Effect of Adding Red Propolis to Edible Biodegradable Protein Films for Coating Grapes: Shelf Life and Sensory Analysis.

Red propolis is an active ingredient of great nutritional interest which offers numerous benefits as an antioxidant and antimicrobial agent. Thus, the objective of this research was to evaluate the application of an edible and antimicrobial gelatine coating containing red propolis to increase the shelf life of grapes. Gelatine films with an addition of 5, 10, 15, 20 and 25% of red propolis extract were produced to evaluate their antimicrobial activity using the disk diffusion test in solid media. The films with 25% red propolis extract showed antimicrobial activity against the bacteria Staphylococcus aureus and Pseudomonas aeruginosa. The grapes were coated with pure gelatine, without a plasticizer and with gelatine with 25% red propolis and then stored for 1, 4, 10, 19 and 25 days at temperatures of 25 °C and 5 °C. The results showed that the gelatine coating with propolis reduced the mass loss of grapes stored at 25 °C for 19 days by 7.82% and by 21.20% for those kept at 5 °C for 25 days. The pH, total titratable acidity, soluble solids and color of the grapes increased due to the ripening process. Furthermore, the sensory acceptability indexes of the refrigerated grapes with coatings were superior (>78%) to those of the control samples (38%), proving the effectiveness of the coatings in maintaining the quality of grapes during storage.

Activity of biogenic silver nanoparticles in planktonic and biofilm-associated Corynebacterium pseudotuberculosis.

Corynebacterium pseudotuberculosis is a gram-positive bacterium and is the etiologic agent of caseous lymphadenitis (CL) in small ruminants. This disease is characterized by the development of encapsulated granulomas in visceral and superficial lymph nodes, and its clinical treatment is refractory to antibiotic therapy. An important virulence factor of the Corynebacterium genus is the ability to produce biofilm; however, little is known about the characteristics of the biofilm produced by C. pseudotuberculosis and its resistance to antimicrobials. Silver nanoparticles (AgNPs) are considered as promising antimicrobial agents, and are known to have several advantages, such as a broad-spectrum activity, low resistance induction potential, and antibiofilm activity. Therefore, we evaluate herein the activity of AgNPs in C. pseudotuberculosis, through the determination of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), antibiofilm activity, and visualization of AgNP-treated and AgNP-untreated biofilm through scanning electron microscopy. The AgNPs were able to completely inhibit bacterial growth and inactivate C. pseudotuberculosis at concentrations ranging from 0.08 to 0.312 mg/mL. The AgNPs reduced the formation of biofilm in reference strains and clinical isolates of C. pseudotuberculosis, with interference values greater than 80% at a concentration of 4 mg/mL, controlling the change between the planktonic and biofilm-associated forms, and preventing fixation and colonization. Scanning electron microscopy images showed a significant disruptive activity of AgNP on the consolidated biofilms. The results of this study demonstrate the potential of AgNPs as an effective therapeutic agent against CL.

Cryptocarya moschata extract decreases single and mixed biofilms on acrylic resins.

OBJECTIVE: This study proposed to assess the effect of Cryptocarya moschata extract on single and mixed biofilms formed on denture base and reline acrylic resin. MATERIALS AND METHODS: Single and mixed biofilms of Candida albicans and Streptococcus mutans were formed on the samples and treated with C. moschata extract; Nystatin solution at 100,000 IU/mL or Penicillin antibiotic solution at 100,000 IU/mL; or PBS solution. Antimicrobial activity was analyzed by counting colony-forming units, metabolism assay, assessment of protein components of the biofilm matrix, and of cell viability using confocal laser scanning microscopy (CLSM). Data were submitted to ANOVA and Tukey's post-test (α = 0.05). RESULTS: Cryptocarya moschata extract reduced cell viability of C. albicans and S. mutans single and mixed biofilms formed on samples. For all types of biofilms in the C. moschata group, there was a log reduction of the biofilm, proven by the Alamar Blue assay. Analyzing the extracellular matrix protein components, groups treated with the extract exhibited a lower level of fluorescence compared to the PBS groups. Reduction in thickness biofilm and viable cells was perceptible in the C. moschata group when assessing through CLSM. CONCLUSION: Cryptocarya moschata extract reduced the single and mixed biofilms of C. albicans and S. mutans on acrylic resins.

