Conventional Antifungals Research Articles

An insight into new strategies to combat antifungal drug resistance

Invasive fungal infections especially in immunocompromised patients represent a dominating cause of mortality. The most commonly used antifungal agents can be divided into three broad categories, including triazoles, echinocandins and polyenes. Antifungal resistance is on the increase, posing a growing threat to the stewardship of immunocompromised patients with fungal infections. The paucity of currently available antifungals leads to the rapid emergence of drug resistance and thus aggravates the refractoriness of invasive fungal infections. Therefore, deep exploration into mechanisms of drug resistance and search for new antifungal targets are required. This review highlights the therapeutic strategies targeting Hsp90, calcineurin, trehalose biosynthesis and sphingolipids biosynthesis, in an attempt to provide clinical evidence for overcoming drug resistance and to form the rationale for combination therapy of conventional antifungals and agents with novel mechanisms of action. What’s more, this review also gives a concise introduction of three new-fashioned antifungals, including carboxymethyl chitosan, silver nanoparticles and chromogranin A-N46.

Activity of anti-CR3-RP polyclonal antibody against biofilms formed by Candida auris, a multidrug-resistant emerging fungal pathogen

Fungal biofilm has remained a serious medical problem that complicates treatment of mycoses. In particular, once biofilms are formed, they display high levels of resistance against most common antifungals. Candida auris is currently considered as a serious emerging fungal pathogen frequently exhibiting high levels of resistance to antifungals. Recent studies have confirmed that C. auris shares similarity with Candida albicans in regards to virulence-associated proteins involved in adherence and biofilm development. Complement receptor 3-related protein (CR3-RP) is one of the key surface antigens expressed by Candida species during biofilm formation. Here, we have investigated the presence of this cell surface moiety on the surface of C. auris, as well as the potential of anti-CR3-RP polyclonal antibody (Ab) to inhibit biofilm formation by this emerging fungal pathogen. Using indirect immunofluorescence and ELISA, we were able to confirm the presence of CR3-RP in C. auris cells within biofilms. Further, not only anti-CR3-RP Ab was able to inhibit biofilm formation by multiple C. auris strains when added during the adherence phase, but it also demonstrated activity against C. auris 24-h pre-formed biofilms, which compared favorably to levels of inhibition achieved by treatment with current conventional antifungals fluconazole, amphotericin B, and caspofungin. Overall, our data demonstrate the presence of this antigen on the surface of C. auris and points to the potential of anti-CR3-RP Ab in eradication of biofilms formed by this novel fungal pathogen.

An ethnobotanical survey and antifungal activity of Piper guineense used for the treatment of fungal infections in West-African traditional medicine

Ethnobotanical relevancePiper guineense occurs commonly in West Africa where it is used for fungal infections instead of the costly and not always accessible conventional antifungals. Fungal, yeast-based diseases are common in West-Africa especially among those living with HIV/AIDS, and thus this study was performed in Imo state, South-Eastern Nigeria, where P. guineense is predominantly used for the treatment of fungal diseases, such as skin rashes, oral thrush and vaginosis. Aim of studyThe scarce number of previous studies on the documentation of the traditional uses of P. guineense extracts for the treatment of fungal infections in Nigeria prompted this survey. The investigation focused on how traditional healers recognize and diagnose fungal infections, how P. guineense is collected, on the various parts used for the treatments, methods of preparations, administrations and treatments. In addition, an in vitro antifungal screening of P. guineense fruit and leaf extracts of various polarities, and piperine and piperlongumine, representing the main constituents in these extracts, were performed. MethodsA house to house ethnobotanical survey was conducted using questionnaires. Twenty traditional medical practitioners (TMP) and herb sellers from ten villages were interviewed. Four human pathogenic strains of yeast and Cryptococcus neoformans, a yeast-like basidiomycete causing meningitis in immunocompromised individuals, were used for the antifungal screening. ResultsThe traditional medical practitioners (TMP) and herb sellers explained that the leaves and fruits are the most commonly used plant parts for the treatments. The oral intake of the extracts in locally produced bamboo alcohol (Kai-kai) is the most common method of administration. In accordance with these recorded traditional uses, we found that extracts of P. guineense were growth inhibitory against the fungal strains with MIC values ranging from 39 to 2500 µg/mL. The lowest MIC value of 39 µg/mL was recorded for a methanol fruit extract against Candida albicans, C. glabrata and C. tropicalis. In addition, ethanol and hexane fruit extracts were effective against the growth of C. albicans and C. glabrata, respectively, with a MIC of 78 µg/mL. Piperlongumine and piperine were active against C. albicans with MIC values of 39 and 78 µg/mL respectively. ConclusionP. guineense fruit and leaf extracts, as well as their piperamide alkaloid constituents piperine and piperlongumine, have interesting antifungal properties and could have potential as new antifungal scaffolds. Our results warrant further in-depth investigations to isolate and characterize piperamide alkaloids and other compounds responsible for the antifungal activity in the extracts.

