Abstract Background EL219 is a novel polyene antifungal drug (formerly known as SF001) currently in preparation for Phase 2 clinical trials (Elion Therapeutics). Through synthetic modifications to amphotericin B, EL219 was designed to improve antifungal activity while reducing the potential for toxicity. This international surveillance study reports on the in vitro activity of EL219 and amphotericin B tested against contemporary Candida and Aspergillus clinical isolates. Methods 130 Candida and 265 Aspergillus isolates were collected in 2024 from 73 medical centers worldwide including: USA (n=118, 25 centers), Europe (n=190, 17 countries), Asia-Pacific (n=75, 6 countries), and Latin America (n=12, 5 countries). Isolates were tested for susceptibility by CLSI broth microdilution methods. MIC results for comparator agents were interpreted per CLSI guidelines. Results EL219 was active against all Aspergillus species with MIC90 values ranging from 0.25-1 µg/mL; A. fumigatus (n=157; MIC50/90, 0.5/1 µg/mL), A. flavus species complex (sc) (n=32; MIC50/90, 0.5/0.5 µg/mL), A. niger sc (n=57; MIC50/90, 0.25/0.25 µg/mL), other Aspergillus species (n=19; MIC50/90, 0.5/1 µg/mL). EL219 was more active in vitro than amphotericin B against all Aspergillus species groups whose MIC90 values ranged from 0.5-4 µg/mL. EL219 was also active against all Candida species with MIC90 values ranging from 0.25-1 µg/mL; C. albicans (n=36; MIC50/90, 0.12/0.25 µg/mL), C. auris (n=31; MIC50/90, 0.25/1 µg/mL), C. glabrata (n=28; MIC50/90, 0.12/0.25 µg/mL), C. parapsilosis (n=16; MIC50/90, 0.12/0.25 µg/mL), and other Candida species (n=19; MIC50/90, 0.12/0.25 µg/mL). EL219 was more active in vitro than amphotericin B against all Candida species groups whose MIC90 values ranged from 1-2 µg/mL. Conclusion EL219 was active against prevalent Aspergillus and Candida clinical isolates causing invasive mycoses recovered in 2024. EL219 was often 4- to 8-fold more active than amphotericin B when comparing MIC50/90 values. These results further support the continued development of EL219. Disclosures Mariana Castanheira, PhD, Melinta Therapeutics: Advisor/Consultant|Melinta Therapeutics: Grant/Research Support

Amphotericin: B (AmpB)-resistant Candida (C.) species, such as C. parapsilosis, are among the most common causes of invasive fungal infections, posing significant challenges in hospital settings. Although AmpB is considered the first-line treatment owing to its broad-spectrum fungicidal activity, its use is hampered by severe side effects and the emergence of acquired resistance, particularly in C. parapsilosis, which exhibits reduced susceptibility to polyene, azole, and echinocandin-based antifungal drugs. Here, we present findings on photodynamic therapy (PDT) that targets the opportunistic fungal pathogens C. parapsilosis and C. albicans via the use of photosensitizers from the iodocyanine and newly developed iodinated Methylene blue families. These compounds contain heavy iodine atoms that increase the production of reactive oxygen species (ROS), the agents responsible for oxidative cellular damage, via the heavy-atom effect, which promotes intersystem crossing (ISC) and triplet-state formation. A strong antifungal effect was observed against AmpB-resistant C. parapsilosis, indicating a correlation between the quantum yield of ROS generation and the photosensitizing efficacy under near-infrared (NIR) light irradiation. The combination of efficient cellular uptake and enhanced ROS generation positions iodinated photosensitizers as promising candidates for the treatment of drug-resistant Candida strains.