Antimicrobial evaluation of silver nanoparticles using extracts of Crescentia cujete L / Avaliação antimicrobiana de nanopartículas de prata usando extratos de Crescentia cujete L

New natural reducing agents with a lower negative impact on the environment and with a high antimicrobial potential are required for the process of obtaining silver nanoparticles through the chemical reduction method. The use of plant extracts can be a fast track in the formation of nanoparticles. In this case, organic compounds such as terpenes, flavonoids, enzymes, proteins, and cofactors present in plants act as reducing agents for nanomaterials. This research evaluated the antimicrobial property of silver nanoparticles from extracts of Crescentia cujete L. The presence of quercetin (flavonoid) was determined by high-performance liquid chromatography (HPLC); the production of silver nanoparticles (AgNPs) was established by green synthesis; the size and morphology of the nanomaterials were evaluated by scanning electron microscope (SEM). The antimicrobial capacity was studied by two analysis methods: modified culture medium and surface seeding. The presence of quercetin (26.55 mg L-1) in the crude extract of Crescentia cujete L., identified by HPLC, was evidenced. Nanoparticle formation was spherical, with an average size of 250 ± 3 and 460 ± 6 nm. Microbiological cultures with treatment showed 94% microbial inhibition. It was concluded that the Crescentia cujete L., leaves shoed an acceptable concentration of quercetin to be used as a useful adjuvant to enhance the reduction of NPs synthesis. The nanoparticles produced by green synthesis proved to have a positive effect to combat pathogenic microorganisms.

Novos agentes redutores naturais com menor impacto negativo ao meio ambiente e com alto potencial antimicrobiano são necessários para o processo de obtenção de nanopartículas de prata, pelo método de redução química. O uso de extratos vegetais pode ser um caminho rápido na formação de nanopartículas. Nesse caso, compostos orgânicos como terpenos, flavonoides, enzimas, proteínas e cofatores presentes nas plantas atuam como agentes redutores dos nanomateriais. Esta pesquisa avaliou a propriedade antimicrobiana de nanopartículas de prata de extratos de Crescentia cujete L. A presença de quercetina (flavonoide) foi determinada por cromatografia líquida de alta eficiência (HPLC); a produção de nanopartículas de prata (AgNPs) foi estabelecida por síntese verde; o tamanho e a morfologia dos nanomateriais foram avaliadas dos por microscópio eletrônico de varredura (SEM). A capacidade antimicrobiana foi estudada por dois métodos de análise: meio de cultura modificado e semeadura em superfície. Foi evidenciada a presença de quercetina (26,55 mg L-1) no extrato bruto de Crescentia cujete L., identificada por HPLC. A formação das nanopartículas foi esférica, com tamanho médio de 250 ± 3 e 460 ± 6 nm. Culturas microbiológicas com tratamento mostraram 94% de inibição microbiana. Assim, concluiu-se que as folhas de Crescentia cujete L. apresentam uma concentração aceitável de quercetina para ser utilizada como um adjuvante útil para potencializar a redução da síntese de NPs. As nanopartículas produzidas pela síntese verde provaram ter um efeito positivo no combate a microrganismos patogênicos.

Profile of Antimicrobial Consumption in Patients Assisted by a Palliative Care Team During the COVID-19 Pandemic in Brazil.

BACKGROUND: This study aimed to evaluate the profile of antimicrobial consumption in patients assisted by a palliative care (PC) team during the COVID-19 pandemic. METHODS: A retrospective observational study was conducted in a quaternary hospital. Patients assisted by the PC team in 2020 were selected. The clinical and demographic characteristics, as well as the outcomes, were assessed using electronic records. RESULTS: A total of 181 patients were included in the study, of whom 93.4% had used antimicrobials and 24.3% had had COVID-19. COVID-19 patients were more likely to receive at least one course of antimicrobial therapy. Patients who received polytherapy in the first course of treatment were more likely to die and to be still receiving antimicrobials at death. There was no significant difference in the length of hospital stay, new hospitalization in 12 months, nor the time to death among patients who received monotherapy or polytherapy during the first course of antimicrobial therapy. CONCLUSIONS: There was a large amount of PC patients receiving antimicrobial therapy during the COVID-19 pandemic. SARS-CoV-2-positive patients were more likely to receive antimicrobial therapy.

