In Vitro Activity of Beauvericin against All Developmental Stages of Sarcoptes scabiei

ABC transporter inhibition by beauvericin partially overcomes drug resistance in Leishmania tropica

Leishmaniasis is a neglected tropical disease infecting the world's poorest populations. Miltefosine (ML) remains the primary oral drug against the cutaneous form of leishmaniasis. The ATP-binding cassette (ABC) transporters are key players in the xenobiotic efflux, and their inhibition could enhance the therapeutic index. In this study, the ability of beauvericin (BEA) to overcome ABC transporter-mediated resistance of Leishmania tropica to ML was assessed. In addition, the transcription profile of genes involved in resistance acquisition to ML was inspected. Finally, we explored the efflux mechanism of the drug and inhibitor. The efficacy of ML against all developmental stages of L. tropica in the presence or absence of BEA was evaluated using an absolute quantification assay. The expression of resistance genes was evaluated, comparing susceptible and resistant strains. Finally, the mechanisms governing the interaction between the ABC transporter and its ligands were elucidated using molecular docking and dynamic simulation. Relative quantification showed that the expression of the ABCG sub-family is mostly modulated by ML. In this study, we used BEA to impede resistance of Leishmania tropica. The IC50 values, following BEA treatment, were significantly reduced from 30.83, 48.17, and 16.83 µM using ML to 8.14, 11.1, and 7.18 µM when using a combinatorial treatment (ML + BEA) against promastigotes, axenic amastigotes, and intracellular amastigotes, respectively. We also demonstrated a favorable BEA-binding enthalpy to L. tropica ABC transporter compared to ML. Our study revealed that BEA partially reverses the resistance development of L. tropica to ML by blocking the alternate ATP hydrolysis cycle.

Rapid analysis of insecticidal metabolites from the entomopathogenic fungus Beauveria bassiana 331R using UPLC-Q-Orbitrap MS

Beauveria bassiana, a representative entomopathogenic fungus, is increasingly being utilized as an eco-friendly pest management alternative to chemical insecticides. This fungus produces a range of insecticidal secondary metabolites that act as antimicrobial and immunosuppressive agents. However, detailed qualitative and quantitative analysis related to these compounds remains scarce, we developed a method for the rapid analysis of these metabolites. Eight secondary metabolites (bassianin, bassianolide, beauvericin, beauveriolide I, enniatin A, A1, and B, and tenellin) were efficiently extracted when B. bassiana-infected Tenebrio molitor larvae were ground in 70% EtOH extraction solvent and subsequently subjected to ultrasonic treatment for 30 min. The eight metabolites were rapidly and simultaneously analyzed using ultra-performance liquid chromatography-quadrupole-Orbitrap mass spectrometry (UPLC-Q-Orbitrap MS). Bassianolide (20.6-51.1 µg/g) and beauvericin (63.6-109.8 µg/g) were identified as the main metabolites in B. basssiana-infected larvae, indicating that they are likely major toxins of B. bassiana. Validation of the method exhibited recovery rates in the range of 80-115% and precision in the range of 0.1-8.0%, indicating no significant interference from compounds in the matrix. We developed a method to rapidly analyze eight insecticidal metabolites using UPLC-Q-Orbitrap MS. This can be extensively utilized for detecting and producing insecticidal fungal secondary metabolites.

Three new metabolites from the endophyte Fusarium proliferatum T2-10

One new cyclopeptide, cyclo-(L-Trp-L-Phe-L-Phe) (1), one new 2-pyridone derivative, fusarone A (3), and one new natural indole derivative, ethyl 3-indoleacetate (4), along with six known compounds were isolated from the endophytic fungus Fusarium proliferatum T2-10. The planar structures of three new compounds were identified by spectral methods including 1D and 2D NMR techniques, and the absolute configuration of compound 1 was elucidated by Marfey-MS method. In addition, all compounds were evaluated for their cytotoxic and antibacterial activities in vitro. Compound 2 showed remarkable cytotoxic activities against two human hepatoma cell lines SMMC7721 and HepG2 with IC50 values of 5.89 ± 0.74 and 6.16 ± 0.52 μM, and showed moderate antibacterial activities against Staphylococcus aureus and Enterococcus faecalis with MIC values of 7.81 and 15.62 μg/mL, respectively.