This study presents a model investigation into the development of tolerance to polyene antifungal drugs (nystatin and natamycin) in strains of Malassezia pachydermatis. This species, commonly associated with external ear canal infections in dogs, has emerged as increasingly significant in the broader context of growing fungal resistance to treatment. In the experiment, 10 strains of M. pachydermatis were passaged over a period of 105 weeks on media containing sublethal concentrations of nystatin and natamycin. Minimal inhibitory (MIC) and minimal fungicidal concentration (MFC) values were regularly assessed to monitor tolerance development. The results revealed a varied response among the strains: Some were eliminated during the process, while others showed a gradual increase in MIC values, up to fivefold in the case of nystatin. In several strains, acquired resistance remained stable even after passaging in drug-free conditions, whereas others reverted to their original susceptibility. The model demonstrated that resistance does not emerge immediately; significant changes appeared only after 30–45 passages. The authors propose this model as a valuable tool for tracking sequential changes that lead to resistance development. Such an approach may support targeted therapy development and help identify strains predisposed to drug adaptation. These findings hold promise for assessing therapeutic risk in immunosuppressed patients and for building resistance datasets that can support artificial intelligence algorithms in predicting fungal resistance mechanisms.

Bacillus bacteria are often used in the production of biopreparations. Moreover, these bacteria can be used in agriculture as probiotics or starters for manufacturing fodder preserved by fermentation (silage). The ability of Bacillus bacteria to produce many biologically active molecules and metabolites with antimicrobial activity means that these bacteria can stimulate plant growth and restore the balance of the microbiome in the digestive system of certain animals. Using molecular biological analysis, bioinformatic annotation, and metabolic profiling of whole genome sequences, we analyzed two promising candidates for creating biopreparations, i.e., two Bacillus strains, namely B. mucilaginosus 159 and B. subtilis 111. We compared the genomes of these two strains and characterized both their microbiomic and metabolomic features. We demonstrated that both strains lacked elements contributing to the formation of toxic and virulent properties; however, both exhibited potential in the biosynthesis of B vitamins and siderophores. Additionally, these strains could synthesize many antimicrobial substances of different natures and spectrums of action. B. mucilaginosus 159 could synthesize macrolactin H (an antibiotic from the polyketide group), mersacidin (a class II lanthipeptide), and bacilysin. Meanwhile, B. subtilis 111 could synthesize andalusicin (a class III lanthipeptide), bacilysin, macrolactin H, difficidin, bacillaene (a polyene antibiotic), fengycin (a lipopeptide with antifungal activity), and surfactin (another lipopeptide). Further, a unique pathway of intracellular synthesis of the osmoprotectant glycine betaine was identified in B. subtilis 111, with the participation of betaine aldehyde dehydrogenase (BetB); this is not widely represented in bacteria of the genus Bacillus. These compounds can increase osmotic stability, which may be key for manufacturing biological starters for silage preparation. These two Bacillus strains are safe for use as probiotic microorganisms or starters in producing preserved fodder. However, B. subtilis 111 may be preferable due to a wider spectrum of synthesized antimicrobial substances and vitamins. Our findings exemplify using genomic technologies to describe the microbiomic and metabolomic characteristics of significant bacterial groups such as Bacillus species.

The paper presents the results of an in-depth spectroscopic, theoretical (quantum chemical), and microbiological study conducted on a promising, synergistic composition of a newly considered 1,3,4-thiadiazole derivative, 1,3,4-thiadiazole: 2,4-dihydroxy-N-(5-methyl-1,3,4-thiadiazol-2-yl)-benzothioamide (TBTA), and the "gold standard" polyene antibiotic, amphotericin B (AmB). The spectroscopic properties of the system were extensively analyzed with a range of spectroscopic measurement techniques, including electronic fluorescence and absorption spectra, resonance light scattering measurements, circular dichroism spectra, dynamic light scattering, and fluorescence anisotropy, which were further complemented with time-resolved measurements of fluorescence lifetimes performed with the single-photon counting method. The samples were prepared in DMSO solutions and/or PBS buffer to facilitate observation of the monomeric, dimeric, and aggregated forms of the antibiotic previously identified in the literature. Absorption and fluorescence emission spectra measured for AmB and the synergistic composition revealed differences that indicated changes in AmB aggregation molecules, particularly in the buffer medium. Together with the results of the other spectroscopic techniques and computations, the effects of AmB disaggregation are clearly observed, and it is seen that TBTA interacts with AmB at the sites where other AmB molecules prefer to interact with it. We also present the first biological analysis of this TBTA/AmB composition, and it confirms the synergistic effects of TBTA. The report provides a detailed description of the synergism observed between a newly synthesized derivative from the group of 1,3,4-thiadiazoles (TBTA) and the antibiotic AmB, an effect that may prove to be very significant in the context of the ongoing efforts to identify new substances with antifungal properties.

