Galleria mellonella: The Versatile Host for Drug Discovery, In Vivo Toxicity Testing and Characterising Host-Pathogen Interactions

Exploring the potential of isorhapontigenin: attenuating Staphylococcus aureus virulence through MgrA-mediated regulation

The emerging prevalence of drug-resistant Staphylococcus aureus isolates underscores the urgent need for alternative therapeutic strategies due to the declining effectiveness of traditional antibiotics in clinical settings. MgrA, a key virulence regulator in S. aureus, orchestrates the expression of numerous virulence factors. Here, we report the discovery of isorhapontigenin, a methoxylated analog of resveratrol, as a potential anti-virulence agent against S. aureus. Isorhapontigenin effectively inhibits the hemolytic activity of S. aureus in a non-bactericidal manner. Additionally, it significantly reduces the cytotoxicity of S. aureus and impairs its ability to survive in macrophages. Mechanistically, isorhapontigenin modulates the expression of virulence factors, dose-dependently downregulating hla and upregulating the MgrA-regulated gene spa. Electrophoretic mobility shift assays demonstrated that isorhapontigenin inhibits the binding of MgrA to the hla promoter in a dose-dependent manner. Thermal shift assays confirmed the direct interaction between isorhapontigenin and the MgrA protein. The in vivo experiments demonstrated that isorhapontigenin significantly reduced the area of skin abscesses and improved survival in a pneumonia model while decreasing bacterial burden and inflammation in the lungs. In conclusion, isorhapontigenin holds potential as a candidate drug for further development as an anti-virulence agent for treating S. aureus infections.

IMPORTANCE

The emergence of antibiotic-resistant Staphylococcus aureus strains presents a formidable challenge to public health, necessitating novel approaches in combating these pathogens. Traditional antibiotics are becoming increasingly ineffective, leading to a pressing need for innovative therapeutic strategies. In this study, targeting virulence factors that play a crucial role in the pathogenesis of bacterial infections offers a promising alternative to circumvent resistance mechanisms. The discovery of isorhapontigenin as an inhibitor of S. aureus virulence represents a significant advance in anti-virulence therapy.

Synthesis of Novel Triazine-Based Chalcones and 8,9-dihydro-7H-pyrimido[4,5-b][1,4]diazepines as Potential Leads in the Search of Anticancer, Antibacterial and Antifungal Agents

This study presents the synthesis of four series of novel hybrid chalcones (20,21)a-g and (23,24)a-g and six series of 1,3,5-triazine-based pyrimido[4,5-b][1,4]diazepines (28-33)a-g and the evaluation of their anticancer, antibacterial, antifungal, and cytotoxic properties. Chalcones 20b,d, 21a,b,d, 23a,d-g, 24a-g and the pyrimido[4,5-b][1,4]diazepines 29e,g, 30g, 31a,b,e-g, 33a,b,e-g exhibited outstanding anticancer activity against a panel of 60 cancer cell lines with GI50 values between 0.01 and 100 μM and LC50 values in the range of 4.09 μM to >100 μM, several of such derivatives showing higher activity than the standard drug 5-fluorouracil (5-FU). On the other hand, among the synthesized compounds, the best antibacterial properties against N. gonorrhoeae, S. aureus (ATCC 43300), and M. tuberculosis were exhibited by the pyrimido[4,5-b][1,4]diazepines (MICs: 0.25-62.5 µg/mL). The antifungal activity studies showed that triazinylamino-chalcone 29e and triazinyloxy-chalcone 31g were the most active compounds against T. rubrum and T. mentagrophytes and A. fumigatus, respectively (MICs = 62.5 μg/mL). Hemolytic activity studies and in silico toxicity analysis demonstrated that most of the compounds are safe.