Toxicity Mechanisms of Copper Nanoparticles and Copper Surfaces on Bacterial Cells and Viruses.

Copper is a metal historically used to prevent infections. One of the most relevant challenges in modern society are infectious disease outbreaks, where copper-based technologies can play a significant role. Currently, copper nanoparticles and surfaces are the most common antimicrobial copper-based technologies. Despite the widespread use of copper on nanoparticles and surfaces, the toxicity mechanism(s) explaining their unique antimicrobial properties are not entirely known. In general, toxicity effects described in bacteria and fungi involve the rupture of membranes, accumulation of ions inside the cell, protein inactivation, and DNA damage. A few studies have associated Cu-toxicity with ROS production and genetic material degradation in viruses. Therefore, understanding the mechanisms of the toxicity of copper nanoparticles and surfaces will contribute to developing and implementing efficient antimicrobial technologies to combat old and new infectious agents that can lead to disease outbreaks such as COVID-19. This review summarizes the current knowledge regarding the microbial toxicity of copper nanoparticles and surfaces and the gaps in this knowledge. In addition, we discuss potential applications derived from discovering new elements of copper toxicity, such as using different molecules or modifications to potentiate toxicity or antimicrobial specificity.

Gold-, silver- and magnesium-doped zinc oxide nanoparticles prevents the formation of and eradicates bacterial biofilms.

Aim: This work aimed to synthesize magnesium-doped zinc oxide, silver and gold nanoparticles (Nps) and to evaluate their potential to prevent and eradicate Escherichia coli, Proteus mirabilis, Staphylococcus aureus, Acinetobacter baumannii and Pseudomonas aeruginosa biofilms. Materials & methods: The Nps were synthesized by precipitation and metallic reduction techniques. Physicochemical and biological characterization of Nps was performed. Results: All the Nps tested were able to inhibit the formation of E. coli, P. mirabilis, S. aureus and A. baumannii biofilms. The effects on the eradication of preformed biofilms were variable, although all the Nps tested were able to eradicate A. baumannii biofilms. Conclusion: The observed effects make the Nps suitable for coating surfaces and/or antibiotic carriers with medical interest.

Untargeted Metabolomics for Unraveling the Metabolic Changes in Planktonic and Sessile Cells of Salmonella Enteritidis ATCC 13076 after Treatment with Lippia origanoides Essential Oil.

Nontyphoidal Salmonella species are one of the main bacterial causes of foodborne diseases, causing a public health problem. In addition, the ability to form biofilms, multiresistance to traditional drugs, and the absence of effective therapies against these microorganisms are some of the principal reasons for the increase in bacterial diseases. In this study, the anti-biofilm activity of twenty essential oils (EOs) on Salmonella enterica serovar Enteritidis ATCC 13076 was evaluated, as well as the metabolic changes caused by Lippia origanoides thymol chemotype EO (LOT-II) on planktonic and sessile cells. The anti-biofilm effect was evaluated by the crystal violet staining method, and cell viability was evaluated through the XTT method. The effect of EOs was observed by scanning electron microscopy (SEM) analysis. Untargeted metabolomics analyses were conducted to determine the effect of LOT-II EO on the cellular metabolome. LOT-II EO inhibited S. Enteritidis biofilm formation by more than 60%, without decreasing metabolic activity. Metabolic profile analysis identified changes in the modulation of metabolites in planktonic and sessile cells after LOT-II EO treatment. These changes showed alterations in different metabolic pathways, mainly in central carbon metabolism and nucleotide and amino acid metabolism. Finally, the possible mechanism of action of L. origanoides EO is proposed based on a metabolomics approach. Further studies are required to advance at the molecular level on the cellular targets affected by EOs, which are promising natural products for developing new therapeutic agents against Salmonella sp. strains.

Chitosan as an Outstanding Polysaccharide Improving Health-Commodities of Humans and Environmental Protection.

