Phenotypic and genotypic comparison of antimicrobial-resistant variants of Escherichia coli and Salmonella Typhimurium isolated from evolution assays with antibiotics or commercial products based on essential oils

On account of the widespread development and propagation of antimicrobial-resistant (AMR) bacteria, essential oils (EOs) have emerged as potential alternatives to antibiotics. However, as already observed for antibiotics, recent studies have raised concerns regarding the potential emergence of resistant variants (RVs) to EOs. In this study, we assessed the emergence of RVs in Escherichia coli and Salmonella enterica Typhimurium after evolution assays under extended exposure to subinhibitory doses of two commercial EOs (AEN and COLIFIT) as well as to two antibiotics (amoxicillin and colistin). Phenotypic characterization of RVs from evolution assays with commercial EOs yielded no relevant increases in the minimum inhibitory concentration (MIC) of E. coli and did not even modify MIC values in S. Typhimurium. Conversely, RVs of E. coli and S. Typhimurium isolated from evolution assays with antibiotics showed increased resistance. Genotypic analysis demonstrated that resistance to commercial EOs was associated with enhanced protection against oxidative stress and redirection of cell energy toward efflux activity, while resistance to antibiotics was primarily linked to modifications in the cell binding sites of antibiotics. These findings suggest that AEN and COLIFIT could serve as safe alternatives to antibiotics in combating the emergence and dissemination of antimicrobial resistance within the agrifood system

Lethal and sublethal effects of carlina oxide on Tetranychus urticae (Acari: Tetranychidae) and Neoseiulus californicus (Acari: Phytoseiidae)

BACKGROUND: Tetranychus urticae Koch, is a polyphagous and damaging pest, presenting several resistant populations world- wide. Among new and more environmentally friendly control tools, botanical pesticides represent a valuable alternative to syn- thetic ones within integrated pest management strategies. Accordingly, we investigated the lethal and sublethal effects of carlina oxide isolated from Carlina acaulis (Asteraceae) roots on T. urticae and its natural enemy, the predatory mite, Neoseiulus californicus (McGregor). RESULTS: Carlina oxide (98.7% pure compound) was used for acaricidal tests on eggs, nymphs, and adult females of T. urticae (concentrations of 312.5, 625, 1250, 2500 and 5000 !L L!1), and eggs and females of N. californicus (1250 and 5000 !L L!1 on eggs and females, respectively). Behavioral two-choice tests were also conducted on phytoseiid females. Carlina oxide toxicity was higher on T. urticae females than nymphs (median lethal dose 1145 and 1825 !L L!1, respectively), whereas egg mortality and mean hatching time were signi!cantly affected by all tested concentrations. A decreasing daily oviposition rate for T. urticae was recorded with concentrations ranging from 625 to 5000 !L L!1, whereas negative effects on the population growth rate were recorded only with the three higher concentrations (1250, 2500 and 5000 !L L!1). No toxic effect on N. californicus females was found, but a strong repellent activity lasting for 48 h from application was recorded. CONCLUSION: Carlina oxide reduced longevity and fecundity of T. urticae adults, but not of N. californicus. This selective prop- erty allows us to propose it as a novel active ingredient of ecofriendly acaricides for T. urticae management

Aniseed, Pimpinella anisum, as a source of new agrochemicals: phytochemistry and insights on insecticide and acaricide development

Pimpinella anisum L. (Apiaceae), known around the world as aniseed, is a widely cultivated crop, native of the sub-Mediterranean area. Its essential oil (EO) is exploitable in different fields such as food and beverages, pharmaceutics, cosmetics, and nutraceuticals. Regardless of the geographic origin, the EO exhibited consistent transanethole predominancy. Among the numerous biological properties exerted by aniseed EO, its antimicrobial, antifungal, insecticidal, and acaricidal effects have been extensively investigated for the formulation of biopesticides against larvae and adults of various pests and vectors. Hereafter, the published data on the insecticidal and acaricidal activity of aniseed EO and its major compounds on agricultural pests, stored-product pests, and arthropods of medical and veterinary interest is reviewed. For each study, the arthropod and the developmental stage on which the aniseed EO or the aniseed EO-based formulation were tested, the mode of action, the main constituents, and the exerted mortality, as well as the toxicity to non-target organisms and the possible sub-lethal effects are reported. The advantages of the possible use of aniseed EO as a biopesticide are analysed, as well as the current weaknesses and the critical points to be overcome to open the doors to the industrial utilization of Apiaceae EOs by the agrochemical industry