Structure-Activity Relationship Study to Develop Peptide Amphiphiles as Species-Specific Antimicrobials

Antimicrobial peptide amphiphiles (PAs) are a promising class of molecules that can disrupt the bacterial membrane or act as drug nanocarriers. In this study, we prepared 33 PAs to establish supramolecular structure-activity relationships. We studied the morphology and activity of the nanostructures against different Gram-positive and Gram-negative bacterial strains (such as Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii). Next, we used principal component analysis (PCA) to determine the key contributors to activity. We found that for S. aureus, the zeta potential was the major contributor to the activity while Gram-negative bacteria were more influenced by the partition coefficient (LogP) with the following order P. aeruginosa>E. coli>A. baumannii. We also performed a study of the mechanism of action of selected PAs on the bacterial membrane assessing the membrane permeability and depolarization, changes in zeta potential and overall integrity. We studied the toxicity of the nanostructures against mammalian cells. Finally, we performed an in vivo study using the wax moth larvae to determine the therapeutic efficacy of the active PAs. This study shows cationic PA nanostructures can be an intriguing platform for the development of nanoantibacterials.

MptpB Inhibitor Improves the Action of Antibiotics against Mycobacterium tuberculosis and Nontuberculous Mycobacterium avium Infections

Treatment of Mycobacterium tuberculosis and Mycobacterium avium infections requires multiple drugs for long time periods. Mycobacterium protein-tyrosine-phosphatase B (MptpB) is a key M. tuberculosis virulence factor that subverts host antimicrobial activity to promote intracellular survival. Inhibition of MptpB reduces the infection burden in vivo and offers new opportunities to improve current treatments. Here, we demonstrate that M. avium produces an MptpB orthologue and that the MptpB inhibitor C13 reduces the M. avium infection burden in macrophages. Combining C13 with the antibiotics rifampicin or bedaquiline showed an additive effect, reducing intracellular infection of both M. tuberculosis and M. avium by 50%, compared to monotreatment with antibiotics alone. This additive effect was not observed with pretomanid. Combining C13 with the minor groove-binding compounds S-MGB-362 and S-MGB-363 also reduced the M. tuberculosis intracellular burden. Similar additive effects of C13 and antibiotics were confirmed in vivo using Galleria mellonella infections. We demonstrate that the reduced mycobacterial burden in macrophages observed with C13 treatments is due to the increased trafficking to lysosomes.

In silico prediction and in vitro assessment of novel heterocyclics with antimalarial activity

The development of new antimalarials is paramount to keep the goals on reduction of malaria cases in endemic regions. The search for quality hits has been challenging as many inhibitory molecules may not progress to the next development stage. The aim of this work was to screen an in-house library of heterocyclic compounds (HCUV) for antimalarial activity combining computational predictions and phenotypic techniques to find quality hits. The physicochemical determinants, pharmacokinetic properties (ADME), and drug-likeness of HCUV were evaluated in silico, and compounds were selected for structure-based virtual screening and in vitro analysis. Seven Plasmodium target proteins were selected from the DrugBank Database, and ligands and receptors were processed using UCSF Chimera and Open Babel before being subjected to docking using Autodock Vina and Autodock 4. Growth inhibition of P. falciparum (3D7) cultures was tested by SYBR Green assays, and toxicity was assessed using hemolytic activity tests and the Galleria mellonella in vivo model. From a total of 792 compounds, 341 with good ADME properties, drug-likeness, and no interference structures were subjected to in vitro analysis. Eight compounds showed IC50 ranging from 0.175 to 0.990 µM, and active compounds included pyridyl-diaminopyrimido-diazepines, pyridyl-N-acetyl- and pyridyl-N-phenyl-pyrazoline derivatives. The most potent compound (UV802, IC50 0.178 µM) showed no toxicophoric and was predicted to interact with P. falciparum 1-cysperoxidredoxin (PfPrx1). For the remaining 7 hits (IC50 < 1 μM), 3 showed in silico binding to PfPrx1, one was predicted to bind the haloacid dehalogenase-like hydrolase and plasmepsin II, and one interacted with the plasmodial heat shock protein 90.

Pathogenetic characterization of a Micrococcus luteus strain isolated from an infant

Purpose

To explore the clinical characteristics of Micrococcus luteus bloodstream infection in an infant and characterize the phenotype and genotype of the isolated strains, as well as seek suitable infection models for assessing virulence.

