Biofilm inhibition effect of an ivermectin/silyl acrylate copolymer coating and the colonization dynamics

Repurposing Selamectin as an Antimicrobial Drug against Hospital-Acquired Staphylococcus aureus Infections

The emergence of multidrug-resistant strains requires the urgent discovery of new antibacterial drugs. In this context, an antibacterial screening of a subset of anthelmintic avermectins against gram-positive and gram-negative strains was performed. Selamectin completely inhibited bacterial growth at 6.3 μg/mL concentrations against reference gram-positive strains, while no antibacterial activity was found against gram-negative strains up to the highest concentration tested of 50 μg/mL. Given its relevance as a community and hospital pathogen, further studies have been performed on selamectin activity against Staphylococcus aureus (S. aureus), using clinical isolates with different antibiotic resistance profiles and a reference biofilm-producing strain. Antibacterial studies have been extensive on clinical S. aureus isolates with different antibiotic resistance profiles. Mean MIC90 values of 6.2 μg/mL were reported for all tested S. aureus strains, except for the macrolide-resistant isolate with constitutive macrolide-lincosamide-streptogramin B resistance phenotype (MIC90 9.9 μg/mL). Scanning Electron Microscopy (SEM) showed that selamectin exposure caused relevant cell surface alterations. A synergistic effect was observed between ampicillin and selamectin, dictated by an FIC value of 0.5 against methicillin-resistant strain. Drug administration at MIC concentration reduced the intracellular bacterial load by 81.3%. The effect on preformed biofilm was investigated via crystal violet and confocal laser scanning microscopy. Selamectin reduced the biofilm biomass in a dose-dependent manner with minimal biofilm eradication concentrations inducing a 50% eradication (MBEC50) at 5.89 μg/mL. The cytotoxic tests indicated that selamectin exhibited no relevant hemolytic and cytotoxic activity at active concentrations. These data suggest that selamectin may represent a timely and promising macrocyclic lactone for the treatment of S. aureus infections.

Hydrophobic DES Based on Menthol and Natural Organic Acids for Use in Antifouling Marine Coatings

Marine biofouling negatively impacts industries with off-shore infrastructures, such as naval, oil, and aquaculture. To date, there are no ideal sustainable, economic, and environmentally benign solutions to deal with this phenomenon. The advances achieved in green solvents, as well as its application in different industries, such as pharmaceutical and biotechnology, have promoted the emergence of deep eutectic systems (DES). These eutectic systems have applications in various fields and can be revolutionary in the marine-based industrial sector. In this study, the main objective was to investigate the potential use of hydrophobic DES (HDES) based on menthol and natural organic acids for their use as marine antifouling coatings. Our strategy encompassed the physicochemical characterization of different formulations, which allowed us to identify the most appropriate molar ratio and intermolecular interactions for HDES formations. The miscibility of the resulting HDES with the marine coating has been evaluated and proven to be successful. The Men/OL (1:1) system proved to be the most promising in terms of cost-production and thus was the one used in subsequent antifouling tests. The cytotoxicity of this HDES was evaluated using an in vitro cell model (HaCat cells) showing no significant toxicity. Furthermore, the application of this system incorporated into coatings that are used in marine structures was also studied using marine species (Mytilus edulis mussels and Patella vulgata limpets) to evaluate both their antifouling and ecotoxicity effects. HDES Men/OL (1:1) incorporated in marine coatings was promising in reducing marine macrofouling and also proved to be effective at the level of microfouling without viability impairment of the tested marine species. It was revealed to be more efficient than using copper oxide, metallic copper, or ivermectin as antifouling agents. Biochemical assays performed on marine species showed that this HDES does not induce oxidative stress in the tested species. These results are a strong indication of the potential of this HDES to be sustainable and efficiently used in marine fouling control technologies.

How do environmentally friendly antifouling alkaloids affect marine fouling microbial communities?

Most previous studies on antifouling (AF) agents have focused on the influence of biofilm formation constituted by single or multiple cultured microbial species, and very few studies have analyzed the relationship between environmentally friendly AF compounds and marine fouling microbial communities (MFMCs). This is the first investigation of the impact of three environmentally friendly alkaloids (5-chlorosclerotiamide, circumdatin F and notoamide C) produced by the deep-sea-derived fungus Aspergillus westerdijkiae on MFMCs using high-throughput Illumina sequencing in a field test. The results of this study showed that the three alkaloids could significantly decrease the coverage of marine microflora (p < 0.05) and affect the composition and diversity of MFMCs on polyvinyl chloride (PVC) plates. Furthermore, 5-chlorosclerotiamide and notoamide C could completely inhibit many macrofouler-inductive-bacteria, such as Pseudoalteromonas and Pseudomonas, and promote the anti-macrofouler-bacteria, such as Winogradskyella, from 0.21% to more than 10% of the MFMCs on PVC plates. These results suggested that 5-chlorosclerotiamide and notoamide C could influence the compositions of MFMCs and make it unfavorable for the settlement of macrofoulers, by reducing the abundance of macrofouler-inductive-bacteria and promoting the percentage of anti-macrofouler-bacteria on PVC plates. The present study provides a new way to evaluate the effect of environmentally friendly AF compounds and obtain a better understanding of the antifouling process.

