Potencial bioativo, antioxidante e antimicrobiano do extrato aquoso do processo de extração do óleo essencial de folhas de Croton blanchetianus Baill

O Croton blanchetianus Baill, conhecido como marmeleiro, é rico em metabólitos secundários, como alcalóides e terpenos, que podem apresentar efeitos biológicos. Desta forma, este estudo teve como objetivo avaliar o potencial bioativo, antioxidante e antimicrobiano dos extratos aquosos resultantes do processo de extração do óleo essencial das folhas frescas e secas do C. blanchetianus. O óleo essencial foi extraído por hidrodestilação e posteriormente o extrato aquoso foi coletado e liofilizado, sendo submetido às análises. A determinação da Concentração Inibitória Mínima e Concentração Bactericida Mínima contra bactérias patogênicas de interesse em alimentos (Staphylococcus aureus, Listeria monocytogenes, Salmonella Enteritidis e Escherichia coli) foi realizada pelo método de microdiluição. O efeito dos extratos aquosos sobre as células bacterianas foi avaliado por imagens de microscopia eletrônica de transmissão. A avaliação da atividade antioxidante foi determinada pelo método ABTS e DPPH. O extrato aquoso das folhas frescas apresentou maiores teores de flavonoides e atividade antioxidante por ABTS em comparação com o extrato de folhas secas. Os compostos fenólicos, taninos e a atividade antioxidante pelo método DPPH não diferiram significativamente entre ambos os tipos de folhas. Ambos os extratos aquosos apresentaram atividade antimicrobiana apenas sobre as bactérias Gram-positivas (S. aureus e L. monocytogenes). Foram observadas alterações celulares em S. aureus e L. monocytogenes sob ação do extrato aquoso de folhas frescas e secas. Os resultados indicam a possibilidade de utilização do extrato aquoso das folhas secas de C. blanchetianus como aditivo bioativo e para melhoria da segurança de alimentos, no que diz respeito às bactérias Gram-positivas.

Variations in the Composition, Antioxidant and Antimicrobial Activities of Cystoseira compressa during Seasonal Growth

The underexplored biodiversity of seaweeds has recently drawn great attention from researchers to find the bioactive compounds that might contribute to the growth of the blue economy. In this study, we aimed to explore the effect of seasonal growth (from May to September) on the in vitro antioxidant (FRAP, DPPH, and ORAC) and antimicrobial effects (MIC and MBC) of Cystoseira compressa collected in the Central Adriatic Sea. Algal compounds were analyzed by UPLC-PDA-ESI-QTOF, and TPC and TTC were determined. Fatty acids, among which oleic acid, palmitoleic acid, and palmitic acid were the dominant compounds in samples. The highest TPC, TTC and FRAP were obtained for June extract, 83.4 ± 4.0 mg GAE/g, 8.8 ± 0.8 mg CE/g and 2.7 ± 0.1 mM TE, respectively. The highest ORAC value of 72.1 ± 1.2 µM TE was obtained for the August samples, and all samples showed extremely high free radical scavenging activity and DPPH inhibition (>80%). The MIC and MBC results showed the best antibacterial activity for the June, July and August samples, when sea temperature was the highest, against Listeria monocytogenes, Staphylococcus aureus, and Salmonella enteritidis. The results show C. compressa as a potential species for the industrial production of nutraceuticals or functional food ingredients.

Cymbopogon citratus Essential Oil: Its Application as an Antimicrobial Agent in Food Preservation

Antimicrobial in vitro and in situ efficacies of Cymbopogon citratus essential oil (lemongrass, LGEO) against 17 spoilage microorganisms (bacteria, yeasts and fungi) were evaluated. Additionally, its chemical composition, and antioxidant and antibiofilm activities were investigated. The LGEO exhibited a strong antioxidant activity (84.0 ± 0.1%), and its main constituents were citral (61.5%), geraniol (6.6%) and 1,8-cineole (6.4%). An in vitro antimicrobial evaluation revealed the lowest inhibition zone (1.00 ± 0.00 mm) in Pseudomonas fluorescens, and the highest inhibition zone (18.00 ± 2.46 mm) in Candida krusei. The values for the minimal inhibitory concentration were determined to be the lowest for Salmonella enteritidis and the highest for C. albicans. Furthermore, the concentration of ≥250 µL/L of LGEO suppressed the growth of Penicillium aurantiogriseum, Penicillium expansum, Penicillium chrysogenum and Penicillium italicum. The changes in the molecular structure of the biofilms produced by Pseudomonas fluorescens and Salmonella enteritidis, after their treatment with LGEO, confirmed its action on both biofilm-forming bacteria. Moreover, an in situ antimicrobial activity evaluation displayed the most effective inhibitory effectiveness of LGEO against Micrococcus luteus, Serratia marcescens (250 µL/L) and Penicillium expansum (125, 250 and 500 µL/L) growing on a carrot. Our results suggest that LGEO, as a promising natural antimicrobial agent, can be applied in the innovative packaging of bakery products and different types of vegetables, which combines commonly used packing materials with the addition of LGEO.