Public health, production and preservation of food, development of environmentally friendly (cosmeto-)textiles and plastics, synthesis processes using green technology, and improvement of water quality, among other domains, can be controlled with the help of chitosan. It has been demonstrated that this biopolymer exhibits advantageous properties, such as biocompatibility, biodegradability, antimicrobial effect, mucoadhesive properties, film-forming capacity, elicitor of plant defenses, coagulant-flocculant ability, synergistic effect and adjuvant along with other substances and materials. In part, its versatility is attributed to the presence of ionizable and reactive primary amino groups that provide strong chemical interactions with small inorganic and organic substances, macromolecules, ions, and cell membranes/walls. Hence, chitosan has been used either to create new materials or to modify the properties of conventional materials applied on an industrial scale. Considering the relevance of strategic topics around the world, this review integrates recent studies and key background information constructed by different researchers designing chitosan-based materials with potential applications in the aforementioned concerns.

Evaluation of chitosan and silver nanoparticles Against isolated pathogens from Mulberry Silkworm, Bombyx mori L. (Lepidoptera: Bombycidae) under laboratory conditions / Avaliação de nanopartículas de quitosana e prata contra patógenos isolados de bicho-da-seda, Bombyx mori L. (Lepidoptera: Bombycidae), em condições de laboratório

This study aims to isolate and identify certain bactеrial and fungal pathogеns from silkworm, Bombyx mori L. such as promising chitosan, plus silvеr nanoparticlеs as its antimicrobial activity undеr laboratory condition. Silkworm, B. mori (H1xKKxG2xV2-Bolgaria) eggs werе attained from Sеriculture Rеsearch Cеntеr from Giza Governorate, Egypt. Chitosan and silvеr nanoparticlеs matеrials were assembled at the laboratory of Biochеmistry Departmеnt, Faculty of Agriculturе, Al-Azhar University, Cairo, Egypt. Herein total of 7 bactеrial and 5 fungal were isolatеd from the еxtеrnal and internal silkworm larvae. As a result, the mean percentage decrease in weight was elevated in diseased fifth instars (88%) compared to fourth diseased instars (62%). In addition, two bactеrial spеcies isolatеd from the infectеd larvae were identified as follows: Staphylococcus aurеus and Enterococcus faеcalis, whereas thrее fungal spеcies were isolatеd as follows: Aspergillus flavus, Aspergillus tamarii and Beauveria bassiana. Transmission elеctron microscopе imaging demonstrated the morphological propеrties and surfacе appеarance of silvеr and chitosan nanoparticlеs which havе a nеarly sphеrical shapе and smooth surfacе. The avеrage particlе size of 18.7 - 26.0 nm and 18.8 to 21.8 nm of silvеr and chitosan nanoparticles were recordеd. Furthermore, the highеst activity among nanoparticlеs tested against all pathogеnic bacteria and fungi isolatеd and idеntified in our study was rеcordеd by chitosan at 100 µg/ml in sеries, whilst silvеr nanoparticle еxhibitеd modеrate antibacterial and antifungal activity.

Este estudo visa isolar e identificar certos patógenos bacterianos e fúngicos do bicho-da-seda (Bombyx mori L.), como a promissora quitosana, além de nanopartículas de prata como sua atividade antimicrobiana em condições de laboratório. Ovos de B. mori (H1xKKxG2xV2-Bolgaria) foram obtidos do Centro de Pesquisa em Sericultura da Província de Gizé, Egito. Materiais de nanopartículas de quitosana e prata foram montados no laboratório do Departamento de Bioquímica, Faculdade de Agricultura, Universidade Al-Azhar, Cairo, Egito. Aqui, foi isolado um total de 7 bactérias e 5 fungos das larvas de bicho-da-seda externas e internas. Como resultado, a diminuição percentual média no peso foi elevada no quinto instar doente (88%) em comparação com o quarto instar doente (62%). Além disso, foram identificadas duas espécies bacterianas isoladas das larvas infectadas (Staphylococcus aureus e Enterococcus faecalis), enquanto três espécies fúngicas foram isoladas (Aspergillus flavus, Aspergillus tamarii e Beauveria bassiana). A imagem de microscopia eletrônica de transmissão demonstrou as propriedades morfológicas e aparência de superfície de nanopartículas de prata e quitosana que têm uma forma quase esférica e superfície lisa. Foi registrado o tamanho médio das partículas de 18,7-26,0 nm e 18,8-21,8 nm de nanopartículas de prata e quitosana, respectivamente. Além disso, a atividade mais alta entre as nanopartículas testadas contra todas as bactérias patogênicas e fungos isolados e identificados em nosso estudo foi registrada pela quitosana em 100 µg/ml em série, enquanto a nanopartícula de prata exibiu atividade antibacteriana e antifúngica moderada.