BackgroundDisaccharide polyene macrolides exhibit superior water solubility and significantly reduced hemolytic toxicity compared to their monosaccharide counterparts, making them promising candidates for safer antifungal therapeutics. In this study, we engineered a Streptomyces gilvosporeus (pSET152-nppY) capable of producing disaccharide-pimaricin (DSP) through heterologous expression of the nppY gene, which encodes a glycosyltransferase responsible for the second sugar extension in the biosynthetic pathway.ResultsThe novel compound was structurally characterized and designated disaccharide-pimaricin (DSP), featuring an aglycone identical to pimaricin and a unique disaccharide moiety (mycosaminyl-α1–4-N-acetylglucosamine). A purification protocol for DSP was established. Compared to pimaricin, DSP demonstrated a 50% reduction in antifungal activity, a 12.6-fold decrease in hemolytic toxicity, and a remarkable 107.6-fold increase in water solubility. Growth analysis revealed a delayed growth cycle in the mutant strain, suggesting that nppY expression may impose additional metabolic burden. Optimization of the fermentation medium using a statistical design identified an optimal formulation, with a maximum DSP titer of 138.168 mg/L.ConclusionsThis study underscores the potential of disaccharide polyene macrolides as safer antifungal agents and establishes a robust framework for engineering strains to produce these compounds. The findings provide critical insights into balancing biosynthetic efficiency and strain fitness, advancing the development of next-generation polyene antibiotics.

Background/Objectives: pentane polyene antibiotic Roseofungin produced by actinomycetes possessing wide range of antimicrobial activity. Methods: The structure of novel polyene antibiotic Roseofungin was confirmed through FTIR, H1 nuclear magnetic resonance, and high-performance liquid chromatography analysis with a mass detector. The substance pharmaco-technological parameters were evaluated. Additionally, the in silico modelling of various physicochemical parameters and biological activities was performed using validated open-access software tools such as ProTox3, SwissADME, and ADMET SAR1. The evaluation of its toxicological profile was also investigated in vivo. Results: The Roseofungin exhibits potential risks in certain categories, including immunotoxicity, respiratory toxicity, and nephrotoxicity, as predicted in silico. However, Roseofungin shows a relatively safe profile with regard to hepatotoxicity, neurotoxicity, and mutagenicity, along with lower risks of carcinogenicity and cytotoxicity in silico. The analysis of body weight dynamics after Roseofungin exposure in mice revealed no statistically significant differences among the experimental groups. Similarly, in the absolute or relative weights of internal organs across the experimental groups after Roseofungin treatment, no significant differences were observed in vivo. Roseofungin appears as a light-yellow hygroscopic powder with a specific odour, possessing the ability to settle and classified as a light powder. The particles are lamellar crystals ranging in size from 3 μm to 6 μm, and the molecules generate electrostatic tension between themselves. The pharmaco-technological parameters of Roseofungin were comprehensively studied. Conclusions: The experimental data obtained provide a foundation for further pharmaceutical development of new drugs containing the original Roseofungin.

The global spread of multidrug-resistant pathogenic fungi presents a serious threat to human health, necessitating the discovery of antifungals with unique modes of action1. However, conventional activity-based screening for previously undescribed antibiotics has been hampered by the high-frequency rediscovery of known compounds and the lack of new antifungal targets2. Here we report the discovery of a polyene antifungal antibiotic, mandimycin, using a phylogeny-guided natural-product discovery platform. Mandimycin is biosynthesized by the mand gene cluster, has evolved in a distinct manner from known polyene macrolide antibiotics and is modified with three deoxy sugars. It has demonstrated potent and broad-spectrum fungicidal activity against a wide range of multidrug-resistant fungal pathogens in both in vitro and in vivo settings. In contrast to known polyene macrolide antibiotics that target ergosterol, mandimycin has a unique mode of action that involves targeting various phospholipids in fungal cell membranes, resulting in the release of essential ions from fungal cells. This unique ability to bind multiple targets gives it robust fungicidal activity as well as the capability to evade resistance. The identification of mandimycin using the phylogeny-guided natural-product discovery strategy represents an important advancement in uncovering antimicrobial compounds with distinct modes of action, which could be developed to combat multidrug-resistant fungal pathogens.