In Vitro Characterization of a Biaryl Amide Anti-virulence Compound Targeting Candida albicans Filamentation and Biofilm Formation.

We have previously identified a small molecule compound, N-[3-(allyloxy)-phenyl]-4-methoxybenzamide (9029936), that exerts potent inhibitory activity against filamentation and biofilm formation by the Candida albicans SC5314 strain and represents a lead candidate for the development of anti-virulence approaches against C. albicans infections. Here we present data from a series of experiments to further characterize its in vitro activity and drug-like characteristics. We demonstrate the activity of this compound against a panel of C. albicans clinical isolates, including several displaying resistance to current antifungals; as well as against a set of C. albicans gain of function strains in key transcriptional regulators of antifungal drug resistance. The compound also inhibits filamentation and biofilm formation in the closely related species C. dubliniensis, but not C. glabrata or C. tropicalis. Combinatorial studies reveal the potential of compound 9029936 to be used together with currently available conventional antifungals. Results of serial passage experiments indicate that repeated exposure to this compound does not elicit resistance. Viability staining of C. albicans in the presence of high concentrations of compound 9029936 confirms that the compound is not toxic to fungal cells, and cytological staining using image flow cytometry analysis reveals that treatment with the lead compound affects hyphal length, with additional effects on cell wall and integrity of the membrane system. In vitro pharmacological profiling provides further evidence that the lead compound displays a safe profile, underscoring its excellent “drug-like” characteristics. Altogether these results confirm the potential of this compound to be further developed as a true anti-virulence agent for the treatment of C. albicans infections, including those refractory to treatment with conventional antifungal agents.

Propolis Extract for Onychomycosis Topical Treatment: From Bench to Clinic.

Onychomycosis is a chronic fungal infection of nails, commonly caused by dermatophyte fungi, primarily species of Trichophyton. Because of the limited drug arsenal available to treat general fungal infections and the frequent failure of onychomycosis treatment, the search for new therapeutic sources is essential, and topical treatment with natural products for onychomycosis has been encouraged. Propolis, an adhesive resinous compound produced by honeybees (Apis mellifera), has shown multiple biological properties including significant antifungal and anti-biofilm activities in vitro. In spite of promising in vitro results, in vivo results have not been reported so far. This study assessed an ethanol propolis extract (PE) as a topical therapeutic option for onychomycosis, including its characterization in vitro and its applicability as a treatment for onychomycosis (from bench to clinic). The in vitro evaluation included analysis of the cytotoxicity and the antifungal activity against the planktonic cells and biofilm formed by Trichophyton spp. We also evaluated the capacity of PE to penetrate human nails. Patients with onychomycosis received topical PE treatments, with a 6-month follow-up period. The results of the in vitro assays showed that PE was non-toxic to the cell lines tested, and efficient against both the planktonic cells and the biofilm formed by Trichophyton spp. The results also showed that PE is able to penetrate the human nail. The results for PE applied topically to treat onychomycosis were promising, with complete mycological and clinical cure of onychomycosis in 56.25% of the patients. PE is an inexpensive commercially available option, easy to obtain and monitor. Our results indicated that PE is a promising natural compound for onychomycosis treatment, due to its ability to penetrate the nail without cytotoxicity, and its good antifungal performance against species such as Trichophyton spp. that are resistant to conventional antifungals, both in vitro and in patients.