Co-occurrence of linear and cyclic pelgipeptins in broth cultures of Paenibacillus elgii AC13.

Paenibacillus elgii AC13 produces antimicrobial lipopeptides of agricultural and pharmaceutical importance. It secretes four cyclic lipopeptides named pelgipeptins, previously characterized in P. elgii B69. These lipopeptides result from the expression of a nonribosomal peptide gene cluster. P. elgii AC13 also produced two linear lipopeptides with ratios of [M + H] + 1105 and 1119 m/z. These compounds were previously observed in Paenibacillus sp. strain OSY-N, but due to purification difficulties, their characterization was executed using synthetically produced linear pelgipeptins. In the present study, purification was achieved from the supernatants of cultures from three complex media by high-performance liquid chromatography. The partial characterization of linear pelgipeptins revealed the similar antimicrobial activity and cytotoxicity of their synthetically produced counterparts, known as paenipeptins. Cyclic forms were highly stable to changes in pH, temperature, and organic extraction with n-butanol as shown by mass spectrometry (MALDI-TOF); therefore, these steps did not cause the hydrolysis of pelgipeptins. A low-activity thioesterase could also generate the linear isoforms observed; this enzyme catalyzes the cyclization process and is coded in the same gene cluster. Alternatively, the cyclic forms were hydrolyzed by an unknown protease produced during growth in the complex medium used in the present study. Although culture conditions are known to produce pelgipeptins with different yields and amino acid compositions, the occurrence of linear and cyclic forms simultaneously has not yet been reported. A mixture of cyclic and linear pelgipeptins presents a potential advantage of the higher antimicrobial activity of cyclic forms combined with the lower cytotoxicity of linear isoforms.

Benzoic acid complexes with Eudragit E100®: New alternative antimicrobial preservatives.

Given that the use of some preservatives in cosmetics has been restricted, novel alternative preservatives are needed. The aim of this study was to characterize the physicochemical and antimicrobial properties of two polyelectrolyte complexes (EuB100 and EuB75Cl25), which were developed through hot melt extrusion (HME) using benzoic acid (BA) and Eudragit E100. Based on phase diagrams and an experimental statistical design, the solubility of the acid in the polymer and the HME conditions were established. Intermolecular interactions were evaluated through Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRPD). Release behavior was determined for the systems. Antibacterial activity and ζ-potential were determined on Escherichia coli. FTIR revealed acid-base interaction, and XPS showed that the percentages of protonated nitrogen N1s were 13.5% for EuB100 and 20.3% for EuB75Cl25. The BA released showed a non-Fickian behavior, and a satisfactory antibacterial activity against E. coli was demonstrated at pH 6.9. The complexes modified ζ-potential, destabilizing the membrane functionality of E. coli. These complexes are potential antimicrobial preservatives with a greater spectrum of action, with bactericidal activity against E. coli in a wider pH range than uncomplexed BA, even at pH 6.9.

Study of the scientific production of the antibacterial activity of the chemical compounds of the essential oil of Lippia sidoides / Estudo da produção científica da atividade antibacteriana dos componentes químicos do óleo essencial de Lippia sidoides

Lippia sidoides Cham. has widespread use in folk medicine because its essential oil (EO) presents great antibacterial properties. In Brazil, this plant has been introduced in governmental programs for herbal medicine, due to its recognized therapeutic activities. This promoted greater interest in the search for new molecules with antimicrobial activity in this EO which have been described by several authors. Thus, this work aimed to present a study of the scientific production of antibacterial activity of the chemical compounds from L. sidoides essential oil (LSEO). The inclusion criteria were articles which assessed the chemical components and antibacterial activity through the inhibition diameter, Minimum Inhibitory Concentration (MIC), and Minimal Bactericidal Concentration (MBC), published between 2000 and 2020. Of the 996 studies identified, 55 met the inclusion criteria. In descending order, the most frequently detected chemical components found in LSEO were: thymol, p-cymene, and caryophillene. Regarding to the origin, the results showed that the extraction of EO were carried out mainly in the Northeast (55.5%) and Southeast (19%) regions of Brazil; and the part of the plant most used for the production were the leaves. In addition, the essential oil showed strong antibacterial activity against most of the bacteria tested.(AU)