The threat of veterinary medicinal products and biocides on pollinators: A One Health perspective

The One Health approach acknowledges that human health is firmly linked to animal and environmental health. It involves using animals such as bees and other pollinators as sentinels for environmental contamination or biological indicators. Beekeepers noticed intoxications of apiaries located in the vicinity of sheep and cattle farms, which led to the suspicion of bees' intoxication by the products used for livestock: veterinary medicinal products (VMPs) and Biocides, confirmed by laboratory analysis. We review the legal context of VMPs and Biocidal products considering Europe as a case study, and identify shortcomings at the environmental level. We describe the possible ways these products could intoxicate bees in the vicinity of livestock farms. We also illustrate the way they may impact non-target species. The cases of ivermectin and abamectin as VMPs, deltamethrin and permethrin as Biocides are considered as case studies. We show bees can be exposed to new and unrecognized routes of exposure to these chemicals, and demonstrate that their application in livestock farming can affect the survival of pollinators, such as bees. We conclude that: (1) figures on the marketing/use of these chemicals should be harmonized, centralized and publicly available, (2) research should be devoted to clarifying how pollinators are exposed to VMPs and Biocides, (3) toxicity studies on bees should be carried out, and (4) pollinators should be considered as non-targeted species concerning the environmental risk assessment before their marketing authorization. We propose the term "Multi-use substances" for active ingredients with versatile use.

Biomimetic surface coatings for marine antifouling: Natural antifoulants, synthetic polymers and surface microtopography

Marine biofouling is a ubiquitous problem that accompanies human marine activities and marine industries. It exerts detrimental impacts on the economy, environment, ecology, and safety. Traditionally, mainstream approaches utilize metal ions to prevent biological contamination, but this also leads to environmental pollution and damage to the ecosystem. Efficient and environmentally friendly coatings are urgently needed to prevent marine devices from biofouling. Since nature is always the best teacher for humans, it offers us delightful thoughts on the research and development of high-efficiency, broad-spectrum and eco-friendly antifouling coatings. In this work, we focus on the research frontier of marine antifouling coatings from a bionic perspective. Enlightened by three distinctive dimensions of bionics: chemical molecule bionic, physiological mechanism bionic, and physical structure bionic, the research status of three main bioinspired strategies, which are natural antifoulants, bioinspired polymeric antifouling coatings, and biomimetic surface microtopographies, respectively, are demonstrated. The antifouling mechanisms are further interpreted based on biomimetic comprehension. The main fabrication methods and antifouling performances of these coatings are presented along with their advantages and drawbacks. Finally, the challenges are summarized, and future research prospects are proposed. It is believed that biomimetic antifouling strategies will contribute to the development of nontoxic antifouling techniques with exceptional repellency and stability.

Biodegradation of tetracycline using hybrid material (UCPs-TiO2) coupled with biofilms under visible light

To develop a more green and effective method for tetracycline (TC) removal, a hybrid material (conversion phosphors-TiO₂, UCPs-TiO₂) was coupled with a biofilm to achieve enhanced removal of TC. The removal of TC by biofilm coupled with UCPs-TiO₂ under visible light reached 82%, which was 35% higher than that in treatment using only the biofilm. Extracellular polymeric substance (EPS) promoted the production of hydroxyl radicals by UCPs-TiO₂, as the EPS acted as an electron transfer medium and accelerated the TC mineralization. Biofilm in the coupled system tolerated TC stress by regulating its antibiotic resistance genes (ARG) and superoxidedismutase (SOD), and allowed it to maintain stable and efficient removal of TC. This study documents a method to couple a hybrid material with microbial aggregates, creating a promising system for removing refractory organics, such as TC, from water. The study also offers insight into the mechanisms underlying TC removal by microbial aggregates combined with new functional materials.

Research progress of environmentally friendly marine antifouling coatings

The antifouling mechanisms and research progress in the past three years of environmentally friendly marine antifouling coatings are introduced in this work.