5-hydroxymethyl-2-furaldehyde from marine bacterium Bacillus subtilis inhibits biofilm and virulence of Candida albicans

Candida albicans is considered as the primary etiologic agent of candidiasis, a very common fungal infection in human. The yeast to hyphal transition and ability to form hypoxic biofilm on medical devices is well allied with virulence and antifungal resistance of C. albicans. Antagonistic agents that inhibit biofilm formation and alter susceptibility of C. albicans to conventional antifungals is of profound need. The present study explores the antibiofilm efficacy of Bacillus subtilis, a marine bacterial isolate from Palk Bay against C. albicans. Mass spectrometric analysis of ethyl acetate extract of B. subtilis unveiled 5-hydroxymethyl-2-furaldehyde (5HM2F) as one of its major components. 5HM2F demonstrated concentration dependent biofilm inhibition, which was also corroborated through microscopic analysis. Furthermore, 5HM2F was effective in inhibiting other virulence factors of C. albicans such as morphological transition and secreted hydrolases production. Fourier transform infrared spectroscopic analysis showed alteration in amide bond region. The reduction in ergosterol content and increased antifungal susceptibility was well allied with real time PCR result, which showed down regulation of genes involved in drug resistance mechanisms. In vivo study using Caenorhabditis elegans also substantiated the antivirulence efficacy of 5HM2F at in vivo condition. Thus, the present study reports the therapeutic potential of 5HM2F against C. albicans infections.

Healthcare workers' hands as a vehicle for the transmission of virulent strains of Candida spp.: A virulence factor approach

BackgroundAlthough the majority of Candida infections are thought to come from endogenous sources, the healthcare workers' (HCWs) hands are being increasingly reported as vehicles for the transmission of pathogens. The aim of the present study was to evaluate the susceptibility of yeast isolated from the HCWs' hands and ICU (Intensive Care Unit) surfaces to antifungal agents and to determine the virulence potential and the genetic similarity between the same. MethodsThe susceptibility of yeasts from the HCWs' hands (n = 57) and ICU surfaces (n = 98) to conventional antifungals (fluconazole, voriconazole, amphotericin B and micafungin) was evaluated using the broth microdilution assay accordance with CLSI M27-A3. Additionally, some virulence factors such as adhesion and biofilm capacity on abiotic surfaces and on endothelial cells were evaluated, as well as germ tube formation. The similarity among yeast isolates were evaluated by the RAPD technique using the P4, OPA18 and OPE18 primers. ResultsFive species of Candida were found on the HCWs' hands (C. albicans, C. parapsilosis (sensu stricto), C. glabrata, C. tropicalis and C. krusei) and two on ICU surfaces (C. albicans and C. parapsilosis (sensu stricto)). The isolates from hands had higher resistance rates, with C. glabrata having the highest indices (100% FLU; 100% MFG). The similarity of C. albicans from HCWs and ICU surfaces was ≥80% according to the three primers analyzed. Candida spp. from hands had a greater potential for adhesion and biofilm formation on abiotic surfaces (p < 0.05). C. albicans from ICU surfaces had the greatest potential of adhesion on endothelial cells after 2 and 24 h, and presented high filamentation in SEM images and formed more and larger germ tubes (p < 0.05). Conclusionthe present study showed the significant virulence potential of yeasts transmitted in the hospital environment for the first time. Additionally, healthy people working in the ICU can carry these yeasts, which are capable of surviving in hospital surfaces, on their hands, offering a risk to patients, especially those who are immunocompromised.

Clinico-mycological study of dermatophytic infections and their sensitivity to antifungal drugs in a tertiary care center.