Methods

Clinical data was collected from an infant patient diagnosed with M. luteus bloodstream infection. Metagenomic sequencing was performed on the isolated blood sample. The strain was isolated and underwent mass spectrometry, biochemical tests, antibiotic susceptibility assays, and whole-genome sequencing. The Galleria mellonella infection model was used to assess M. luteus virulence.

Results

Patient responded poorly to cephalosporins, but recovered after Linezolid treatment. Metagenomic sequencing identified M. luteus as the predominant species in the sample, confirming infection. They were identified as M. luteus with a high confidence level of 98.99% using mass spectrometry. The strain showed positive results for Catalase, Oxidase, and Urea tests, and negative results for Mannose, Xylose, Lactose, Mannitol, Arginine, and Galactose tests, consistent with the biochemical profile of M. luteus reference standards. M. luteus susceptibility to 15 antibiotics was demonstrated and no resistance genes were detected. Predicted virulence genes, including clpB, were associated with metabolic pathways and the type VI secretion system. The infection model demonstrated dose-dependent survival rates.

Conclusion

The infant likely developed a bloodstream infection with M. luteus due to compromised immunity. Although the isolated strain is sensitive to cephalosporin antibiotics and has low pathogenicity in infection models, clinical treatment with cephalosporins was ineffective. Linezolid proved to be effective, providing valuable guidance for future clinical management of such rare infections.

Our current clinical understanding of Candida biofilms: where are we two decades on?

Clinically we have been aware of the concept of Candida biofilms for many decades, though perhaps without the formal designation. Just over 20 years ago the subject emerged on the back of progress made from the bacterial biofilms, and academic progress pace has continued to mirror the bacterial biofilm community, albeit at a decreased volume. It is apparent that Candida species have a considerable capacity to colonize surfaces and interfaces and form tenacious biofilm structures, either alone or in mixed species communities. From the oral cavity, to the respiratory and genitourinary tracts, wounds, or in and around a plethora of biomedical devices, the scope of these infections is vast. These are highly tolerant to antifungal therapies that has a measurable impact on clinical management. This review aims to provide a comprehensive overight of our current clinical understanding of where these biofilms cause infections, and we discuss existing and emerging antifungal therapies and strategies.

Dechlorination of wastewater from shell-based glucosamine processing by mangrove wetland-derived fungi

Wastewater from processing crustacean shell features ultrahigh chloride content. Bioremediation of the wastewater is challenging due to the high chloride ion content, making it inhospitable for most microorganisms to survive and growth. In this study, mangrove wetland-derived fungi were first tested for their salt tolerance, and the highly tolerant isolates were cultured in shrimp processing wastewater and the chloride concentration was monitored. Notably, the filamentous fungal species Aspergillus piperis could remove over 70% of the chloride in the wastewater within 3 days, with the fastest biomass increase (2.01 times heavier) and chloride removal occurring between day one and two. The chloride ions were sequestered into the fungal cells. The genome of this fungal species contained Cl- conversion enzymes, which may have contributed to the ion removal. The fungal strain was found to be of low virulence in larval models and could serve as a starting point for further considerations in bioremediation of shell processing wastewater, promoting the development of green technology in the shell processing industry.

Alternatives to animal models to study bacterial infections

Animal testing has made a significant and unequalled contribution to important discoveries and advancements in the fields of research, medicine, vaccine development, and drug discovery. Each year, millions of animals are sacrificed for various experiments, and this is an ongoing process. However, the debate on the ethical and sensible usage of animals in in vivo experimentation is equally important. The need to explore and adopt newer alternatives to animals so as to comply with the goal of reduce, refine, and replace needs attention. Besides the ever-increasing debate on ethical issues, animal research has additional drawbacks (need of trained labour, requirement of breeding area, lengthy protocols, high expenses, transport barriers, difficulty to extrapolate data from animals to humans, etc.). With this scenario, the present review has been framed to give a comprehensive insight into the possible alternative options worth exploring in this direction especially targeting replacements for animal models of bacterial infections. There have been some excellent reviews discussing on the alternate methods for replacing and reducing animals in drug research. However, reviews that discuss the replacements in the field of medical bacteriology with emphasis on animal bacterial infection models are purely limited. The present review discusses on the use of (a) non-mammalian models and (b) alternative systems such as microfluidic chip-based models and microdosing aiming to give a detailed insight into the prospects of these alternative platforms to reduce the number of animals being used in infection studies. This would enlighten the scientific community working in this direction to be well acquainted with the available new approaches and alternatives so that the 3R strategy can be successfully implemented in the field of antibacterial drug research and testing.