Lippia sidoides Cham. é amplamente utilizada na medicina popular devido às propriedades antibacterianas atribuídas ao seu óleo essencial (OE). No Brasil, esta planta tem sido introduzida em programas governamentais de fitoterapia, por causa de suas atividades terapêuticas. Isso promoveu um maior interesse na busca por novas moléculas com atividade antimicrobiana presentes neste óleo, as quais foram relatadas por diversos autores. Assim, este trabalho objetivou apresentar um estudo da produção científica da atividade antibacteriana dos compostos químicos do OE da L. sidoide. Para tanto, foram utilizados artigos que abordaram os componentes químicos e atividade antibacteriana por meio de dados de diâmetro de inibição, Concentração Inibitória Mínima (CIM) e Concentração Bactericida Mínima (CBM), publicados entre 2000 e 2020. De um total de 996 estudos identificados, 55 preencheram os critérios de inclusão. Em ordem decrescente, os componentes químicos mais comumente encontrados no OE da L. sidoide foram: timol, p-cimeno e cariofileno. Com relação à origem, os resultados mostraram que a extração do OE foi realizada principalmente nas regiões Nordeste (55,5%) e Sudeste (19%) do Brasil; e a parte da planta mais utilizada para a produção foram as folhas. Além disso, o OE apresentou uma forte atividade antibacteriana contra a maioria das bactérias testadas. (AU)

Effect of Chitosan Addition in Whey-based Biodegradable Films

Abstract Whey, a by-product of dairy industry, is a feedstock widely employed in the production of biodegradable films. However, these films present some limitations when considering the performance of synthetic polymers, especially biological transformation by decomposition. This work aimed to evaluate the effects of chitosan addition to whey-based films to improve films physical-chemical properties and resistance to microbial degradation. The results showed that there was an interaction effect between the chitosan concentration and the storage time for the physical-chemical properties of elongation at break and opacity. There was statistical difference among the formulations; however, for the moisture content and film thickness, there was no interaction effect between the formulation and the storage time. The films with 1.5 and 3.0 wt.% chitosan presented a yellowish hue, characteristic of the polysaccharide; this could also be detected by SEM analysis. The films presented an excellent biodegradability, being decomposed in about 8 days. Considering all chitosan contents tested had similar performances, the chitosan content of 0.15 wt.% was the one with the better cost-benefit relation.

Curcumin Blocks Cytotoxicity of Enteroaggregative and Enteropathogenic Escherichia coli by Blocking Pet and EspC Proteolytic Release From Bacterial Outer Membrane.

Pet and EspC are toxins secreted by enteroaggregative (EAEC) and enteropathogenic (EPEC) diarrheagenic Escherichia coli pathotypes, respectively. Both toxins are members of the Serine Protease Autotransporters of Enterobacteriaceae (SPATEs) family. Pet and EspC are important virulence factors that produce cytotoxic and enterotoxic effects on enterocytes. Here, we evaluated the effect of curcumin, a polyphenolic compound obtained from the rhizomes of Curcuma longa L. (Zingiberaceae) on the secretion and cytotoxic effects of Pet and EspC proteins. We found that curcumin prevents Pet and EspC secretion without affecting bacterial growth or the expression of pet and espC. Our results show that curcumin affects the release of these SPATEs from the translocation domain, thereby affecting the pathogenesis of EAEC and EPEC. Curcumin-treated EAEC and EPEC did not induce significant cell damage like the ability to disrupt the actin cytoskeleton, without affecting their characteristic adherence patterns on epithelial cells. A molecular model of docking predicted that curcumin interacts with the determinant residues Asp1018-Asp1019 and Asp1029-Asp1030 of the translocation domain required for the release of Pet and EspC, respectively. Consequently, curcumin blocks Pet and EspC cytotoxicity on epithelial cells by preventing their release from the outer membrane.