Can Ivermectin kill Sarcoptes scabiei during the molting process?

BACKGROUND

Sarcoptes scabiei is a permanent obligate ectoparasite that lives and reproduces in the epidermis of humans and other mammals worldwide. There is a lack of information on the molting process of Sarcoptes scabiei. Ivermectin is widely used to treat Sarcoptes infection in humans and animals, while the survival of molting Sarcoptes mites in the presence of ivermectin is unknown. The aim of the present study is to investigate the molting process of Sarcoptes mites and assess the activity of ivermectin during the molting process of Sarcoptes mites.

METHODOLOGY/PRINCIPAL FINDINGS

molting Sarcoptes mites were incubated at 35°C and 80% relative humidity and observed hourly until complete molt. Of the 192 molting mites recorded, the longest molt periods for larvae and nymphs were 23 and 30 h, respectively. The activity of ivermectin on molting Sarcoptes mites was also assessed using two concentrations of the drug (0.1 and 0.05 mg/ml). The exposure time for molting mites was determined by 100% mortality of female mites exposed to the solution of ivermectin. While all female mites were killed after exposure to 0.1 mg/ml ivermectin for 2 h and and 0.05 mg/ml for 7 h, 32% and 36% of molting mites survived and successfully molted, respectively.

CONCLUSIONS/SIGNIFICANCE

The present study demonstrated that molting Sarcoptes mites are less susceptible to ivermectin than active mites. As a consequence, mites may survive after two doses of ivermectin given 7 days apart due not only to hatching eggs but also to the resistance of mites during their molting process. Our results provide insight into the optimal therapeutic regimens for scabies and highlight the need for further research on the molting process of Sarcoptes mites.

Pathogenesis and defense mechanism while Beauveria bassiana JEF-410 infects poultry red mite, Dermanyssus gallinae

The poultry red mite, Dermanyssus gallinae (Mesostigmata: Dermanyssidae), is a major pest that causes great damage to chicken egg production. In one of our previous studies, the management of red mites using entomopathogenic fungi was evaluated, and the acaricidal fungus Beauveria bassiana JEF-410 was selected for further research. In this study, we tried to elucidate the pathogenesis of B. bassiana JEF-410 and the defense mechanisms of red mites at a transcriptome level. Red mites collected from a chicken farm were treated with B. bassiana JEF-410. When the mortality of infected red mites reached 50%, transcriptome analyses were performed to determine the interaction between B. bassiana JEF-410 and red mites. Uninfected red mites and non-infecting fungus served as controls. In B. bassiana JEF-410, up-regulated gene expression was observed in tryptophan metabolism and secondary metabolite biosynthesis pathways. Genes related to acetyl-CoA synthesis were up-regulated in tryptophan metabolism, suggesting that energy metabolism and stress management were strongly activated. Secondary metabolites associated with fungal up-regulated DEGs were related to the production of substances toxic to insects such as beauvericin and beauveriolide, efflux pump of metabolites, energy production, and resistance to stress. In red mites, physical and immune responses that strengthen the cuticle against fungal infection were highly up-regulated. From these gene expression analyses, we identified essential factors for fungal infection and subsequent defenses of red mites. These results will serve as a strong platform for explaining the interaction between B. bassiana JEF-410 and red mites in the stage of active infection.

In silico evidence of beauvericin antiviral activity against SARS-CoV-2

Background

Scientists are still battling severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for the coronavirus 2019 (COVID-19) pandemic so human lives can be saved worldwide. Secondary fungal metabolites are of intense interest due to their broad range of pharmaceutical properties. Beauvericin (BEA) is a secondary metabolite produced by the fungus Beauveria bassiana. Although promising anti-viral activity has previously been reported for BEA, studies investigating its therapeutic potential are limited.

