Application of EvaGreen for the assessment of Listeria monocytogenes АТСС 13932 cell viability using flow cytometry

Effect of Molecular Weight of Fluorescent Dyes on DNA Separation by Capillary Electrophoresis

Capillary electrophoresis (CE) plays an important role in the quality control of dsDNA. So far, there has been various fluorescent dyes employed for the separation of dsDNA by CE. However, the molecular weight of the dyes may affect the mass to charge ratio of dsDNA-dye complex, consequently the separation performance of dsDNA will be changed. Herein, we systematically compared the fluorescent intensity and migration times when separating the dsDNA fragments labeled or intercalated by different dyes. Results showed that the concentration of SYBR Green I affected the migration times more than Gel Green and EvaGreen, which may be caused by the lower molecular weight of EvaGreen. The optimal concentration for SYBR Green I and Gel Green is 1×, and it is 0.005× for EvaGreen. There is linear relationship between dsDNA concentration (0.1-0.5 ng/µL) and fluorescence intensity when using SYBR Green I or Gel Green for separation. Finally, we have resolved the фX174-Hinc II digest in 0.5% HEC (1300k) containing 1× SYBR within 12 min, even though there is only 6 bp difference for the adjacent dsDNA fragments. Furthermore, we also obtained the virtual dsDNA bands by OpenCV according to the electropherogram.

Cytokine Profile Response of Human Peripheral Blood Mononuclear Cells Stimulated by Bartonella bacilliformis

Carrion's disease is a neglected endemic disease found in remote Andean areas. As an overlooked disease, knowledge of innate immune responses to Bartonella bacilliformis, the etiological agent, is scarce. This study aimed to evaluate the cytokine response to B. bacilliformis using in vitro human peripheral blood mononuclear cells (PBMCs) stimulations. PBMCs from naive adults were isolated by gradient centrifugation and cocultured with heat-inactivated (HI) B. bacilliformis at different incubation times (3, 6, 12, 24, and 36 h). Cytokines, chemokines, and growth factors were determined in culture supernatants by multiplex fluorescent bead-based quantitative suspension array technology. During the first 36 h, a proinflammatory response was observed, including tumor necrosis factor-α, interleukin (IL)-1α, IL-1β, interferon-α2, and IL-6, followed by an anti-inflammatory response mainly related to IL-1RA. Moreover, high expression levels of chemokines IL-8, monocyte chemoattractant protein-1α, and macrophage inflammatory protein (MIP)-1β were detected from 3 h poststimulation and MIP-1α was detected at 24 h. Some growth factors, mainly granulocyte macrophage colony-stimulating factor and granulocyte colony-stimulating factor, and in minor concentrations vascular endothelial growth factor, epidermal growth factor, and eotaxin, were also detected. Innate response to HI B. bacilliformis stimulation consists of a rapid and strong proinflammatory response characterized by a wide range of cytokines and chemokines followed by an anti-inflammatory response and increased specific growth factors.

Potential of Flow Cytometric Approaches for Rapid Microbial Detection and Characterization in the Food Industry-A Review

As microbial contamination is persistent within the food and bioindustries and foodborne infections are still a significant cause of death, the detection, monitoring, and characterization of pathogens and spoilage microorganisms are of great importance. However, the current methods do not meet all relevant criteria. They either show (i) inadequate sensitivity, rapidity, and effectiveness; (ii) a high workload and time requirement; or (iii) difficulties in differentiating between viable and non-viable cells. Flow cytometry (FCM) represents an approach to overcome such limitations. Thus, this comprehensive literature review focuses on the potential of FCM and fluorescence in situ hybridization (FISH) for food and bioindustry applications. First, the principles of FCM and FISH and basic staining methods are discussed, and critical areas for microbial contamination, including abiotic and biotic surfaces, water, and air, are characterized. State-of-the-art non-specific FCM and specific FISH approaches are described, and their limitations are highlighted. One such limitation is the use of toxic and mutagenic fluorochromes and probes. Alternative staining and hybridization approaches are presented, along with other strategies to overcome the current challenges. Further research needs are outlined in order to make FCM and FISH even more suitable monitoring and detection tools for food quality and safety and environmental and clinical approaches.

