permeable metabolite was isolated from a soil isolate taxonomically identified as Penicillium radicum. The strain was found to be a potent antifungal agent. Production conditions of the active compound were optimized and the active compound was isolated, purified, characterized and identified as a phosphoinositide 3-kinase (PI3K) inhibitor, commonly known as wortmannin (Wtmn). This is very first time we are reporting the production of Wtmn from P. radicum. In addition to its previously discovered anticancer properties, the broad spectrum antifungal property of Wtmn was re-confirmed using various fungal strains. Virtual screening was performed through molecular docking studies against potential antifungal targets, and it was found that Wtmn was predicted to impede the actions of these targets more efficiently than known antifungal compounds such as voriconazole and nikkomycin i.e. 1) mevalonate-5-diphosphate decarboxylase (1FI4), responsible for sterol/isoprenoid biosynthesis; 2) exocyst complex component SEC3 (3A58) where Rho- and phosphoinositide-dependent localization is present and 3) Kre2p/Mnt1p a Golgi alpha1,2-mannosyltransferase (1S4N) involved in the biosynthesis of yeast cell wall glycoproteins). We conclude that Wtmn produced from P. radicum is a promising lead compound which could be potentially used as an efficient antifungal drug in the near future after appropriate structural modifications to reduce toxicity and improve stability.

Evaluation of Antifungal Activity and Mode of Action of New Coumarin Derivative, 7-Hydroxy-6-nitro-2H-1-benzopyran-2-one, against Aspergillus spp

Aspergillus spp. produce a wide variety of diseases. For the treatment of such infections, the azoles and Amphotericin B are used in various formulations. The treatment of fungal diseases is often ineffective, because of increases in azole resistance and their several associated adverse effects. To overcome these problems, natural products and their derivatives are interesting alternatives. The aim of this study was to examine the effects of coumarin derivative, 7-hydroxy-6-nitro-2H-1-benzopyran-2-one (Cou-NO₂), both alone and with antifungal drugs. Its mode of action against Aspergillus spp. Cou-NO₂ was tested to evaluate its effects on mycelia growth and germination of fungal conidia of Aspergillus spp. We also investigated possible Cou-NO₂ action on cell walls (0.8 M sorbitol) and on Cou-NO₂ to ergosterol binding in the cell membrane. The study shows that Cou-NO₂ is capable of inhibiting both the mycelia growth and germination of conidia for the species tested, and that its action affects the structure of the fungal cell wall. At subinhibitory concentration, Cou-NO₂ enhanced the in vitro effects of azoles. Moreover, in combination with azoles (voriconazole and itraconazole) Cou-NO₂ displays an additive effect. Thus, our study supports the use of coumarin derivative 7-hydroxy-6-nitro-2H-1-benzopyran-2-one as an antifungal agent against Aspergillus species.

[Microbial metabolites that inhibit sterol biosynthesis, their chemical diversity and characteristics of mode of action]

Inhibitors of sterol biosynthesis (ISB) are widespread in nature and characterized by appreciable diversity both in their chemical structure and mode of action. Many of these inhibitors express noticeable biological activity and approved themselves in development of various pharmaceuticals. In this review there is a detailed description of biologically active microbial metabolites with revealed chemical structure that have ability to inhibit sterol biosynthesis. Inhibitors of mevalonate pathway in fungous and mammalian cells, exhibiting hypolipidemic or antifungal activity, as well as inhibitors of alternative non-mevalonate (pyruvate gliceraldehyde phosphate) isoprenoid pathway, which are promising in the development of affective antimicrobial or antiparasitic drugs, are under consideration in this review. Chemical formulas of the main natural inhibitors and their semi-synthetic derivatives are represented. Mechanism of their action at cellular and biochemical level is discussed. Special attention is given to inhibitors of 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase (group of lovastatin) and inhibitors of acyl-CoA-cholesterol-acyl transferase (ACAT) that possess hypolipidemic activity and could be affective in the treatment of atherosclerosis. In case of inhibitors of late stages of sterol biosynthesis (after squalene formation) special attention is paid to compounds possessing evident antifungal and antitumoral activity. Explanation of mechanism of anticancer and antiviral action of microbial ISB, as well as the description of their ability to induce apoptosis is given.