Methods

The objective of this study was to assess the potential usage of BEA as an anti-viral molecule via protein–protein docking approaches using MolSoft.

Results

In-silico results revealed relatively favorable binding energies for BEA to different viral proteins implicated in the vital life stages of this virus. Of particular interest is the capability of BEA to dock to both the main coronavirus protease (Pockets A and B) and spike proteins. These results were validated by molecular dynamic simulation (Gromacs). Several parameters, such as root-mean-square deviation/fluctuation, the radius of gyration, H-bonding, and free binding energy were analyzed. Computational analyses revealed that interaction of BEA with the main protease pockets in addition to the spike glycoprotein remained stable.

Conclusion

Altogether, our results suggest that BEA might be considered as a potential competitive and allosteric agonist inhibitor with therapeutic options for treating COVID-19 pending in vitro and in vivo validation.

Bioexploration and Phylogenetic Placement of Entomopathogenic Fungi of the Genus Beauveria in Soils of Lebanon Cedar Forests

The cedar forests of Lebanon have been threatened by the outbreak caused by climate change of a web-spinning sawfly, Cephalcia tannourinensis (Hymenoptera: Pamphiliidae), which negatively impacted the survival of one of the oldest tree species on earth. In this study, we investigated the occurrence of naturally soil-inhabiting entomopathogenic fungi for their role in containing the massive outbreak of this insect. We used a combination of fungal bioexploration methods, including insect bait and selective media. Morphological features and multilocus phylogeny-based on Sanger sequencing of the transcripts encoding the translation elongation factor 1-alpha (TEF-α), RNA polymerase II second largest subunit (RBP2), and the nuclear intergenic region (Bloc) were used for species identification. The occurrence rate of entomopathogenic fungi (EPF) varied with location, soil structure, forest structure, and isolation method. From 15 soil samples positive for fungal occurrence, a total of 249 isolates was obtained from all locations using different isolation methods. The phylogenetic analysis confirmed the existence of two novel indigenous species: Beauveria tannourinensis sp. nov. and Beauveria ehdenensis sp. nov. In conclusion, the present survey was successful (1) in optimizing the isolation methods for EPF, (2) investigating the natural occurrence of Beauveria spp. in outbreak areas of C. tannourinensis, and (3) in characterizing the presence of new Beauveria species in Lebanese cedar forest soil.

First evidence of the activity of an entomopathogenic fungus against the eggs of Sarcoptes scabiei

The entomopathogenic fungus Beauveria bassiana has been successfully used for the control of phytopathogenic arthropods and there are a growing number of studies suggesting that this kind of fungus could also be used for the control of ectoparasites in mammals. This study evaluated for the first time the efficacy of different Beauveria strains against the eggs of Sarcoptes scabiei collected from experimentally infected pigs. Eggs were exposed to fungal conidia and monitored for hatching over 10 days. The strongest effect (28.75 % of hatching inhibition) was obtained with a commercial B. bassiana strain. Furthermore, the detection of fungal genomic within the surface-cleaned eggs demonstrated the ability of B. bassiana to penetrate and proliferate in the egg-shell of S. scabiei. This study provides the first evidence, using molecular techniques, that the development of mycoacaricides may be of interest for the control of S. scabiei infection.

Sarcoptes Infestation. What Is Already Known, and What Is New about Scabies at the Beginning of the Third Decade of the 21st Century?