Synthesis and Anti-Mycobacterium tuberculosis Activity of Imidazo[2,1-b][1,3]oxazine Derivatives against Multidrug-Resistant Strains

The emergence of multidrug-resistant strains of M. tuberculosis has raised concerns due to the greater difficulties in patient treatment and higher mortality rates. Herein, we revisited the 2-nitro-6,7-dihydro-5H-imidazo[2,1-b][1,3]oxazine scaffold and identified potent new carbamate derivatives having MIC90 values of 0.18-1.63 μM against Mtb H37Rv. Compounds 47-49, 51-53, and 55 exhibited remarkable activity against a panel of clinical isolates, displaying MIC90 values below 0.5 μM. In Mtb-infected macrophages, several compounds demonstrated a 1-log greater reduction in mycobacterial burden than rifampicin and pretomanid. The compounds tested did not exhibit significant cytotoxicity against three cell lines or any toxicity to Galleria mellonella. Furthermore, the imidazo[2,1-b][1,3]oxazine derivatives did not show substantial activity against other bacteria or fungi. Finally, molecular docking studies revealed that the new compounds could interact with the deazaflavin-dependent nitroreductase (Ddn) in a similar manner to pretomanid. Collectively, our findings highlight the chemical universe of imidazo[2,1-b][1,3]oxazines and their promising potential against MDR-TB.

Using SMART Magnetic Fluids and Gels for Prevention and Destruction of Bacterial Biofilms

Biofouling is a major problem in all natural and artificial settings where solid surfaces meet liquids in the presence of living microorganisms. Microbes attach to the surface and form a multidimensional slime that protects them from unfavorable environments. These structures, known as biofilms, are detrimental and very hard to remove. Here, we used SMART magnetic fluids [ferrofluids (FFs), magnetorheological fluids (MRFs), and ferrogels (FGs) containing iron oxide nano/microparticles] and magnetic fields to remove bacterial biofilms from culture tubes, glass slides, multiwell plates, flow cells, and catheters. We compared the ability of different SMART fluids to remove biofilms and found that commercially available, as well as homemade, FFs, MRFs, and FGs can successfully remove biofilm more efficiently than traditional mechanical methods, especially from textured surfaces. In tested conditions, SMARTFs reduced bacterial biofilms by five orders of magnitude. The ability to remove biofilm increased with the amount of magnetic particles; therefore, MRFs, FG, and homemade FFs with high amounts of iron oxide were the most efficient. We showed also that SMART fluid deposition can protect a surface from bacterial attachment and biofilm formation. Possible applications of these technologies are discussed.

Galleria mellonella-A Model for the Study of aPDT-Prospects and Drawbacks

Galleria mellonella is a promising in vivo model insect used for microbiological, medical, and pharmacological research. It provides a platform for testing the biocompatibility of various compounds and the kinetics of survival after an infection followed by subsequent treatment, and for the evaluation of various parameters during treatment, including the host-pathogen interaction. There are some similarities in the development of pathologies with mammals. However, a limitation is the lack of adaptive immune response. Antimicrobial photodynamic therapy (aPDT) is an alternative approach for combating microbial infections, including biofilm-associated ones. aPDT is effective against Gram-positive and Gram-negative bacteria, viruses, fungi, and parasites, regardless of whether they are resistant to conventional treatment. The main idea of this comprehensive review was to collect information on the use of G. mellonella in aPDT. It provides a collection of references published in the last 10 years from this area of research, complemented by some practical experiences of the authors of this review. Additionally, the review summarizes in brief information on the G. mellonella model, its advantages and methods used in the processing of material from these larvae, as well as basic knowledge of the principles of aPDT.