Worldwide, dermatophytic infections are running a chronic course either due to ineffective treatment or emerging drug resistance. In the past three decades, there has been an increase in incidence and non-responsiveness to conventional antifungals, which suggests that there is a need of antifungal sensitivity testing. This study was aimed at identifying clinico-mycological pattern of dermatophytic infections in patients attending thedermatology outpatient department of a tertiary care hospital, and to obtain the sensitivity pattern of isolates against six commonly used oral antifungals (fluconazole, terbinafine, itraconazole, ketoconazole, griseofulvin and voriconazole). Patients with suspected dermatophytoses attending the outpatient department of Sir Sunderlal Hospital, Varanasi, were enrolled in the study. A detailed history, clinical examination and sample collection for mycological examinations was done. In vitro antifungal sensitivity testing was done on species isolated from culture as per the Clinical and Laboratory Standard Institute M38-A standards, with broth microdilution method. There were 256 patients recruited in the study, with a male: female ratio of 3:1. The most commonly affected age group was 20-40 years (52.4%). Tinea corporis et cruris was the most common type observed (27.2%). Potassium hydroxide positivity was seen in 211 samples (79.6%) and culture positivity was found in 139 samples (52.4%). The most common species identified was Trichophyton mentagrophytes (75.9%). Sensitivity testing was done on fifty isolates of T. mentagrophytes. Minimum inhibitory concentrations of itraconazole, ketoconazole, terbinafine and voriconazole were comparable, while griseofulvin showed the highest minimum inhibitory concentration. Itraconazole was found to be the most effective drug, followed by ketoconazole, terbinafine and fluconazole. Griseofulvin was the least effective drug among the tested antifungals. This is a hospital-based study, and may not reflect the true pattern in the community. Sensitivity pattern of only one species T. mentagrophytes was carried out. Inadequate and irregular use of antifungal drugs has led to the emergence of resistant strains, which cause poor treatment outcomes. Thus, it is very important to test for antifungal sensitivity to check for resistance to antifungals.

In vitro susceptibility of Scedosporium isolates to N-acetyl-L-cysteine alone and in combination with conventional antifungal agents.

In recent years, Scedosporium species have been more commonly recognized from severe, difficult-to-treat human infections, such as upper respiratory tract and pulmonary infections. To select an appropriate therapeutic approach for these infections is challenging, because of the commonly observed resistance of the causative agents to several antifungal drugs. Therefore, to find a novel strategy for the treatment of pulmonary Scedosporium infections the in vitro antifungal effect of a mucolytic agent, N-acetyl-L-cysteine and its in vitro combinations with conventional antifungals were investigated. Synergistic and indifferent interactions were registered in 23 and 13 cases, respectively. Antagonism was not revealed between the compounds.

Update on the Fungal Biofilm Drug Resistance and Its Alternative Treatment

Candida albicans (C. albicans) and Aspergillus fumigatus (A. fumigatus) are the two main pathogens in the clinical setting to cause serious, sometimes, lethal fungal infections. Immunocompromised patients fall victims to these fungi, with a mortality rate rising drastically over the past decades. This is in correlation with the fact that conventional antifungals are no longer capable of completely eradicating the disease, or if so, high doses are usually required to do so, leading to eventual resistance to those drugs and severe side effects. High drug resistance is in association with the discovery that these opportunistic pathogens have the ability to develop a multicellular complex, known as biofilm. Biofilms prevent drugs from reaching the fungal cells by sequestering them in their extracellular matrix. Other factors such as extracellular DNA, persister cells or heat shock protein 90 (Hsp90) also play a role in biofilm and contribute to drug recalcitrance. With the discovery of new antifungals lagging behind, scientists focused on other more profitable ways to counteract this phenomenon. Combination of two or more antifungals was found effective but came with serious drawbacks. Natural plant extracts, such as traditional Chinese medicine have also been demonstrated in vitro to possess antimicrobial actions. Great interest was directed towards their use with conventional antifungal agents with a possibility of lowering the necessary concentration required to inhibit the growth of fungi. This review aims in understanding the different factors contributing to clinical drug resistance and evaluating the effect of combination therapy and natural products on those cases difficult to treat.

Human lactoferrin triggers a mitochondrial- and caspase-dependent regulated cell death in Saccharomyces cerevisiae.