Evaluation of triclosan toxic effects on the methanogenic activity

BACKGROUND: Triclosan (TCS) is an antimicrobial agent widely used in health care and consumer products. This compound is present in sludge of wastewater treatment plants (WWTPs), and because of its bactericidal characteristics, it can inhibit the methanogenic activity in anaerobic digestion (AD) technology. The aim of this study was to evaluate the toxic effects of TCS on the methanogenic activity. RESULTS: Batch anaerobic reactors were used with TCS concentrations of 7.8, 15.7, 23.5, and 31.4 mg/L. These assays consisted in three successive feedings (I, II, and III), wherein the sludge was exposed to each TCS concentration and volatile fatty acid (VFA) substrate. For evaluation of the residual sludge activity during feeding III, only VFA was used. The results showed that the increase in TCS concentrations correlated with the reduction in methane (CH4) production. In this case, the minimum values were achieved for TCS concentration of 31.4 mg/L with CH4 levels between 101.9 and 245.3 during feedings I, II, and III. Regarding the effect of TCS on VFA consumption, an inhibitory effect was detected for TCS concentrations of 23.5 and 31.4 mg/L, with concentrations of acetic, butyric, and propionic acids at the end of the assay (37 d) between 153.6 and 206.8, 62.5 and 60.1, and 93.4 and 110 mg/L, respectively. Regarding the removal of TCS during AD, these values were above 47%. Conclusion: TCS is an inhibitor of methanogenic activity with a decrease between 63 and 70% during the different feedings. The CH4 production was not recovered during feeding III, with inhibition percentages of 21­72%.

Potent and Broad-Spectrum Antimicrobial Activity of Analogs from the Scorpion Peptide Stigmurin.

Scorpion venom constitutes a rich source of biologically active compounds with high potential for therapeutic and biotechnological applications that can be used as prototypes for the design of new drugs. The aim of this study was to characterize the structural conformation, evaluate the antimicrobial activity, and gain insight into the possible action mechanism underlying it, for two new analog peptides of the scorpion peptide Stigmurin, named StigA25 and StigA31. The amino acid substitutions in the native sequence for lysine residues resulted in peptides with higher positive net charge and hydrophobicity, with an increase in the theoretical helical content. StigA25 and StigA31 showed the capacity to modify their structural conformation according to the environment, and were stable to pH and temperature variation-results similar to the native peptide. Both analog peptides demonstrated broad-spectrum antimicrobial activity in vitro, showing an effect superior to that of the native peptide, being non-hemolytic at the biologically active concentrations. Therefore, this study demonstrates the therapeutic potential of the analog peptides from Stigmurin and the promising approach of rational drug design based on scorpion venom peptide to obtain new anti-infective agents.

Potent and broad-spectrum antimicrobial activity of analogs from the scorpion peptide Stigmurin

Scorpion venom constitutes a rich source of biologically active compounds with high potential for therapeutic and biotechnological applications that can be used as prototypes for the design of new drugs. The aim of this study was to characterize the structural conformation, evaluate the antimicrobial activity, and gain insight into the possible action mechanism underlying it, for two new analog peptides of the scorpion peptide Stigmurin, named StigA25 and StigA31. The amino acid substitutions in the native sequence for lysine residues resulted in peptides with higher positive net charge and hydrophobicity, with an increase in the theoretical helical content. StigA25 and StigA31 showed the capacity to modify their structural conformation according to the environment, and were stable to pH and temperature variationresults similar to the native peptide. Both analog peptides demonstrated broad-spectrum antimicrobial activity in vitro, showing an effect superior to that of the native peptide, being non-hemolytic at the biologically active concentrations. Therefore, this study demonstrates the therapeutic potential of the analog peptides from Stigmurin and the promising approach of rational drug design based on scorpion venom peptide to obtain new anti-infective agents.

Bioguided isolation, characterization and media optimization for production of Lysolipins by actinomycete as antimicrobial compound against Xanthomonas citri subsp. citri.