In Vitro and In Vivo Biocompatibility of Natural and Synthetic Pseudomonas aeruginosa Pyomelanin for Potential Biomedical Applications

Bacteria are the source of many bioactive compounds, including polymers with various physiological functions and the potential for medical applications. Pyomelanin from Pseudomonas aeruginosa, a nonfermenting Gram-negative bacterium, is a black-brown negatively charged extracellular polymer of homogentisic acid produced during L-tyrosine catabolism. Due to its chemical properties and the presence of active functional groups, pyomelanin is a candidate for the development of new antioxidant, antimicrobial and immunomodulatory formulations. This work aimed to obtain bacterial water-soluble (Pyo_sol), water-insoluble (Pyo_insol) and synthetic (sPyo) pyomelanin variants and characterize their chemical structure, thermosensitivity and biosafety in vitro and in vivo (Galleria mallonella). FTIR analysis showed that aromatic ring connections in the polymer chains were dominant in Pyo_sol and sPyo, whereas Pyo_insol had fewer C_ar-C_ar links between rings. The differences in chemical structure influence the solubility of various forms of pyomelanins, their thermal stability and biological activity. Pyo_sol and Pyo_insol showed higher biological safety than sPyo. The obtained results qualify Pyo_sol and Pyo_insol for evaluation of their antimicrobial, immunomodulatory and proregenerative activities.

Anti-Biofilm Activity of Phenyllactic Acid against Clinical Isolates of Fluconazole-Resistant Candida albicans

Commonly found colonizing the human microbiota, Candida albicans is a microorganism known for its ability to cause infections, mainly in the vulvovaginal region, and is responsible for 85% to 90% of vulvovaginal candidiasis (VVC) cases. The development of drug resistance in C. albicans isolates after long-term therapy with fluconazole is an important complication to solve and new therapeutic strategies are required to target this organism and its pathogenicity. In the present study, phenyllactic acid (PLA) an important broad-spectrum antimicrobial compound was investigated for its antifungal and antivirulence activities against clinical isolates of C. albicans. Previously characterized strains of C. albicans isolates from women with VVC and C. albicans ATCC90028 were used to evaluate the antimicrobial and time dependent killing assay activity of PLA showing a MIC 7.5 mg mL−1 and a complete reduction of viable Candida cells detected by killing kinetics after 4 h of treatment with PLA. Additionally, PLA significantly reduced the biomass and the metabolic activity of C. albicans biofilms and impaired biofilm formation also with changes in ERG11, ALS3, and HWP1 genes expression as detected by qPCR. PLA eradicated pre-formed biofilms as showed also with confocal laser scanning microscopy (CLSM) observations. Furthermore, the compound prolonged the survival rate of Galleria mellonella infected by C. albicans isolates. These results indicate that PLA is a promising candidate as novel and safe antifungal agents for the treatment of vulvovaginal candidiasis.

The Virtuous Galleria mellonella Model for Scientific Experimentation

The first research on the insect Galleria mellonella was published 85 years ago, and the larva is now widely used as a model to study infections caused by bacterial and fungal pathogens, for screening new antimicrobials, to study the adjacent immune response in co-infections or in host-pathogen interaction, as well as in a toxicity model. The immune system of the G. mellonella model shows remarkable similarities with mammals. Furthermore, results from G. mellonella correlate positively with mammalian models and with other invertebrate models. Unlike other invertebrate models, G. mellonella can withstand temperatures of 37 °C, and its handling and experimental procedures are simpler. Despite having some disadvantages, G. mellonella is a virtuous in vivo model to be used in preclinical studies, as an intermediate model between in vitro and mammalian in vivo studies, and is a great example on how to apply the bioethics principle of the 3Rs (Replacement, Reduction, and Refinement) in animal experimentation. This review aims to discuss the progress of the G. mellonella model, highlighting the key aspects of its use, including experimental design considerations and the necessity to standardize them. A different score in the “cocoon” category included in the G. mellonella Health Index Scoring System is also proposed.