We have previously shown that the antifungal activity of human lactoferrin (hLf) against Candida albicans relies on its ability to induce cell death associated with apoptotic markers. To gain a deeper understanding of the mechanisms underlying hLf-induced apoptosis, we characterized this cell death process in the well-established Saccharomyces cerevisiae model. Our results indicate that hLf induces cell death in S. cerevisiae in a manner that requires energy and de novo protein synthesis. Cell death is associated with nuclear chromatin condensation, preservation of plasma membrane integrity, and is Yca1p metacaspase-dependent. Lactoferrin also caused mitochondrial dysfunction associated with ROS accumulation and release of cytochrome c. Pre-incubation with oligomycin, an oxidative phosphorylation inhibitor, increased resistance to hLf and, accordingly, mutants deficient in the F1F0-ATP synthase complex were more resistant to death induced by hLf. This indicates that mitochondrial energetic metabolism plays a key role in the killing effect of hLf, though a direct role of F1F0-ATP synthase cannot be precluded. Overexpression of the anti-apoptotic protein Bcl-xL or pre-incubation with N-acetyl cysteine reduced the intracellular level of ROS and increased resistance to hLf, confirming a ROS-mediated mitochondrial cell death process. Mitochondrial involvement was further reinforced by the higher resistance of cells lacking mitochondrial DNA, or other known yeast mitochondrial apoptosis regulators, such as, Aif1p, Cyc3p and Aac1/2/3p. This study provides new insights into a detailed understanding at the molecular level of hLf-induced apoptosis, which may allow the design of new strategies to overcome the emergence of resistance of clinically relevant fungi to conventional antifungals.

In vitro antifungal activity of antipsychotic drugs and their combinations with conventional antifungals against Scedosporium and Pseudallescheria isolates.

In the present study, in vitro antifungal activities of five antipsychotic drugs (i.e., chlorpromazine hydrochloride, CPZ; trifluoperazine hydrochloride, TPZ; amantadine hydrochloride; R-(-)-deprenyl hydrochloride, and valproic acid sodium salt) and five conventional antifungal drugs (i.e., amphotericin B, AMB; caspofungin, CSP; itraconazole; terbinafine, TRB and voriconazole, VRC) were investigated in broth microdilution tests against four clinical and five environmental Scedosporium and Pseudallescheria isolates. When used alone, phenothiazines CPZ and TPZ exerted remarkable antifungal effects. Thus, their in vitro combinations with AMB, CSP, VRC, and TRB were also examined against the clinical isolates. In combination with antifungal agents, CPZ was able to act synergistically with AMB and TRB in cases of one and two isolates, respectively. In all other cases, indifferent interactions were revealed. Antagonism was not observed between the tested agents. These combinations may establish a more effective and less toxic therapy after further in vitro and in vivo studies for Scedosporium and Pseudallescheria infections.

Activity of Novel Synthetic Peptides against Candida albicans.

Candida spp. are the most common causes of fungal infections worldwide. Among the Candida species, Candida albicans remains the predominant species that causes invasive candidiasis in most countries. In this study, we used two peptides, KABT-AMP and uperin 3.6 as templates to develop novel antifungal peptides. Their anticandidal activity was assessed using a combination of MIC, time-killing assay and biofilm reduction assay. Hybrid peptides, KU2 and KU3 containing a mixed backbone of KABT-AMP and Uperin 3.6 demonstrated the most potent anticandidal activity with MIC values ranging from 8–16 mg/L. The number of Trp residues and the amphipathic structure of peptides probably enhanced the anticandidal activity of peptides. Increasing the cationicity of the uperin 3.6 analogues resulted in reduced MIC from the range of 64–128 mg/L to 16–64 mg/L and this was also correlated with the antibiofilm activity and killing kinetics of the peptides. Peptides showed synergistic effects when used in combination with conventional antifungals. Peptides demonstrated low haemolytic activity but significant toxicity on two normal human epithelial cell lines. This study provides us with a better understanding on the structure-activity relationship and the balance between cationicity and hydrophobicity of the peptides although the therapeutic application of the peptides is limited.