Citrus Canker disease is one of the most important disease in citrus production worldwide caused by gram-negative bacterial pathogen Xanthomonas citri subsp. citri, leading to great economic losses. Currently, a spray of copper-based bactericides is the primary measure for citrus canker management. However, these measures can lead to the contamination of soil by metal contamination, but also the development of copper-resistant Xanthomonas populations. Considering the need to discovery new alternatives to control the citrus canker disease, actinomycetes isolated from the Brazilian Caatinga biome and their crude extracts were tested against different strains of Xanthomonas citri subsp. citri. Streptomyces sp. Caat 1-54 crude extract showed the highest antibiotic activity against Xcc. The crude extract dereplication was performed by LC-MS/MS. Through bioassay-guided fractionation strategy, the antimicrobial activity was assigned to Lysolipins, showing a MIC around 0.4-0.8 µg/mL. Growth media optimization using statistical experimental design increased the Lysolipins production in three-fold production. The preventive and curative effects of the optimized crude extract obtained by experimental design of Caat-1-54 against citrus canker were evaluated in potted 'Pera' sweet orange nursery trees. Caat 1-54 extract was effective in preventing new infections by Xcc on leaves but was not able to reduce Xcc population in pre-established citrus canker lesions. Streptomyces sp. Caat 1-54 extract is a promising, environmentally-friendly source of antimicrobial compound to protect citrus trees against citrus canker.

Efecto antimicrobiano del aceite esencial de Citrus reticulata sobre Fusobacterium nucleatum asociada a enfermedad periodontal / Antimicrobial effect of essential oil of Citrus reticulata on Fusobacterium nucleatum associated with periodontal disease

Resumen La clorhexidina como tratamiento de la enfermedad periodontal ha logrado efectos bactericidas sobre periodontopatógenos y biopelícula oral. Su uso genera efectos adversos, por lo tanto se presentan alternativas naturales con efecto antimicrobiano similar. Los aceites esenciales han demostrado efectividad en el control de la placa dental, sin los efectos adversos de la clorhexidina. El objetivo de este estudio fue determinar el efecto bacteriostático y bactericida del aceite esencial de mandarina contra Fusobacterium nucleatum. Se realizó extracción por expresión del aceite esencial de cáscaras de mandarina (variedades Arrayana y Oneco). Se evaluaron concentraciones al 20%, 40%, 60%, 80% y 100% del aceite esencial diluido en Tween al 0,02%. El efecto bacteriostático y bactericida se determinó por pruebas de sensibilidad antimicrobiana por difusión en disco. Como control positivo se utilizó Clorhexidina 0,2% y agua como control negativo. Se midió halo de inhibición (mm) y se determinó ausencia o presencia de crecimiento bacteriano a partir de unidades formadoras de colonias. Para comparación de proporciones de la actividad bacteriostática y bactericida, se realizó prueba de Fisher y T student (IC 95% p = 0,05). El halo de inhibición a una concentración del 100% mostró comportamiento similar a clorhexidina (p<0,05). Concentraciones al 100% y 80% fueron bactericidas, al 60%, 40% y 20% presentaron comportamiento bacteriostático. No se encontraron diferencias significativas en las proporciones de inhibición entre las dos variedades de mandarina (p>0,05). El uso de aceites esenciales de mandarina podría ser una alternativa complementaria al tratamiento de la enfermedad periodontal.

Abstract Chlorhexidine as a treatment of periodontal disease has achieved bactericidal effects over periodontopathogens and oral biofilm. Its use generates adverse effects; therefore natural alternatives are presented with a similar antimicrobial effect. Essential oils have proved effective in controlling dental plaque without the adverse effects of chlorhexidine. The aim of this study was to determine the bacteriostatic and bactericidal effect of essential oil of tangerine against Fusobacterium nucleatum. The extraction of the essential oil was performed by expression of tangerine peels (Arrayana and Oneco varieties). Concentrations at 20%, 40%, 60%, 80% and 100% of the essential oil diluted in 0,02% Tween were evaluated. The bacteriostatic and bactericidal effect was determined by antimicrobial susceptibility testing by disk diffusion. As a positive control 0,2% chlorhexidine and water as negative control were used. Inhibition zone (mm) was measured and presence or absence of bacterial growth was determined from colony forming units. To compare proportions of bacteriostatic and bactericidal activity, Fisher and T student test (95% CI p = 0,05) were performed. The 100% concentration zone of inhibition showed a similar behavior as chlorhexidine (p <0,05). 100% and 80% concentrations were bactericides, 60%, 40% and 20% showed bacteriostatic behavior. No significant differences between the proportions of inhibition of the two varieties of tangerine (p> 0,05). The use of essential oils of tangerine could be a complementary alternative to treatment of periodontal disease.