Insects and Public Health: An Overview

Insects are, by far, the most common animals on our planet. The ubiquity and plethora of ecological niches occupied by insects, along with the strict and sometimes forced coexistence between insects and humans, make insects a target of public health interest. This article reports the negative aspects historically linked to insects as pests and vectors of diseases, and describes their potential as bioindicators of environmental pollution, and their use as food and feed. Both negative and positive impacts of insects on human and animal health need to be addressed by public health professionals who should aim to strike a balance within the wide range of sometimes conflicting goals in insect management, such as regulating their production, exploiting their potential, protecting their health and limiting their negative impact on animals and humans. This requires increased insect knowledge and strategies to preserve human health and welfare. The aim of this paper is to provide an overview of traditional and emerging topics bridging insects and public health to highlight the need for professionals, to address these topics during their work. The present and future role and activities of public health authorities regarding insects are analyzed.

Clearing an ESKAPE Pathogen in a Model Organism; A Polypyridyl Ruthenium(II) Complex Theranostic that Treats a Resistant Acinetobacter baumannii Infection in Galleria mellonella

In previous studies we have described the therapeutic action of luminescent dinuclear ruthenium(II) complexes based on the tetrapyridylphenazine, tpphz, bridging ligand on pathogenic strains of Escherichia coli and Enterococcus faecalis. Herein, the antimicrobial activity of the complex against pernicious Gram-negative ESKAPE pathogenic strains of Acinetobacter baumannii (AB12, AB16, AB184 and AB210) and Pseudomonas aeruginosa (PA2017, PA_ 007_ IMP and PA_ 004_ CRCN) are reported. Estimated minimum inhibitory concentrations and minimum bactericidal concentrations for the complexes revealed the complex shows potent activity against all A. baumannii strains, in both glucose defined minimal media and standard nutrient rich Mueller-Hinton-II. Although the activity was lower in P. aureginosa, a moderately high potency was observed and retained in carbapenem-resistant strains. Optical microscopy showed that the compound is rapidly internalized by A. baumannii. As previous reports had revealed the complex exhibited no toxicity in Galleria Mellonella up to concentrations of 80 mg/kg, the ability to clear pathogenic infection within this model was explored. The pathogenic concentrations to the larvae for each bacterium were determined to be≥105 for AB184 and≥103 CFU/mL for PA2017. It was found a single dose of the compound totally cleared a pathogenic A. baumannii infection from all treated G. mellonella within 96 h. Uniquely, in these conditions thanks to the imaging properties of the complex the clearance of the bacteria within the hemolymph of G. mellonella could be directly visualized through both optical and transmission electron microscopy.

Preliminary Toxicity Evaluation of a Porphyrin Photosensitizer in an Alternative Preclinical Model

In photodynamic therapy (PDT), a photosensitizer (PS) excited with a specific wavelength, and in the presence of oxygen, gives rise to photochemical reactions that lead to cell damage. Over the past few years, larval stages of the G. mellonella moth have proven to be an excellent alternative animal model for in vivo toxicity testing of novel compounds and virulence testing. In this article, we report a series of preliminary studies on G. mellonella larvae to evaluate the photoinduced stress response by a porphyrin (PS) (TPPOH). The tests performed evaluated PS toxicity on larvae and cytotoxicity on hemocytes, both in dark conditions and following PDT. Cellular uptake was also evaluated by fluorescence and flow cytometry. The results obtained demonstrate how the administration of PS and subsequent irradiation of larvae affects not only larvae survival rate, but also immune system cells. It was also possible to verify PS's uptake and uptake kinetics in hemocytes, observing a maximum peak at 8 h. Given the results obtained in these preliminary tests, G. mellonella appears to be a promising model for preclinical PS tests.