Currently, there are three known subtypes of scabies: ordinary, crusted, and bullous. The worldwide prevalence of scabies remains high in the 21st century. To decrease the social, economic, and psychological impact on the enormous population infected, a lot of important work has been completed over the last 20 years concerning the management of scabies. For example, a standardization of guidelines for the treatment of scabies has been completed and programs have been designed for the prevention and treatment in endemic populations, called mass drug administrations. Unfortunately, these only apply to the ordinary form of scabies. Moreover, resistance to the drugs currently used in treatment is growing, which imposes the need to search for new treatments. For this purpose, new acaricides are being developed to enhance the therapeutic options for the patients' benefit and effectively treat this disease. There is also the necessity for prevention before the development of scabies. An effective vaccine has the potential to protect people before this disease, especially in endemic areas. Unfortunately, there are no such vaccines against Sarcoptes yet.

Entomopathogenic Fungi and Bacteria in a Veterinary Perspective

Simple Summary

Several fungal species are well suited to control arthropods, being able to cause epizootic infection among them and most of them infect their host by direct penetration through the arthropod’s tegument. Most of organisms are related to the biological control of crop pests, but, more recently, have been applied to combat some livestock ectoparasites. Among the entomopathogenic bacteria, Bacillus thuringiensis, innocuous for humans, animals, and plants and isolated from different environments, showed the most relevant activity against arthropods. Its entomopathogenic property is related to the production of highly biodegradable proteins. Entomopathogenic fungi and bacteria are usually employed against agricultural pests, and some studies have focused on their use to control animal arthropods. However, risks of infections in animals and humans are possible; thus, further studies about their activity are necessary.

Abstract

The present study aimed to review the papers dealing with the biological activity of fungi and bacteria against some mites and ticks of veterinary interest. In particular, the attention was turned to the research regarding acarid species, Dermanyssus gallinae and Psoroptes sp., which are the cause of severe threat in farm animals and, regarding ticks, also pets. Their impact on animal and human health has been stressed, examining the weaknesses and strengths of conventional treatments. Bacillus thuringiensis, Beauveria bassiana and Metarhizium anisopliae are the most widely employed agents. Their activities have been reviewed, considering the feasibility of an in-field application and the effectiveness of the administration alone or combined with conventional and alternative drugs is reported.

Beauvericin potentiates the activity of pesticides by neutralizing the ATP-binding cassette transporters in arthropods

Multi-drug resistance is posing major challenges in suppressing the population of pests. Many herbivores develop resistance, causing a prolonged survival after exposure to a previously effective pesticide. Consequently, resistant pests reduce the yield of agricultural production, causing significant economic losses and reducing food security. Therefore, overpowering resistance acquisition of crop pests is a must. The ATP binding cassette transporters (ABC transporters) are considered as the main participants to the pesticide efflux and their neutralization will greatly contribute to potentiate failed treatments. Real-Time PCR analysis of 19 ABC transporter genes belonging to the ABCB, ABCC, ABCG, and ABCH revealed that a broad range of efflux pumps is activated in response to the exposure to pesticides. In this study, we used beauvericin (BEA), a known ABC transporters modulator, to resensitize different strains of Tetranychus urticae after artificial selection for resistance to cyflumetofen, bifenazate, and abamectin. Our results showed that the combinatorial treatment of pesticide (manufacturer's recommended doses) + BEA (sublethal doses: 0.15 mg/L) significantly suppressed the resistant populations of T. urticae when compared to single-drug treatments. Moreover, after selective pressure for 40 generations, the LC₅₀ values were significantly reduced from 36.5, 44.7, and 94.5 (pesticide) to 8.3, 12.5, and 23.4 (pesticide + BEA) for cyflumetofen, bifenazate, and abamectin, respectively. While the downstream targets for BEA are still elusive, we demonstrated hereby that it synergizes with sub-lethal doses of different pesticides and increases their effect by inhibiting ABC transporters. This is the first report to document such combinatorial activity of BEA against higher invertebrates paving the way for its usage in treating refractory cases of resistance to pesticides. Moreover, we demonstrated, for the first time, using in silico techniques, the higher affinity of BEA to ABC transformers subfamilies when compared to xenobiotics; thus, elucidating the pathway of the mycotoxin.