Metabolomics-Based Screening of Biofilm-Inhibitory Compounds against Pseudomonas aeruginosa from Burdock Leaf

Screening of anti-biofilm compounds from the burdock leaf based on metabolomics is reported here. The crystal violet assay indicated 34% ethanol elution fraction of burdock leaf could completely inhibit biofilm formation of Pseudomonas aeruginosa at 1 mg·mL−1. Then, the chemical composition of burdock leaf fraction was analyzed by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) and 11 active compounds (chlorogenic acid, caffeic acid, p-coumaric acid, quercetin, ursolic acid, rutin, cynarin, luteolin, crocin, benzoic acid, and Tenacissoside I) were identified. Lastly, UPLC-MS analysis was employed to obtain the metabolic fingerprints of burdock leaf fractions before and after inhibiting the biofilm of Pseudomonas aeruginosa. The metabolic fingerprints were transformed to data, analyzed with PLS-DA (partial least squares discriminant analysis) and the peaks whose area was significantly changed were found out. Thus, 81 compounds were screened as potential anti-biofilm ingredients. Among them, rutin, ursolic acid, caffeic acid, p-coumaric acid and quercetin were identified and confirmed as the main anti-biofilm compounds in burdock leaf. The study provided basic anti-biofilm profile data for the compounds in burdock leaf, as well as provided a convenient method for fast screening of anti-biofilm compounds from natural plants

Anti-quorum sensing and anti-biofilm activity of Amomum tsaoko (Amommum tsao-ko Crevost et Lemarie) on foodborne pathogens

Cell-to-cell communication or quorum sensing (QS) leads to biofilm formation and causing other virulence factors which are extreme problems for food safety, biofilm related infectious diseases etc. This study evaluated the anti-QS activity of the Amomum tsaoko extract (0.5–4 mg/ml) by using Chromobacterium violaceum a biosensor strain and biofilm formation by crystal violate assay. Experimental results demonstrated that the overall yield of Amomum tsao-ko extract was 11.33 ± 0.3% (w/w). MIC for Staphylococcus aureus (Gram positive), Salmonella Typhimurium and Pseudomonas aeruginosa (Gram negative) was 1, 2 and 2 mg/ml, respectively. A concentration of 4 mg/ml extract showed highest biofilm inhibition 51.96% on S. Typhimurium when 47.06%, 45.28% were shown by S. aureus, P. aeruginosa respectively. The damage of biofilm architecture was observed by Confocal Laser Scanning Microscopy (CLSM). A level of 44.59% inhibition of violacein production was demonstrated when the dose was 4 mg/ml. Swarming motility inhibition was observed in a dose dependent manner. Taken together, the treatment of A. tsaoko extract can deliver value to food product and medicine by controlling pathogenesis

Aptamer Immobilized Magnetoelastic Sensor for the Determination of <i>Staphylococcus aureus</i>

<div><p>An aptamer-based magnetoelastic sensor for the determination of Staphylococcus aureus is reported. Aptamers specific to S. aureus were used to ensure specific and selective binding of bacteria on the sensor surface. The sensors were exposed to <i>S. aureus</i> concentrations of 1 × 10¹–1 × 10¹¹ colony forming units per milliliter, and the changes in resonance frequency were monitored. The sensitivity was higher for sensors with smaller physical dimensions. The biosensor with dimensions of 2 × 5 × 0.028 millimeters provided a linear dynamic range of 10¹–10¹¹ colony forming units per milliliter and a detection limit of 5 colony forming units per milliliter. The results also demonstrated that the magnetoelastic sensors determined the targeted pathogenic species with good selectivity. The method was employed to determine <i>S. aureus</i> in water, and the results were comparable to those obtained by plate-counting methods. The high sensitivity, selectivity, and stability of the aptamer provide a promising approach for the determination of pathogenic bacteria.</p></div

Advancements and application of immunosensors in the analysis of food contaminants

Azam MS, Rahman MRT, Lou Z, Tang Y, Raqib SM, Jothi JS. 2014. Advancements and application of immunosensors in the analysis of food contaminants. Nusantara Bioscience 6: 186-195. Immunosensors are affinity ligand-based biosensor solid-state devices in which the immunochemical reaction is coupled to a transducer. The fundamental basis of all immunosensors is the specificity of the molecular recognition of antigens by antibodies to form a stable complex. This is similar to the immunoassay methodology. Immunosensors can be categorized based on the detection principle applied. The main developments are electrochemical, optical, and microgravimetric immunosensors. In contrast to immunoassay, modern transducer technology enables the label-free detection and quantification of the immune complex. The analysis of trace substances in environmental science, pharmaceutical and food industries is a challenge since many of these applications demand a continuous monitoring mode. The use of immunosensors in these applications is most appropriate. Food chemists should take advantage of immunosensors in food and clinical diagnostics. There are many recent developments in the immunosensor field which have potential impacts. The future role of this technique in intra-laboratory, as well as bedside testing, will become even more important as the food laboratory is faced with increasing pressure to contain costs. Objective of this paper is to give a general overview of the possible application of immunosensors to the food analysis field

Determination of preservative residues and microbial contents of commercial Chinese duck neck meat

Los productos cárnicos de cuello de pato son aperitivos tradicionales y populares en China por su atractivo sabor picante, aroma y textura. Estos productos son muy perecederos y se utilizan diferentes tipos de conservantes químicos de forma extensiva. Este estudio determinó los niveles de conservantes y la carga microbiana en productos cárnicos de cuello de pato chino mediante cromatografía de gas y métodos de placa de agar, respectivamente. Los resultados mostraron que los productos cárnicos de cuello de pato chino contienen metil p-hidroxibenzoato (E-218) en un rango de 21,15 μg/g – 14,5 mg/g, ácido propiónico (E-280) en un rango de 26,84 – 30,24 mg/g y ácido benzoico (E-210) en un rango no detectado – 15,99 μg/g. No se detectó ácido sórbico (E-200). El recuento total por placa fue de 1,01 – 2,03 log cfu/g y los recuentos de Lactobacillus fueron de 1,04 – 1,43 log cfu/g. El cuello de pato crudo refrigerado contenía todos los microorganismos examinados, mientras que no se detectaron levadura, moho ni salmonella en ninguno de los productos cárnicos de cuello de pato procesados.Duck neck meat products are traditional, popular snack items in China for its attractive spicy taste, flavor and texture. These products are perishable and different types of chemical preservatives are used extensively. This study determined the levels of preservatives and microbial load in Chinese duck neck meat product by gas chromatography and agar plate methods, respectively. The results showed that Chinese duck neck meat product contains methyl-p-hydroxybenzoate (E-218) in the range 21.15 μg/g–14.5 mg/g, propionic acid (E-280) in the range 26.84–30.24 mg/g and benzoic acid (E-210) in the range not detected – 15.99 μg/g. Sorbic acid (E-200) was not detected. The total plate counts were 1.01–2.03 log cfu/g, and Lactobacilli counts were 1.04–1.43 log cfu/g. Refrigerated raw duck neck contained all the tested microorganisms while yeast, mold and salmonella were not detected in all of the processed duck neck meat products