Diversity, Dynamics and Therapeutic Application of Clostridioides difficile Bacteriophages

Clostridioides difficile causes antibiotic-induced diarrhoea and pseudomembranous colitis in humans and animals. Current conventional treatment relies solely on antibiotics, but C. difficile infection (CDI) cases remain persistently high with concomitant increased recurrence often due to the emergence of antibiotic-resistant strains. Antibiotics used in treatment also induce gut microbial imbalance; therefore, novel therapeutics with improved target specificity are being investigated. Bacteriophages (phages) kill bacteria with precision, hence are alternative therapeutics for the targeted eradication of the pathogen. Here, we review current progress in C. difficile phage research. We discuss tested strategies of isolating C. difficile phages directly, and via enrichment methods from various sample types and through antibiotic induction to mediate prophage release. We also summarise phenotypic phage data that reveal their morphological, genetic diversity, and various ways they impact their host physiology and pathogenicity during infection and lysogeny. Furthermore, we describe the therapeutic development of phages through efficacy testing in different in vitro, ex vivo and in vivo infection models. We also discuss genetic modification of phages to prevent horizontal gene transfer and improve lysis efficacy and formulation to enhance stability and delivery of the phages. The goal of this review is to provide a more in-depth understanding of C. difficile phages and theoretical and practical knowledge on pre-clinical, therapeutic evaluation of the safety and effectiveness of phage therapy for CDI.

Lycopene, Mesoporous Silica Nanoparticles and Their Association: A Possible Alternative against Vulvovaginal Candidiasis?

Commonly found colonizing the human microbiota, Candida albicans is a microorganism known for its ability to cause infections, mainly in the vulvovaginal region known as vulvovaginal candidiasis (VVC). This pathology is, in fact, one of the main C. albicans clinical manifestations, changing from a colonizer to a pathogen. The increase in VVC cases and limited antifungal therapy make C. albicans an increasingly frequent risk in women's lives, especially in immunocompromised patients, pregnant women and the elderly. Therefore, it is necessary to develop new therapeutic options, especially those involving natural products associated with nanotechnology, such as lycopene and mesoporous silica nanoparticles. From this perspective, this study sought to assess whether lycopene, mesoporous silica nanoparticles and their combination would be an attractive product for the treatment of this serious disease through microbiological in vitro tests and acute toxicity tests in an alternative in vivo model of Galleria mellonella. Although they did not show desirable antifungal activity for VVC therapy, the present study strongly encourages the use of mesoporous silica nanoparticles impregnated with lycopene for the treatment of other human pathologies, since the products evaluated here did not show toxicity in the in vivo test performed, being therefore, a topic to be further explored.

Azole-Based Compounds That Are Active against Candida Biofilm: In Vitro, In Vivo and In Silico Studies

Fungal pathogens, including Candida spp., Aspergillus spp. and dermatophytes, cause more than a billion human infections every year. A large library of imidazole- and triazole-based compounds were in vitro screened for their antifungal activity against C. albicans, C. glabrata, C. krusei, A. fumigatus and dermatophytes, such as Microsporum gypseum, Trichophyton rubrum and Trichophyton mentagrophytes. The imidazole carbamate 12 emerged as the most active compound, showing a valuable antifungal activity against C. glabrata (MIC 1−16 μg/mL) and C. krusei (MIC 4−24 μg/mL). No activity against A. fumigatus or the dermatophytes was observed among all the tested compounds. The compound 12 inhibited the formation of C. albicans, C. glabrata and C. krusei biofilms and reduced the mature Candida biofilm. In the Galleria mellonella larvae, 12 showed a significant reduction in the Candida infection, together with a lack of toxicity at the concentration used to activate its antifungal activity. Moreover, the in silico prediction of the putative targets revealed that the concurrent presence of the imidazole core, the carbamate and the p-chlorophenyl is important for providing a strong affinity for lanosterol 14α-demethylase (CgCYP51a1) and the fungal carbonic anhydrase (CgNce103), the S-enantiomer being more productive in these interactions.