Synergistic fungicidal activity of the lipopeptide bacillomycin D with amphotericin B against pathogenic Candida species.

In the present study, the synergism of the lipopeptide bacillomycin D in combination with the polyene amphotericin B against pathogenic Candida species is described along with their potential cytotoxicity against mammalian cells. Bacillomycin D inhibited the growth of various Candida species at minimal concentrations from 12.5 to 25 μgml(-1). Furthermore, it showed a synergistic effect with the antifungal drug amphotericin B in inhibiting the growth of Candida strains, with fractional inhibitory concentration indices ranging from 0.28 to 0.5. Time killing studies revealed a >2-log reduction in the viability of Candida albicans ATCC 10231 cells after 3 h incubation with the combination amphotericin B plus bacillomycin D, at their subinhibitory concentration. Interestingly, when the two drugs were used together at those dosages displaying a synergism in the anti-Candida activity, no cytotoxic effect was observed against mammalian cells. Therefore, the combination bacillomycin D/amphotericin B may represent a valid alternative to conventional antifungals for topical treatment of C. albicans infections. To the best of our knowledge, this is the first report describing the in vitro interaction between the antifungal drug amphotericin B and bacillomycin D against pathogenic Candida species.

Calcium signaling mediates antifungal activity of triazole drugs in the Aspergilli

Azoles are widely applied and largely effective as antifungals; however, the increasing prevalence of clinically resistant isolates has yet to be matched by approaches to improve the efficacy of antimicrobial therapy. In this study, using the model fungus Aspergillus nidulans and one of the most common human pathogen Aspergillus fumigatus as research materials, we present the evidence that calcium signaling is involved in the azole-antifungals-induced stress-response reactions. In normal media, antifungal-itraconazole (ITZ) is able to induce the [Ca2+]c increased sharply but the addition of calcium chelator-EGTA or BAPTA almost blocks the calcium influx responses, resulted in the dramatically decreasing of [Ca2+]c transient. Real-time PCR analysis verified that six-tested Ca2+-inducible genes—two calcium channels (cchA/midA), a calmodulin-dependent phosphatase-calcineurin (cnaA), a transcription factor-crzA, and two calcium transporters (pmrA/pmcA)—could be transiently up-regulated by adding ITZ, indicating these components are involved in the azole stress-response reaction. Defect of cnaA or crzA caused more susceptibility to azole antifungals than did single mutants or double deletions of midA and cchA. Notably, EGTA may influence Rh123 accumulation as an azole-mimicking substrate through the process of the drug absorption. In vivo studies of a Galleria mellonella model identified that the calcium chelator works as an adjunct antifungal agent with azoles for invasive aspergillosis. Most importantly, combination of ITZ and EGTA or ITZ with calcium signaling inhibitor-FK506 greatly enhances the ITZ efficacy. Thus, our study provides potential clues that specific inhibitors of calcium signaling could be clinically useful adjuncts to conventional azole antifungals in the Aspergilli.

Synthesis and anti-yeast evaluation of novel 2-alkylthio-4-chloro-5-methyl-N-[imino-(1-oxo-(1H)-phthalazin-2-yl)methyl]benzenesulfonamide derivatives.

Pathogenic fungi are one of the main causes of hospital-related infections. Since conventional antifungals have become less effective because of the increasing fungal resistance to the standard drugs, the need for new agents is becoming urgent. Herein we report a synthesis of a series of novel N-[imino-(1-oxo-(1H)-phthalazin-2-yl)methyl]-benzenesulfonamide derivatives with in vitro activity against yeast-like fungi isolated from the oral cavity and respiratory tract of patients with candidiasis. These compounds were synthesized by the one-step or two-step reactions of 1-(2-alkylthiobenzensulfonyl)-2-aminoguanidines with the appropriate ortho-carbonyl benzoic acids. The biological study revealed that new derivatives have shown significant growth-inhibitory activity, superior or comparable, than those of the reference drug fluconazole. The most promising activities were observed against Candida albicans, with inhibition at least 1–3 (12.5%–37.5%) of the eight tested strains at the low MIC level of ≤6.2–25 µg/mL.