Invasive fungal infections have been an increasingly global issue with high mortality. Amphotericin B (AmB), as the "gold standard" antifungal drug, has broad-spectrum antifungal activity and low clinical resistance. Therefore, AmB is the most commonly used polyene antibiotic for the treatment of invasive fungal infections. However, the serious side effects as well as the low bioavailability of AmB strongly restrict its clinical applications. Polymer, with its diversified molecular design, is widely used in drug delivery in the form of polymeric prodrugs, nanoparticles, hydrogels, etc. Therefore, polymers hold great promise for the delivery of AmB in treating fungal infections. This review summarizes recent advances in polymer-based delivery systems of AmB for the treatment of fungal infections, including polymer-AmB conjugates, nanotechnology-based polymeric delivery systems, hydrogels, and polymeric microneedles. Taking advantage of polymer-based delivery strategies, special attention is paid to reducing the side effects and improving the bioavailability of AmB for safe and effective antifungal therapy. Finally, the limitations and possible future directions of polymer-based AmB delivery systems are discussed.

Natamycin is a polyene macrocyclic antibiotic extensively used in food, medical, and agricultural industries. However, its high production cost and low synthetic efficiency fail to meet the growing market demand. Therefore, enhancing the production of natamycin-producing strains is crucial for achieving its industrial-scale production. This study systematically evaluated 16 mutagenesis methods and identified atmospheric and room temperature plasma mutagenesis combined with 2-deoxyglucose tolerance screening as the optimal strategy for enhancing natamycin production. A high-yield mutant strain, AG-2, was obtained, achieving an 80% increase in natamycin production (1.53 g/L) compared to the original strain. Metabolic analysis revealed that glycolysis and the pentose phosphate pathway were enhanced in AG-2, while the tricarboxylic acid cycle was weakened, significantly increasing the supply of precursors such as acetyl-CoA, methylmalonyl-CoA, and the reducing power of NADPH. Additionally, overexpression of the nitrogen metabolism regulatory gene glnR promoted the supply of glutamate and glutamine, further increasing natamycin production in AG-2 to 1.85 g/L. In a 5 L fermenter, the engineered strain AG-glnR achieved a final natamycin production of 11.50 g/L, 1.67 times higher than the original strain. This study is the first to combine mutagenesis with nitrogen metabolism regulation, effectively enhancing natamycin production and providing a novel approach for the efficient synthesis of other polyene antibiotics.

Pimaricin (PMR) is a polyene antifungal drug commonly used as the primary medicine for treating fungal keratitis. In this study, a selective and novel spectrofluorimetric method was designed, optimized, and validated to determine pimaricin in its ophthalmic preparations. The method based on the formation of a nitrobenzoxadiazole-based yellow fluorophore upon the reaction of pimaricin with 4-chloro-7-nitro-1,2,3-benzoxadiazole (NBD-Cl). The fluorescence intensity of the fluorophore was measured at the emission wavelength of 538.5 nm (excitation = 473.5 nm). The factors affecting the reaction (reagent volume, alkalinity, reaction temperature, heating time, volume and type of buffer solution, and the dilution solvent) were investigated and optimized. The calculated linear range was 0.25–1.5 µg/mL, and the limits of detection and quantitation for the method were 0.047 and 0.143 µg/mL, respectively. The selectivity of the method for PMR in the presence of the pharmaceutical additive benzalkonium chloride was proved. The established method was successfully applied to determine PMR in its pharmaceutical ophthalmic preparation (Natamycin® ophthalmic drops) with an accuracy of 103.79 ± 1.83%. The proposed method is practical and valuable for its routine application in quality control laboratories for analysis of PMR in its ophthalmic pharmaceutical preparation.