Passive Immunization

Whereas active immunity refers to the process of exposing the individual to an antigen to generate an adaptive immune response, passive immunity refers to the transfer of antibodies from one individual to another. Passive immunity provides immediate but short-lived protection, lasting several weeks up to 3 or 4 months. Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus through the placenta or from breast milk to the gut of the infant. It can also be produced artificially, when antibody preparations derived from sera or secretions of immunized donors or, more recently, different antibody producing platforms are transferred via systemic or mucosal route to nonimmune individuals. Passive immunization has recently become an attractive approach because of the emergence of new and drug-resistant microorganisms, diseases that are unresponsive to drug therapy and individuals with an impaired immune system who are unable to respond to conventional vaccines. This chapter addresses the contributions of natural and artificial acquired passive immunity in understanding the concept of passive immunization. We will mainly focus on administration of antibodies for protection against various infectious agents entering through mucosal surfaces.

Antifungal activity of topical microemulsion containing a thiophene derivative

Fungal infections have become a major problem of worldwide concern. Yeasts belonging to the Candida genus and the pathogenic fungus Cryptococcus neoformans are responsible for different clinical manifestations, especially in immunocompromised patients. Antifungal therapies are currently based on a few chemotherapeutic agents that have problems related to effectiveness and resistance profiles. Microemulsions are isotropic, thermodynamically stable transparent systems of oil, water and surfactant that can improve the solubilization of lipophilic drugs. Taking into account the need for more effective and less toxic drugs along with the potential of thiophene derivatives as inhibitors of pathogenic fungi growth, this study aimed to evaluate the antifungal activity of a thiophene derivative (5CN05) embedded in a microemulsion (ME). The minimum inhibitory concentration (MIC) was determined using the microdilution method using amphotericin B as a control. The formulations tested (ME- blank and ME-5CN05) showed physico-chemical properties that would allow their use by the topical route. 5CN05 as such exhibited moderate or weak antifungal activity against Candida species (MIC = 270–540 μg.mL⁻¹) and good activity against C. neoformans (MIC = 17 μg.mL⁻¹). Candida species were susceptible to ME-5CN05 (70–140 μg.mL⁻¹), but C. neoformans was much more, presenting a MIC value of 2.2 μg.mL⁻¹. The results of this work proved promising for the pharmaceutical industry, because they suggest an alternative therapy against C. neoformans.

Antifungal, anti-biofilm and adhesion activity of the essential oil of Myrtus communis L. against Candida species

Candida species belong to the normal microbiota of the oral cavity, gastrointestinal tract and vagina. The increasing incidence of drug-resistant pathogens and the toxicity of the antifungal compounds have drawn the attention towards the antimicrobial activity of natural products, an inexpensive alternative. The aim of this work was to evaluate the adhesion activity, the biofilm formation and the action of the Myrtus communis L. essential oil (EO) on the biofilm formation towards three species isolated from clinical samples: Candida albicans, Candida parapsilosis and Candida tropicalis. Furthermore, we evaluated the antimycotic activity of the EO towards the three species, and the results were compared with the minimum inhibitory concentration of six antimycotics. The activity of the EO against C. albicans and C. parapsilosis was better than that obtained against C. tropicalis; moreover, the strains used in the assay were adhesive and biofilm producer, and the effect of myrtle EO on the biofilm formation yielded encouraging results.