The Impact of Pre- and Probiotic Product Combinations on Ex vivo Growth of Avian Pathogenic Escherichia coli and Salmonella Enteritidis

Due to the global spread of antibiotic resistance, there is a strong demand to replace antimicrobial growth promotors in livestock. To identify suitable additives that inhibit the growth of avian pathogenic Escherichia coli O1/O18 and Salmonella enterica serotype Enteritidis strains, an ex vivo screening was performed. Inulin and fructooligosaccharides (FOS) were investigated as prebiotics. Enterococcus faecium and Bacillus coagulans served as probiotic strains. Firstly, the pathogen was anaerobically incubated in caecal digesta from different broiler breeder flocks with the addition of feed additives. Secondly, subsamples of these suspensions were incubated in an antibiotic medium for selective growth of the pathogen. During this step, turbidity was recorded, and lag times were calculated for each pathogen as readout of growth inhibition. Combinations of E. faecium with inulin or FOS significantly extended the lag time for E. coli compared to control. Moreover, older age was a significant factor to enhance this inhibitory effect. In contrast, the combination of FOS and B. coagulans showed shorter lag times for S. Enteritidis. Our results indicate that the E. faecium strain with prebiotics may inhibit the pathogen proliferation in the studied poultry flocks. Furthermore, our results suggest that prophylactic treatments should be assigned by feed additive, age and animal origin.

Investigation of the Potential of Heterophil/Lymphocyte Ratio as a Biomarker to Predict Colonization Resistance and Inflammatory Response to Salmonella enteritidis Infection in Chicken

Salmonella causes significant economic loss to the poultry industry and represents a real threat to human health. The region of difference 21 (ROD21) pathogenicity island removal is a genetic mechanism by which Salmonellaenteritidis (SE) invades the intestinal epithelium and induces systemic infection in mice. The heterophil/lymphocyte (H/L) ratio reflects the chicken’s robustness and immune system status. The H/L ratio is considered a disease resistance trait, and it could be used as a marker for selecting Salmonella resistance in live chickens. However, the association of the H/L ratio with Salmonella resistance and the inflammatory response remains to be elucidated. Moreover, the kinetics of ROD21 excision in the intestine and immune organs of chickens is unknown. Therefore, this study aimed to investigate the bacterial load, the ROD21 excision, the IL-1β, IL-8, and INF-γ blood serum concentration kinetics, and the association with the H/L ratio in chicken at 1, 3, 7, and 21 days post-SE infection. The results showed a significant correlation between the H/L ratio and the bacterial load in the ileum and caecum at 7 dpi. The ROD21 pathogenicity island absolute and relative excision in the caecum were positively correlated at 1 dpi but negatively correlated at 7 dpi with the H/L ratio. However, in the liver, we found the opposite tendency. The association of the H/L ratio with IL-1β, IL-8, and INF-γ blood serum concentrations showed that a low H/L ratio is correlated with increased IL-1β and INF-γ at 21 dpi. This study confirmed that the H/L ratio is associated with robustness and Salmonella-resistance in chicken. The methodology used in this study can separate individuals into susceptible and resistant and can help in the selection and breeding of Salmonella-resistant chickens.

Virulence Gene Profile, Antimicrobial Resistance and Multilocus Sequence Typing of Salmonella enterica Subsp. enterica Serovar Enteritidis from Chickens and Chicken Products

This study was undertaken to determine the virulence, antimicrobial resistance and molecular subtypes of Salmonella in the Central Region of Peninsular Malaysia. A total of 45 Salmonella Enteritidis were detected from live chicken (cloacal swab), and chicken products (fresh and ready-to-eat meat) samples upon cultural isolation and serotyping. Similarly, an antimicrobial susceptibility test based on the Kirby Bauer disk diffusion method as well as antimicrobial resistance AMR genes, virulence determinants and multilocus sequence typing (MLST) typing were conducted after the Whole Genome Sequencing and analysis of the isolates. The results indicate that sequence types ST1925 (63.7%), and ST11 (26.5%) were the predominant out of the seven sequence types identified (ST292, ST329, ST365, ST423 and ST2132). The phenotypic antimicrobial profile corresponds to the genotypic characterization in that the majority of the isolates that exhibited tetracycline, gentamycin and aminoglycoside resistance; they also possessed the tetC and blaTEM β-Lactam resistance genes. However, isolates from cloacal swabs showed the highest number of resistance genes compared to the chicken products (fresh and ready-to-eat meat) samples. Furthermore, most of the virulence genes were found to cluster in the Salmonella pathogenicity island (SPI). In this study, all the isolates were found to possess SPI-1, which codes for the type III secretion system, which functions as actin-binding proteins (SptP and SopE). The virulence plasmid (VP) genes (spvB, spvC) were present in all genotypes except ST365. The findings of this study, particularly with regard to the molecular subtypes and AMR profiles of the Salmonella Enteritidis serotype shows multidrug-resistance features as well as genetic characteristics indicative of high pathogenicity.

Cellulose Acetate Membranes Modification by Aminosilane Grafting in Supercritical Carbon Dioxide towards Antibiofilm Properties

The study explores the grafting of cellulose acetate microfiltration membranes with an aminosilane to attain antibiofilm properties. The grafting reaction was performed in the supercritical carbon dioxide used as a transport and reaction medium. The FTIR analyses and dissolution tests confirmed the covalent bonding between the aminosilane and polymer. The membranes’ microstructure was investigated using a dual-beam SEM and ion microscopy, and no adverse effects of the processing were found. The modified membranes showed a more hydrophilic nature and larger water permeate flow rate than the neat cellulose acetate membranes. The tests in a cross-filtration unit showed that modified membranes were considerably less blocked after a week of exposure to Staphylococcus aureus and Escherichia coli than the original ones. Microbiological investigations revealed strong antibiofilm properties of the grafted membranes in experiments with Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella Enteritidis.