Cryptococcal meningitis is an alarming fungal infection that usually affects the meninges surrounding the brain and spinal cord. The causative organism is Cryptococcus neoformans. Although this infection can occur in normal individuals, it is more often seen in patients with human immunodeficiency virus/acquired immunodeficiency syndrome. Amphotericin B is an antifungal medication often used to treat severe fungal infections. It belongs to the class of polyene antifungal drugs, and it acts by binding to the cell membrane of the fungus. This causes some essential cellular components to leak out and ultimately the fungus dies. However, the administration of Amphotericin B is associated with toxicity. Therefore, lipid formulations are preferred to decrease the toxicity and increase the therapeutic index of the drug. It is widely used since it has a longer tissue half-life, the drug induced toxic effects are lower and it can penetrate the brain tissue efficaciously. This review collects and analyzes several research studies and literature reviews found in the electronic databases. The inclusion criteria prioritize studies focusing on the efficacy and drawbacks of using liposomal Amphotericin B as a treatment for fungal meningitis. In conclusion, liposomal Amphotericin B showed more effective treatment compared to other available antifungal drugs. Patients treated with a single dose of liposomal Amphotericin B coupled with fluconazole and flucytosine exhibited fewer adverse events and the mortality rate was also lower as compared to the control group.

Objectives: In 2022, the World Health Organization highlighted the necessity for the development of new antifungal agents. Polyene antibiotics are characterized by a low risk of drug resistance; however, their use is limited by low solubility and severe side effects. Methods: A series of N-alkylated derivatives of amphotericin B and nystatin A1 as well as their N-(2-hydroxyethyl)amides were synthesized. Their antifungal activity was evaluated against various Candida strains and Aspergillus fumigatus using the broth microdilution method. Cytotoxicity was assessed using an MTT assay on human embryonic kidney cells HEK293 and human skin fibroblast cells hFB-hTERT6, as well as a hemolysis assay on erythrocytes. Membrane activity was analyzed by fluorimetric measurement of calcein leakage from model liposomes. Results: Derivatives containing the N-(hydroxyethyl)amino)ethyl fragment (compounds 3 and 4) exhibited relatively high antifungal activity, as did N-(2-hydroxyethyl)amides 5 and 9. Bis-modified compounds 6 and 10 did not outperform their mono-modified analogues in terms of activity or cytotoxicity. The mono-N-alkylated compound 3 showed the highest activity/toxicity ratio, which correlated well with its selectivity for ergosterol-containing model membranes. Discussion: Combining two successful modifications does not necessarily improve the activity/toxicity ratio of polyenes. Further studies can be performed for the optimization of carboxyl group of 3.

There is ample evidence showing the development of nystatin-resistant strains in patients undergoing malignancy treatment. Amphotericin B is a polyene antifungal drug that combines with ergosterol to cause cell death and is more effective on fungal species than routine antifungals such as nystatin. This study aimed to compare the effect of nystatin and amphotericin B on fungal species isolated from patients before and during head-and-neck radiotherapy. This in vitro experimental study was performed on samples isolated from patients undergoing head-and-neck radiotherapy before and during radiotherapy at Sayed al-Shohada Hospital in Isfahan, Iran. The isolates were identified by polymerase chain reaction-restriction fragment length polymorphism. Antifungal effects were determined by the microdilution method based on clinical and laboratory standards institute standards and minimum inhibitory concentration (MIC), minimum lethal concentration (MFC), drug sensitivity, and resistance were measured. The data were analyzed by SPSS version 22 (level of significance: 0.05). Before radiotherapy, all albicans strains were sensitive to nystatin, whereas 71.4% were sensitive to amphotericin B. After radiotherapy, Candida albicans strains were 100% sensitive to nystatin and 75% sensitive to amphotericin B. The present study showed that before radiotherapy, all species isolated from patients, including C. albicans, C. tropicalis, and C. glabrata, were sensitive to nystatin, whereas a percentage of albicans species showed resistance to amphotericin B. In the 2nd week of radiotherapy, the same as before radiotherapy, all species isolated from patients were sensitive to nystatin, whereas a percentage of albicans species showed resistance to amphotericin B. In general, the current study showed that before and after radiotherapy, the antifungal effect of nystatin is greater than amphotericin B.