M. Chaves M, Raposo NRB. Antifungal activity of Copaifera langsdorffii Desf oleoresin against dermatophytes

Dermatophytoses are mycoses that affect keratinized tissues in both humans and animals. The aim of this study was to investigate the antifungal activity of the oleoresin extracted from Copaifera langsdorffii Desf. against the strains Microsporum canis ATCC 32903, Microsporum gypseum ATCC 14683, Trichophyton mentagrophytes ATCC 11481 and Trichophyton rubrum CCT 5507. The antimicrobial activity was determined by minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values. Ketoconazole and terbinafine were used as reference drugs. The copaiba oleoresin showed moderate fungicidal activity against T. mentagrophytes ATCC 11481 (MIC and MFC = 170 μg mL⁻¹) and weak fungicidal activity against T. rubrum CCT 5507 (MIC = 1,360 μg mL⁻¹ and MFC = 2,720 μg mL⁻¹). There was no activity against M. canis ATCC 32903 and M. gypseum ATCC 14683. SEM analysis revealed physical damage and morphological alterations such as compression and hyphae clustering in the structure of the fungi exposed to the action of the oleoresin. The results stimulate the achievement of in vivo assays to confirm the benefits of the application of oleoresin extracted from copaiba in the treatment of dermatophytosis, both in humans and in animals.

Therapeutic potential of caspofungin combined with trimethoprim-sulfamethoxazole for pneumocystis pneumonia: a pilot study in mice

Pneumocystis pneumonia (PcP) is a major cause of mortality and morbidity in immunocompromised patients. There are limited alternative therapeutic choices to trimethoprim-sulfamethoxazole (TMP-SMX) which is the standard first line therapy/prophylaxis for PcP. The efficacy of low doses of caspofungin and caspofungin in association with TMP-SMX standard-prophylactic dose was evaluated in an experimental model of Pneumocystis. Susceptibility of Pneumocystis spp. to low doses of caspofungin and caspofungin/TMP-SMX was evaluated in Balb/c immunosuppressed mice, infected intranasally with P. murina. Caspofungin was administered once daily at 0.1 mg/kg, 0.05 mg/kg, and 0.001 mg/kg and TMP-SMX was administered by oral gavage (12.25 mg/62.5 mg/day), for 21 days. Efficacy was calculated based on the reduction in organism burden determined through quantitative fluorescent-based real-time PCR (qPCR). Serum β-1,3-D-glucan was measured as an additional marker of infection. The present data showed that caspofungin demonstrated anti-Pneumomocystis effect. However, the doses administrated were too low to achieve Pneumocystis eradication, which suggests that echinocandin treatment should not be administrated as mono-therapy. After 21 days of treatment, P. murina was not detected in the lungs of mice with either TMP-SMX or caspofungin/TMP-SMX. The results showed that, even at the lowest concentrations tested, the efficacy of caspofungin in association with TMP-SMX was higher than the efficacy of either drug used alone. The administration of caspofungin/TMP-SMX was at least 1.4 times more effective against P. murina infection than TMP-SMX used alone. The most promising result was achieved with the combination of caspofungin 0.05 mg/kg/day with TMP-SMX 12.5 mg–62.5 mg/day, which reduced the parasite burden to undetectable levels immediately at the 14^th day of treatment, showing a highly marked anti-Pneumomocystis effect. These data suggest that the administration of low doses of caspofungin in combination with low doses of TMP-SMX may provide an improved treatment protocol for Pneumocystis infection clearance.

Cryptococcosis: epidemiology, fungal resistance, and new alternatives for treatment

Cryptococcosis is an important systemic mycosis and the third most prevalent disease in human immunodeficiency virus (HIV)-positive individuals. The incidence of cryptococcosis is high among the 25 million people with HIV/acquired immunodeficiency syndrome (AIDS), with recent estimates indicating that there are one million cases of cryptococcal meningitis globally per year in AIDS patients. In Cryptococcus neoformans, resistance to azoles may be associated with alterations in the target enzyme encoded by the gene ERG11, lanosterol 14α-demethylase. These alterations are obtained through mutations, or by overexpressing the gene encoding. In addition, C. gattii and C. neoformans present a heteroresistance phenotype, which may be related to increased virulence. Other species beyond C. neoformans and C. gattii, such as C. laurentii, have been diagnosed mainly in patients with immunosuppression. Infections of C. albidus have been isolated in cats and marine mammals. Recent evidence suggests that the majority of infections produced by this pathogen are associated with biofilm growth, which is also related with increased resistance to antifungal agents. Therefore, there is a great need to search for alternative antifungal agents for these fungi. The search for new molecules is currently occurring from nanoparticle drugs of plant peptide origin. This article presents a brief review of the literature regarding the epidemiology of cryptococcosis, as well as fungal resistance and new alternatives for treatment.