Flow cytometry as a rapid test for detection of tetracycline resistance directly in bacterial cells in Micrococcus luteus

Correct effective doses of antibiotics are important in the treatment of infectious diseases. The most frequently used methods for determination of the antibiotic susceptibility of bacterial pathogens are slow. The detection of multidrug-resistant bacteria currently relies on primary isolation followed by phenotypic detection of antibiotic resistance by measuring bacterial growth in the presence of the antibiotic being tested. The basic requirements for methods of detection of resistance to antibiotics include speed and accuracy. We studied the speed and accuracy of flow cytometry for the detection of tetracycline resistance in the Gram-positive bacteria Micrococcus luteus. Detection of cell viability and reliability of antibiotic resistance was carried out on the Guava EasyCyte flow cytometer (Merck Millipore, Germany) with SYBR Green and PI dyes. M. luteus was exposed to tetracycline (at 30, 90, 180 and 270 μg.mL-1) over 24 hours. Concentrations of live and dead cells were measured after 4 and 24 hours of incubation. The results revealed that the use of mixed dyes PI and SYBR Green allowed the division of cells into large subpopulations of live and dead cells and the DNA of destroyed cells. After 4 h exposure to tetracycline 30 μg.mL-1, the subpopulation of live cells decreased by 47% compared to the positive control. Tetracycline at 90 μg.mL-1 decreased the subpopulation of live cells by 59% compared to the positive control. A continued increase in concentration caused a shift in the population and an increase in dead cells, indicating damage to the cells of the microorganism. Incubation of M. luteus with 180 and 270 μg.mL-1 tetracycline decreased the subpopulation of live cells by 82% and 94%, respectively, in comparison with the positive control. After incubation with 30 μg of tetracycline over 24 h the number of living cells decreased by 70% in comparison with the positive control. Tetracycline treatment (90 μg.mL-1 for 24 h) killed 71% of cells. After exposure to 90 μg.mL-1 tetracycline 29% cells were viable. The viability of living cells was confirmed by a microbiological test.

Assessment of antimicrobial potential of substances isolated from some wastes of meat processing industry

The slaughter of farm animals generates a large number of by-products. Meat waste management includes various methods, but cost-effective technologies are still in priority. This manuscript reports the results of the study of antimicrobial activity of substances isolated from such wastes of meat processing industry as bovine and pork mucous membranes and epithelial tissues. Proteomic study included two-dimensional electrophoresis with following mass spectrometric identification. Antimicrobial activity against L. monocytogenes, P. aeruginosa and S. aureus of neutralized native extracts and after enzymatic treatment as well as its ultrafiltrates was determined by flow cytometry with EvaGreen and PI dyes. It was shown that a large number of histones were found in bovine mucous membranes as well as several tissue-specific proteins, which would be a precursor of bioactive peptides. Bovine mucous membranes of the tongue and nasal cavity possessed the greatest activity in relation to P. aeruginosa, the rate of surviving cells decreased to 22.0%. Bovine mucous membranes of the rectum and the oral cavity, submandibular lymph nodes, pig mucous membranes of the larynx, tongue, lips, and rectum increased dead cells count up to 40% of all cells. Bovine nasal mucosa and pork mucous of labial cavity possessed the greatest activity against S. aureus, the rate of surviving cells did not exceed 10.0%. Determination of antimicrobial action against L. monocytogenes of native samples and treated with trypsin showed that bovine mucous membranes of the rectum and oral cavity, pork mucosa of the lips and submandibular glands were the most active. Treatment with trypsin or ultrafiltration demonstrated different effects on activity of samples. It was shown the perspectivity of recycling of such type of by-products into effective and demanded substances which can be used, for example, in the food industry as an alternative to chemical preservatives.