Antimicrobial Efficacy of Green Synthesized Nanosilver with Entrapped Cinnamaldehyde against Multi-Drug-Resistant Enteroaggregative Escherichia coli in Galleria mellonella

The global emergence of antimicrobial resistance (AMR) needs no emphasis. In this study, the in vitro stability, safety, and antimicrobial efficacy of nanosilver-entrapped cinnamaldehyde (AgC) against multi-drug-resistant (MDR) strains of enteroaggregative Escherichia coli (EAEC) were investigated. Further, the in vivo antibacterial efficacy of AgC against MDR-EAEC was also assessed in Galleria mellonella larval model. In brief, UV-Vis and Fourier transform infrared (FTIR) spectroscopy confirmed effective entrapment of cinnamaldehyde with nanosilver, and the loading efficiency was estimated to be 29.50 ± 0.56%. The AgC was of crystalline form as determined by the X-ray diffractogram with a mono-dispersed spherical morphology of 9.243 ± 1.83 nm in electron microscopy. AgC exhibited a minimum inhibitory concentration (MIC) of 0.008−0.016 mg/mL and a minimum bactericidal concentration (MBC) of 0.008−0.032 mg/mL against MDR- EAEC strains. Furthermore, AgC was stable (high-end temperatures, proteases, cationic salts, pH, and host sera) and tested safe for sheep erythrocytes as well as secondary cell lines (RAW 264.7 and HEp-2) with no negative effects on the commensal gut lactobacilli. in vitro, time-kill assays revealed that MBC levels of AgC could eliminate MDR-EAEC infection in 120 min. In G. mellonella larvae, AgC (MBC values) increased survival, decreased MDR-EAEC counts (p < 0.001), had an enhanced immunomodulatory effect, and was tested safe to the host. These findings infer that entrapment enhanced the efficacy of cinnamaldehyde and AgNPs, overcoming their limitations when used individually, indicating AgC as a promising alternative antimicrobial candidate. However, further investigation in appropriate animal models is required to declare its application against MDR pathogens.

Galleria mellonella as a Novel In Vivo Model to Screen Natural Product-Derived Modulators of Innate Immunity

Immunomodulators are drugs that either stimulate or suppress the immune system in response to an immunopathological disease or cancer. The majority of clinically approved immunomodulators are either chemically synthesised (e.g., dexamethasone) or protein-based (e.g., monoclonal antibodies), whose uses are limited due to toxicity issues, poor bioavailability, or prohibitive cost. Nature is an excellent source of novel compounds, as it is estimated that almost half of all licenced medicines are derived from nature or inspired by natural product (NP) structures. The clinical success of the fungal-derived immunosuppressant cyclosporin A demonstrates the potential of natural products as immunomodulators. Conventionally, the screening of NP molecules for immunomodulation is performed in small animal models; however, there is a growing impetus to replace animal models with more ethical alternatives. One novel approach is the use of Galleria melonella larvae as an in vivo model of immunity. Despite lacking adaptive antigen-specific immunity, this insect possesses an innate immune system comparable to mammals. In this review, we will describe studies that have used this alternative in vivo model to assess the immunomodulating activity of synthetic and NP-derived compounds, outline the array of bioassays employed, and suggest strategies to enhance the use of this model in future research.

Potential Applications of Essential Oils for Environmental Sanitization and Antimicrobial Treatment of Intensive Livestock Infections

The extensive use of antibiotics has contributed to the current antibiotic resistance crisis. Livestock infections of Salmonella spp, Clostridium spp. and E. coli antimicrobial-resistant bacteria represent a public threat to human and animal health. To reduce the incidence of these zoonoses, essential oils (EOs) could be effective antibiotic alternatives. This study aims at identifying EOs safe for use, effective both in complementary therapy and in the environmental sanitization of intensive farming. Natural products were chemo-characterized by gas chromatography. Three S. Typhimurium, three C. perfringens and four E. coli strains isolated from poultry and swine farms were used to assess the antimicrobial properties of nine EOs and a modified GR-OLI (mGR-OLI). The toxicity of the most effective ones (Cinnamomum zeylanicum, Cz; Origanum vulgare, Ov) was also evaluated on porcine spermatozoa and Galleria mellonella larvae. Cz, Ov and mGR-OLI showed the strongest antimicrobial activity; their volatile components were also able to significantly inhibit the growth of tested strains. In vitro, Ov toxicity was slightly lower than Cz, while it showed no toxicity on G. mellonella larvae. In conclusion, the study confirms the importance of evaluating natural products to consolidate the idea of safe EO applications in reducing and preventing intensive livestock infections.