Candida infections, causes, targets, and resistance mechanisms: traditional and alternative antifungal agents

The genus Candida includes about 200 different species, but only a few species are human opportunistic pathogens and cause infections when the host becomes debilitated or immunocompromised. Candida infections can be superficial or invasive. Superficial infections often affect the skin or mucous membranes and can be treated successfully with topical antifungal drugs. However, invasive fungal infections are often life-threatening, probably due to inefficient diagnostic methods and inappropriate initial antifungal therapies. Here, we briefly review our current knowledge of pathogenic species of the genus Candida and yeast infection causes and then focus on current antifungal drugs and resistance mechanisms. An overview of new therapeutic alternatives for the treatment of Candida infections is also provided.

Effect of virulence factors on the photodynamic inactivation of Cryptococcus neoformans

Opportunistic fungal pathogens may cause an array of superficial infections or serious invasive infections, especially in immunocompromised patients. Cryptococcus neoformans is a pathogen causing cryptococcosis in HIV/AIDS patients, but treatment is limited due to the relative lack of potent antifungal agents. Photodynamic inactivation (PDI) uses the combination of non-toxic dyes called photosensitizers and harmless visible light, which produces singlet oxygen and other reactive oxygen species that produce cell inactivation and death. We report the use of five structurally unrelated photosensitizers (methylene blue, Rose Bengal, selenium derivative of a Nile blue dye, a cationic fullerene and a conjugate between poly-L-lysine and chlorin(e6)) combined with appropriate wavelengths of light to inactivate C. neoformans. Mutants lacking capsule and laccase, and culture conditions that favoured melanin production were used to probe the mechanisms of PDI and the effect of virulence factors. The presence of cell wall, laccase and melanin tended to protect against PDI, but the choice of the appropriate photosensitizers and dosimetry was able to overcome this resistance.

Extracellular DNA release acts as an antifungal resistance mechanism in mature Aspergillus fumigatus biofilms

Aspergillus fumigatus has been shown to form biofilms that are associated with adaptive antifungal resistance mechanisms. These include multidrug efflux pumps, heat shock proteins, and extracellular matrix (ECM). ECM is a key structural and protective component of microbial biofilms and in bacteria has been shown to contain extracellular DNA (eDNA). We therefore hypothesized that A. fumigatus biofilms also possess eDNA as part of the ECM, conferring a functional role. Fluorescence microscopy and quantitative PCR analyses demonstrated the presence of eDNA, which was released phase dependently (8 < 12 < 24 < 48 h). Random amplification of polymorphic DNA (RAPD) PCR showed that eDNA was identical to genomic DNA. Biofilm architectural integrity was destabilized by DNase treatment. Biochemical and transcriptional analyses showed that chitinase activity and mRNA levels of chitinase, a marker of autolysis, were significantly upregulated as the biofilm matured and that inhibition of chitinases affected biofilm growth and stability, indicating mechanistically that autolysis was possibly involved. Finally, using checkerboard assays, it was shown that combinational treatment of biofilms with DNase plus amphotericin B and caspofungin significantly improved antifungal susceptibility. Collectively, these data show that eDNA is an important structural component of A. fumigatus ECM that is released through autolysis, which is important for protection from environmental stresses, including antifungal therapy.

Assessment of fungal viability after long-wave ultraviolet light irradiation combined with riboflavin administration

BACKGROUND

Corneal collagen cross-linking (CXL), a technique that combines riboflavin administration with long-wave ultraviolet light irradiation, was primarily developed to increase the biomechanical strength of collagen fibrils of the cornea to avoid the progression of keratoconus. Recently, this method has been proposed to treat selected cases of infectious keratitis.