Trehalose Effect on the Aggregation of Model Proteins into Amyloid Fibrils

Protein aggregation into amyloid fibrils is a phenomenon that attracts attention from a wide and composite part of the scientific community. Indeed, the presence of mature fibrils is associated with several neurodegenerative diseases, and in addition these supramolecular aggregates are considered promising self-assembling nanomaterials. In this framework, investigation on the effect of cosolutes on protein propensity to aggregate into fibrils is receiving growing interest, and new insights on this aspect might represent valuable steps towards comprehension of highly complex biological processes. In this work we studied the influence exerted by the osmolyte trehalose on fibrillation of two model proteins, that is, lysozyme and insulin, investigated during concomitant variation of the solution ionic strength due to NaCl. In order to monitor both secondary structures and the overall tridimensional conformations, we have performed UV spectroscopy measurements with Congo Red, Circular Dichroism, and synchrotron Small Angle X-ray Scattering. For both proteins we describe the effect of trehalose in changing the fibrillation pattern and, as main result, we observe that ionic strength in solution is a key factor in determining trehalose efficiency in slowing down or blocking protein fibrillation. Ionic strength reveals to be a competitive element with respect to trehalose, being able to counteract its inhibiting effects toward amyloidogenesis. Reported data highlight the importance of combining studies carried out on cosolutes with valuation of other physiological parameters that may affect the aggregation process. Also, the obtained experimental results allow to hypothesize a plausible mechanism adopted by the osmolyte to preserve protein surface and prevent protein fibrillation

Anti-inflammatory activities of spilanthol-rich essential oil from Acmella oleracea and its nanoemulsion in the prevention of neurodegenerative disorders

Neurodegenerative diseases are a health problem that is growing more and more worldwide. As these pathologies mainly affect the elderly, their incidence is closely related to the increase in the average life span of the population. These pathologies are characterized by a multifactorial etiology involving common triggering causes like excitotoxicity, mitochondrial disfunction, accumulation of misfolded proteins, oxidative stress and inflammation. Among these, the neuroinflammatory process is emergeing as a key factor in the genesis of these pathologies. Microglia, through the production of pro-inflammatory and anti-inflammatory mediators, is essential in maintaining tissue homeostasis and physiological brain development. However, excessive microglial cells activation produces a large number of cytokines and reactive oxygen species (ROS) causing progressive neuronal loss[1]. Therefore, the modulation of pro- inflammatory molecules from microglia could be a promising strategy to counteract neurodegeneration. Acmella oleracea (L.), a medicinal plant native to Brazil, is known and exploited worldwide in traditional medicine for its pharmacological properties, which seem mainly related to its main secondary metabolite, the alkylamide spilanthol. Spilanthol showed various biological properties such as antimicrobial, diuretic, hepatoprotective, insecticidal, antinociceptive, analgesic, anti-inflammatory and antioxidant activities[2]. The aim of this study was to investigate the anti-inflammatory properties of a spilanthol-rich essential oil obtained with a microwave-assisted extraction method on A. oleracea aerial parts (AO) in BV-2 microglial cells. Cells were treated with different concentrations of AO, pure spilanthol (S) or a nanoemulsion (NE) containing AO for 24 h and then activated by to LPS (100 ng/mL). Cell viability, measured by MTT assay, was significantly increased by all treatments with respect to cells only exposed to LPS. Of note, AO and NE also decreased ROS levels measured by DCFH-DA assay, while S had no effect on this parameter. To better characterize the anti-inflammatory activity of AO, the expression of inflammatory mediators such as IL-1b, TNF-, COX-2 and iNOS was investigated by RT-PCR. Interestingly, all the treatments were able to reduce the LPS-induced up-regulation of these inflammatory mediators. These results suggest that AO potentially could be used as therapeutic agent in neurodegenerative diseases due to its antioxidant and anti-inflammatory properties. This work also evidences a promising application of NE as a new technological formulation to further increase the bioavailability of this essential oil

Efficacy of <i>Mentha aquatica</i> L. Essential Oil (Linalool/Linalool Acetate Chemotype) against Insect Vectors and Agricultural Pests