In Vitro Effect of Amphotericin B on Candida albicans, Candida glabrata and Candida parapsilosis Biofilm Formation

Candida spp. biofilm is considered highly resistant to conventional antifungals. The aim of this study was to investigate the in vitro effect of amphotericin B on Candida spp. biofilms at different stages of maturation. We investigated the activity of amphotericin B against 78 clinical isolates of Candida spp., representing three species, growing as planktonic and sessile cells, by a widely accepted broth microdilution method. The in vitro effect on sessile cell viability was evaluated by MTT reduction assay. All examined strains were susceptible to amphotericin B when grown as free-living cells. At the early stages of biofilm maturation 96.7-100.0 % strains, depending on species, displayed amphotericin B sessile minimal inhibitory concentration (SMIC) ≤ 1 μg/mL. Mature Candida spp. biofilm of 32.1-90.0 % strains displayed amphotericin B SMIC ≤ 1 μg/mL. Based on these results, amphotericin B displays species- and strain-depending activity against Candida spp. biofilms.

Antimicrobial activity of aurein 2.5 against yeasts

Fungal infections with multiple resistance to conventional antifungals are increasingly becoming a medical problem, and there is an urgent need for new antifungal compounds with novel mechanisms of action. Here, we show that aurein 2.5, a naturally occurring peptide antibiotic, displays activity against the fungal strains: Rhodotorula rubra and Schizosaccharomyces pombe (MICs <130μM). The peptide adopted high levels of membrane-interactive α-helical structure (>65%) in the presence of lipid membranes derived from these organisms and showed strong propensities to penetrate (π≥13mNm(-1) ) and lyse them (>70%). Based on these data, we suggest that aurein 2.5 kills yeasts via membranolytic mechanisms and may act as a template for the development of therapeutically useful antifungal agents.

Mechanism of action of novel synthetic dodecapeptides against Candida albicans

BackgroundThree de novo designed low molecular weight cationic peptides (IJ2, IJ3 and IJ4) containing an unnatural amino acid α,β-didehydrophenylalanine (∆Phe) exhibited potent antifungal activity against fluconazole (FLC) sensitive and resistant clinical isolates of Candida albicans as well as non-albicans and other yeast and filamentous pathogenic fungi. In the present study, their synthesis, susceptibility of different fungi and the mechanism of anti-candidal action have been elucidated. MethodsThe antimicrobial peptides (AMPs) were synthesized by solid-phase method and checked for antifungal activity against different yeasts and fungi by broth microdilution method. Anti-candidal mode of action of the peptides was investigated through detecting membrane permeabilization by confocal microscopy, Reactive Oxygen Species (ROS) generation by fluorometry, apoptosis and necrosis by flow cytometry and cell wall damage using Scanning and Transmission Electron Microscopy. Results and conclusionsThe MIC of the peptides against C. albicans and other yeast and filamentous fungal pathogens ranged between 3.91 and 250μM. All three peptides exhibited effect on multiple targets in C. albicans including disruption of cell wall structures, compromised cell membrane permeability leading to their enhanced entry into the cells, accumulation of ROS and induction of apoptosis. The peptides also showed synergistic effect when used in combination with fluconazole (FLC) and caspofungin (CAS) against C. albicans. General significanceThe study suggests that the AMPs alone or in combination with conventional antifungals hold promise for the control of fungal pathogens, and need to be further explored for treatment of fungal infections.

A non‐fatal case of invasive zygomycete (Lichtheimia corymbifera) infection in an allogeneic haematopoietic cell transplant recipient

Post-transplant infections in allogeneic haematopoietic cell transplant (allo-HCT) recipients often have severe consequences. This is especially the case when dealing with zygomycete infections where the result is often fatal. A major problem when dealing with zygomycete infections is the need for an accurate and fast diagnosis as the phylum is highly resistant towards the conventional antifungals. We herein describe a non-fatal case of Lichtheimia corymbifera infection in an allo-HCT recipient.