METHODS

To test the protocol used for progressive keratoconus in infectious keratitis, Candida albicans, and Fusarium solani, strains were exposed to irradiation using a wavelength of 365 nm at a power density of 3 mW/cm(2) for 30 min in the presence of riboflavin photosensitizer. All experiments were performed in triplicate. Qualitative and quantitative measurements of fungal viability used plate cultures and an automated trypan blue dye exclusion method respectively. Fungal cell diameter was also assessed in all groups. Statistical analyses were performed using the triplicate values of each experimental condition.

RESULTS

Experimental findings of photodynamic therapy applied to the cell inactivation of both yeasts and filamentous fungi were compared with control groups. Qualitative results were corroborated with quantitative findings which showed no statistical significance between challenged samples (experimental groups) and the control group (p-value = 1). In comparison with a control group of live cells, statistical significance was observed when riboflavin solution alone had an effect on the morphologic size of filamentous fungi, while ultraviolet light irradiation alone showed a slight decrease in the cell structure of C. albicans.

CONCLUSIONS

The impact of long-wave ultraviolet combined with riboflavin photosensitizer showed no antifungal effect on C. albicans and F. solani. The significant decrease in cell morphology of both filamentous fungi and yeasts submitted to photosensitizing riboflavin and exposure to ultraviolet light, respectively, may be promising in the development and standardization of alternatives for fungal cell inactivation, because of their minimal cytotoxic effects on the corneal surface. The methodological improvement in the preparation and application of individual chemical compounds, such as riboflavin, or physical systems, such as a long-wave light source, as antifungal agents may also assist in establishing promising therapeutic procedures for keratomycosis.

Aspergillus nidulans galactofuranose biosynthesis affects antifungal drug sensitivity

The cell wall is essential for fungal survival in natural environments. Many fungal wall carbohydrates are absent from humans, so they are a promising source of antifungal drug targets. Galactofuranose (Galf) is a sugar that decorates certain carbohydrates and lipids. It comprises about 5% of the Aspergillus fumigatus cell wall, and may play a role in systemic aspergillosis. We are studying Aspergillus wall formation in the tractable model system, A. nidulans. Previously we showed single-gene deletions of three sequential A. nidulans Galf biosynthesis proteins each caused similar hyphal morphogenesis defects and 500-fold reduced colony growth and sporulation. Here, we generated ugeA, ugmA and ugtA strains controlled by the alcA(p) or niiA(p) regulatable promoters. For repression and expression, alcA(p)-regulated strains were grown on complete medium with glucose or threonine, whereas niiA(p)-regulated strains were grown on minimal medium with ammonium or nitrate. Expression was assessed by qPCR and colony phenotype. The alcA(p) and niiA(p) strains produced similar effects: colonies resembling wild type for gene expression, and resembling deletion strains for gene repression. Galf immunolocalization using the L10 monoclonal antibody showed that ugmA deletion and repression phenotypes correlated with loss of hyphal wall Galf. None of the gene manipulations affected itraconazole sensitivity, as expected. Deletion of any of ugmA, ugeA, ugtA, their repression by alcA(p) or niiA(p), OR, ugmA overexpression by alcA(p), increased sensitivity to Caspofungin. Strains with alcA(p)-mediated overexpression of ugeA and ugtA had lower caspofungin sensitivity. Galf appears to play an important role in A. nidulans growth and vigor.

Sensitization of Candida albicans biofilms to various antifungal drugs by cyclosporine A

Background

Biofilms formed by Candida albicans are resistant towards most of the available antifungal drugs. Therefore, infections associated with Candida biofilms are considered as a threat to immunocompromised patients. Combinatorial drug therapy may be a good strategy to combat C. albicans biofilms.