Multidrug-resistant fungal pathogens and antifungal drug toxicity have challenged our current ability to fight fungal infections. Therefore, there is a strong global demand for novel antifungal molecules with the distinct mode of action and specificity to service the medical and agricultural sectors. Polyenes are a class of antifungal drugs with the broadest spectrum of activity among the current antifungal drugs. Epipyrone A, a water-soluble antifungal molecule with a unique, linear polyene structure, was isolated from the fungus Epiccocum nigrum. Since small changes in a compound structure can significantly alter its cell target and mode of action, we present here a study on the antifungal mode of action of the disalt of epipyrone A (DEA) using chemical-genetic profiling, fluorescence microscopy, and metabolomics. Our results suggest the disruption of sphingolipid/fatty acid biosynthesis to be the primary mode of action of DEA, followed by the intracellular accumulation of toxic phenolic compounds, in particular p-toluic acid (4-methylbenzoic acid). Although membrane ergosterol is known to be the main cell target for polyene antifungal drugs, we found little evidence to support that is the case for DEA. Sphingolipids, on the other hand, are known for their important roles in fungal cell physiology, and their biosynthesis has been recognized as a potential fungal-specific cell target for the development of new antifungal drugs.

Biofertilizers are environmentally friendly compounds that can enhance plant growth and substitute for chemically synthesized products. In this research, a new strain of the bacterium Bacillus velezensis, designated JZ, was isolated from the roots of strawberry plants and exhibited potent antagonistic properties against Bacillus altitudinis m-1, a pathogen responsible for leaf spot disease in strawberry. The fermentation broth of JZ exerted an inhibition rate of 47.43% against this pathogen. Using an optimized acid precipitation method, crude extracts of lipopeptides from the JZ fermentation broth were obtained. The crude extract of B. velezensis JZ fermentation broth did not significantly disrupt the cell permeability of B. altitudinis m-1, whereas it notably reduced the Ca2+-ATPase activity on the cell membrane and markedly elevated the intracellular reactive oxygen species (ROS) concentration. To identify the active compounds within the crude extract, QTOF-MS/MS was employed, revealing four antimicrobial compounds: fengycin, iturin, surfactin, and a polyene antibiotic known as bacillaene. The strain JZ also produced various plant-growth-promoting substances, such as protease, IAA, and siderophore, which assists plants to survive under pathogen infection. These findings suggest that the JZ strain holds significant potential as a biological control agent against B. altitudinis, providing a promising avenue for the management of plant bacterial disease.

Polyene antibiotics have been used in antifungal therapy since the mid-twentieth century. They are highly valued for their broad spectrum of activity and the rarity of pathogen resistance to their action. However, their use in the treatment of systemic mycoses often results in serious side-effects. Recently, there has been a renewed interest in the development of new antifungal drugs based on polyenes, particularly due to the emergence of highly dangerous pathogenic strains of fungi, such as Candida auris, and the increased incidence of mucormycosis. Considerable understanding has been established regarding the structure-biological activity relationships of polyene antifungals. Yet, no previous studies have examined the effect of introducing quaternized fragments into their molecular structure. In this study, we present a series of amides of amphotericin B, nystatin, and natamycin bearing a quaternized group in the side chain, and discuss their biological properties: antifungal activity, cytotoxicity, and effects on lipid bilayers that mimic fungal and mammalian cell membranes. Our research findings suggest that the nature of the introduced quaternized residue plays a more significant role than merely the introduction of a constant positive charge. Among the tested polyenes, derivatives 4b, 5b, and 6b, which contain a fragment of N-methyl-4-(aminomethyl)pyridinium in their structure, are particularly noteworthy due to their biological activity.