In recent years, agrochemical industries have been focused on the development of essential oil (EO)-based biopesticides, which can be considered valuable alternatives to traditional chemical products. The genus Mentha (Lamiaceae) comprises 30 species characterized by a wide range of biological activities, and some of their EOs showed good potential as pesticidal agents. In this regard, the aim of this study was to evaluate the insecticidal activity of the EO obtained from a rare linalool/linalool acetate chemotype of Mentha aquatica L. The EO was found to be highly effective against Culex quinquefasciatus (Say) 2nd instar larvae, Metopolophium dirhodum (Walker) adults, Spodoptera littoralis (Boisduval) 2nd instar larvae, and Tetranychus urticae (Koch) adults, showing lethal concentrations (LC50) or doses (LD50) of 31.5 ± 2.2 µL L−1, 4.9 ± 0.8 mL L−1, 18.5 ± 2.1 µg larvae−1, and 3.3 ± 0.5 mL L−1, respectively. On the contrary, Musca domestica L. adults and 3rd instar larvae of C. quinquefasciatus and S. littoralis were moderately affected by the treatment (LC50 or LD50: 71.4 ± 7.2 µg adult−1, 79.4 ± 5.2 µL L−1, 44.2 ± 5.8 µg larvae−1, respectively). The results obtained in this work demonstrated that various insects and pests could be differently sensible to the same EO and may lead to the exploitation of this plant or its major volatile compounds as novel ingredients of botanical insecticides and pesticides

Microwave-Assisted Hydrodistillation of the Insecticidal Essential Oil from Carlina acaulis: A Fractional Factorial Design Optimization Study

Recently, microwave-assisted hydrodistillation (MAH) has been reported as an innovative technique leading to increased essential oil (EO) extraction yield, coupled with reduced extraction time and energy costs. The EO of Carlina acaulis L. (Asteraceae), mainly constituted by carlina oxide (&gt;95%) and conventionally obtained through traditional hydrodistillation (HD), has been reported as extremely effective against several arthropod vectors and pests of medical and economic importance with limited impact on non-target species, including mammals. This study aimed to the optimization of the EO extraction through MAH by using a one-step design of experiments (DoE) approach that allowed us to relate the characteristics of the produced EOs with the applied experimental conditions using mathematical models. The preliminary screening allowed us to optimize the protocol only by the extraction time, skipping complex data analysis. Moreover, the comparison of the optimized MAH conditions with traditional HD pointed out the higher efficiency of MAH in terms of EO yield (0.65 and 0.49% for MAH and HD, respectively) and extraction time (210 min for MAH). The results obtained confirmed the promising role that MAH could have in C. acaulis EO extraction, with increased yield and reduced extraction time, water consumption, and energy costs, and being employable on an industrial scale, with special reference to insecticidal and acaricidal formulations

A Review of the Chemistry and Biological Activities of <i>Acmella oleracea</i> (“jambù”, Asteraceae), with a View to the Development of Bioinsecticides and Acaricides

Human pathologies, environmental pollution, and resistance phenomena caused by the intensive use of chemical pesticides have shifted the attention of the agrochemical industries towards eco-friendly insecticides and acaricides. Acmella oleracea (L.) R. K. Jansen (jambù) is a plant native to South America, widely distributed and cultivated in many countries due to its numerous pharmacological properties. This review analyzes literature about the plant, its uses, and current knowledge regarding insecticidal and acaricidal activity. Acmella oleracea has proven to be a potential pesticide candidate against several key arthropod pest and vector species. This property is inherent to its essential oil and plant extract, which contain spilanthol, the main representative of N-alkylamides. As a result, there is a scientific basis for the industrial exploitation of jambù in the preparation of green insecticides. However, studies related to its toxicity towards non-target species and those aimed at formulating and developing marketable products are lacking

Essential oil-based nanoinsecticides: ecological costs and commercial potential

The present chapter offers an updated overview on the practical employ of EO-based nanoinsecticides, with a major focus on their ecological costs and commercial potential. Starting from the characteristics and bioactivity information on plant EOs, we analyze (1) the advantages and challenges arising from the use of EOs for insect pest control, (2) status and limitations of the EO commercial applications and marketability; (3) the EO-based insecticide nanoformulations currently available (both nanoemul- sions and nanostructures, e.g., chitosan particles, liposomes, polyethylene glycol (PEG) nanoparticles, cyclodextrin inclusion complexes), their strengthens and weaknesses; (4) the ecological costs and constraints of EO-based nanoinsecticides, in terms of nontarget impacts, sustainability of production, land use and consume, and the related commercial perspectives. In the conclusions, challenges for future research are proposed