Methods

Combinations of five antifungal drugs- fluconazole (FLC), voriconazole (VOR), caspofungin (CSP), amphotericin B (AmB) and nystatin (NYT) with cyclosporine A (CSA) were tested in vitro against planktonic and biofilm growth of C. albicans. Standard broth micro dilution method was used to study planktonic growth, while biofilms were studied in an in vitro biofilm model. A chequerboard format was used to determine fractional inhibitory concentration indices (FICI) of combination effects. Biofilm growth was analyzed using XTT-metabolic assay.

Results

MICs of various antifungal drugs for planktonic growth of C. albicans were lowered in combination with CSA by 2 to 16 fold. Activity against biofilm development with FIC indices of 0.26, 0.28, 0.31 and 0.25 indicated synergistic interactions between FLC-CSA, VOR-CSA, CSP-CSA and AmB-CSA, respectively. Increase in efficacy of the drugs FLC, VOR and CSP against mature biofilms after addition of 62.5 μg/ml of CSA was evident with FIC indices 0.06, 0.14 and 0.37, respectively.

Conclusions

The combinations with CSA resulted in increased susceptibility of biofilms to antifungal drugs. Combination of antifungal drugs with CSA would be an effective prophylactic and therapeutic strategy against biofilm associated C. albicans infections.

Chemosensitization as a means to augment commercial antifungal agents

Antimycotic chemosensitization and its mode of action are of growing interest. Currently, use of antifungal agents in agriculture and medicine has a number of obstacles. Foremost of these is development of resistance or cross-resistance to one or more antifungal agents. The generally high expense and negative impact, or side effects, associated with antifungal agents are two further issues of concern. Collectively, these problems are exacerbated by efforts to control resistant strains, which can evolve into a treadmill of higher dosages for longer periods. This cycle in turn, inflates cost of treatment, dramatically. A further problem is stagnation in development of new and effective antifungal agents, especially for treatment of human mycoses. Efforts to overcome some of these issues have involved using combinations of available antimycotics (e.g., combination therapy for invasive mycoses). However, this approach has had inconsistent success and is often associated with a marked increase in negative side effects. Chemosensitization by natural compounds to increase effectiveness of commercial antimycotics is a somewhat new approach to dealing with the aforementioned problems. The potential for safe natural products to improve antifungal activity has been observed for over three decades. Chemosensitizing agents possess antifungal activity, but at insufficient levels to serve as antimycotics, alone. Their main function is to disrupt fungal stress response, destabilize the structural integrity of cellular and vacuolar membranes or stimulate production of reactive oxygen species, augmenting oxidative stress and apoptosis. Use of safe chemosensitizing agents has potential benefit to both agriculture and medicine. When co-applied with a commercial antifungal agent, an additive or synergistic interaction may occur, augmenting antifungal efficacy. This augmentation, in turn, lowers effective dosages, costs, negative side effects and, in some cases, countermands resistance.

Antifungal activity of eugenol analogues. Influence of different substituents and studies on mechanism of action

Twenty one phenylpropanoids (including eugenol and safrole) and synthetic analogues, thirteen of them new compounds, were evaluated for antifungal properties, first with non-targeted assays against a panel of human opportunistic pathogenic fungi. Some structure-activity relationships could be observed, mainly related to the influence of an allyl substituent at C-4, an OH group at C-1 and an OCH₃ at C-2 or the presence of one or two NO₂ groups in different positions of the benzene ring. All active compounds were tested in a second panel of clinical isolates of C. albicans and non-albicans Candida spp., Cryptococcus neoformans and dermatophytes. The eugenol derivative 4-allyl-2-methoxy-5-nitrophenol (2) was the most active structure against all strains tested, and therefore it was submitted to targeted assays. These studies showed that the antifungal activity of 2 was not reversed in the presence of an osmotic support such as sorbitol, suggesting that it does not act by inhibiting the fungal cell wall synthesis or assembly. On the other hand, the Ergosterol Assay showed that 2 did not bind to the main sterol of the fungal membrane up to 250 µg mL⁻¹. In contrast, a 22% of fungal membrane damage was observed at concentrations = 1 × MIC and 71% at 4× MIC, when 2 was tested in the Cellular Leakage assay. The comparison of log P and MICs for all compounds revealed that the antifungal activity of the eugenol analogues would not to be related to lipophilicity.