Topical antifungals with activity against dermatophytes include amorolfine, allylamines, azoles, ciclopiroxolamine, and tolnaftate. Polyene antimycotics, such as amphotericinB and nystatin, alternatively, miconazole are suitable for yeast infections of the skin and mucous membranes. For severe yeast infections of the skin and mucous membranes, oral triazole antimycotics, such as fluconazole and itraconazole, are used. Pityriasis versicolor is treated topically with antimycotics, and in severe forms also orally with itraconazole, alternatively fluconazole. Terbinafine, itraconazole and fluconazole are currently available for the systemic treatment of severe dermatophytoses, tinea capitis and onychomycosis. In addition to proven therapeutic regimens, unapproved (off-label use) intermittent low-dose therapies are increasingly being used, particularly in onychomycosis. Oral antimycotics for the treatment of tinea capitis and onychomycosis in children and adolescents can only be used off-label in Germany. In general, any oral antifungal treatment should always be combined with topical antifungal therapy. In tinea corporis and tinea cruris caused by Trichophyton (T.) mentagrophytes ITS (internal transcribed spacer) genotype VIII (T.indotineae), there is usually terbinafine resistance. Identification of the species and genotype of the dermatophyte and resistance testing are required. The drug of choice for T.mentagrophytes ITS genotype VIII dermatophytoses is itraconazole. In individual cases, treatment-refractory onychomycosis may be due to terbinafine resistance of T.rubrum. Here too, resistance testing and alternative treatment with itraconazole should be considered. Therapy monitoring should be carried out culturally and, if possible, using molecular methods (polymerase chain reaction). Alternative treatment options include laser application, and photodynamic therapy (PDT).

The threat of antibiotic resistance of fungal pathogens and the high toxicity of the most effective drugs, polyene macrolides, force us to look for new ways to develop innovative antifungal formulations. The aim of this study was to determine how the sterol, phospholipid, and flavonoid composition of liposomal forms of polyene antibiotics, and in particular, amphotericin B (AmB), affects their ability to increase the permeability of lipid bilayers that mimic the membranes of mammalian and fungal cells. To monitor the membrane permeability induced by various polyene-based lipid formulations, a calcein leakage assay and the electrophysiological technique based on planar lipid bilayers were used. The replacement of cholesterol with its biosynthetic precursor, 7-dehydrocholesterol, led to a decrease in the ability of AmB-loaded liposomes to permeabilize lipid bilayers mimicking mammalian cell membranes. The inclusion of plant flavonoid phloretin in AmB-loaded liposomes increased the ability of the formulation to disengage a fluorescent marker from lipid vesicles mimicking the membranes of target fungi. I-V characteristics of the fungal-like lipid bilayers treated with the AmB phytosomes were symmetric, demonstrating the functioning of double-length AmB pores and assuming a decrease in the antibiotic threshold concentration. The therapeutic window of polyene lipid formulations might be expanded by varying their sterol composition. Polyene-loaded phytosomes might be considered as the prototypes for innovative lipid antibiotic formulations.

The aim of the work was to analyse biosynthetic gene clusters (BGC) of Bacillus velezensis ONU 553 based on bioinformatics approach. Methods. Identification of species was processed with tools of TYGS server; EzBioCloud was used to calculate ANI. Analysis of biosynthetic gene, bacteriocin, and antibiotic resistance gene clusters using antiSMASH, Bagel4, respectively. The results. It is shown that the results of identification, phylogenetic analysis and DNA-DNA hybridization (DDH) carried out in silico proved that the strain Bacillus velezensis ONU 553 belongs to the operational group B. amyloliquefaciens (OGBa). Sequences identified as possible phages and CpG-islands were found in the genome of our strain. 12 biosynthetic gene clusters (BGC) were identified using antiSMASH. One new cluster capable of synthesizing a new metabolite was identified (region 11). The presence of two clusters of bacteriocins in the genome of Bacillus velezensis ONU 553, which are assigned to uberolysin/carnocyclin and the antimicrobial peptide LCI based on the identification of the core gene, is shown. Conclusions. The preliminary identification of the Bacillus velezensis ONU 553 strain as a representative of the Bacillus velezensis strain of the B. amyloliquefaciens group (OGBa) was confirmed. The presence of gene clusters of secondary metabolites responsible for the synthesis of surfactins, polyene antibiotics, antimicrobial peptides, macrolide antibiotics and bacteriocins was shown. The obtained results indicate that the Bacillus velezensis ONU 553 strain is promising for use in the field of "Blue Biotechnology" for the development of new drugs with antimicrobial and antifungal activity.