Detection of antifungal compounds in Polygonum ferrugineum Wedd. extracts by bioassay-guided fractionation. Some evidences of their mode of action

ETHNOPHARMACOLOGICAL RELEVANCE

Polygonum ferrugineum Wedd. (Polygonaceae) is used to heal infected wounds and as antiseptic, antibiotic or antifungal in the traditional Argentinean medicine. The present investigation was carried out to evaluate the antifungal properties of different extracts of aerial parts of Polygonum ferrugineum, in order to give support to its ethnopharmacological use and to isolate the compounds responsible for the antifungal properties. The most active compounds were tested for their capacity of producing hyphae malformations, similar to those previously observed for crude extracts.

MATERIALS AND METHODS

Agar Dilution Method (ADM) and Agar Overlay Bioautography (AOB) were used for bioassay-guided fractionation of the aerial part extracts against a panel of human opportunistic pathogenic fungi. The Neurospora crassa assay, followed by Optical Microscopy and Scanning Electron Microscopy observation, was used for studies of mechanisms of action.

RESULTS

MeOH extract and DCM and Hex sub-extracts, but not Aq, EtOAc or BuOH ones possess antifungal activity. Of the seven isolated compounds, cardamonin 2 showed a selective inhibition of Epidermophyton floccosum with a very low MIC (=6.2 μg/mL) and pashanone 1 possessed moderate antifungal activity (MICs=25-50 μg/mL) but a broader spectrum of action. Chalcone 2, but not 1, induced swelling and shortening of the Neurospora crassa hyphae, similar as those caused by the crude DCM extract.

CONCLUSIONS

The bioassay-guided fractionation of Polygonum ferrugineum DCM extract allowed the isolation of five active compounds. Among them, cardamonin 2 showed the highest antifungal activity and selectivity towards Epidermophyton floccosum; in addition, it induced Neurospora crassa malformations that are similar than those produced by the crude DCM extract. These results give additional support to the ethnopharmacological use of Polygonum ferrugineum as antifungal agent.

Candida biofilms and the host: models and new concepts for eradication

Biofilms define mono- or multispecies communities embedded in a self-produced protective matrix, which is strongly attached to surfaces. They often are considered a general threat not only in industry but also in medicine. They constitute a permanent source of contamination, and they can disturb the proper usage of the material onto which they develop. This paper relates to some of the most recent approaches that have been elaborated to eradicate Candida biofilms, based on the vast effort put in ever-improving models of biofilm formation in vitro and in vivo, including novel flow systems, high-throughput techniques and mucosal models. Mixed biofilms, sustaining antagonist or beneficial cooperation between species, and their interplay with the host immune system are also prevalent topics. Alternative strategies against biofilms include the lock therapy and immunotherapy approaches, and material coating and improvements. The host-biofilm interactions are also discussed, together with their potential applications in Candida biofilm elimination.

Road to clinical efficacy: challenges and novel strategies for antimicrobial peptide development

Since the discovery of magainins, cecropins and defensins 30 years ago, antimicrobial peptides (AMPs) have been hailed as a potential solution to the dearth of novel antibiotic development. AMPs have shown robust activity against a wide variety of pathogens, including drug-resistant bacteria. Unlike small-molecule antibiotics, however, AMPs have failed to translate this success to the clinic. Only the polymyxins, gramicidins, nisin and daptomycin are currently approved for medical use; the latter is the only example to have been developed in the last several decades. Nonetheless, researchers continue to isolate, modify and develop novel AMPs for therapeutic applications. Efforts have focused on increasing stability, reducing cytotoxicity, improving antimicrobial activity and incorporating AMPs in novel formulations, including nanoscale particles. As peptide synthesis and recombinant production methodologies improve, and more relevant bioassays become available, it becomes increasingly likely that AMPs will break the regulatory barrier and enter the marketplace as valuable antimicrobial weapons in the next 10 years.