1,721,087 research outputs found
A new simple medium for the detection of Enterococcus faecalis and Enterococcus faecium by measurement of conductance changes
No full textA new simple medium for the detection of strains from the Enterococcus species by conductivity measurement was developed and evaluated using the Malthus‐AT system. The analysis repeatability was shown, and the presence of 1 cfu ml‐1 in pure culture was detected within 16 h. The selectivity of the medium was tested using the most common species which are found, in association with microorganisms from the Enterococcus species, in food products and water. Copyright © 1993, Wiley Blackwell. All rights reserve
Microorganisms belonging to the genus enterococcus in foods: Antibiotic resistance and opportunistic pathogenicity
No full textBacteria of the genus Enterococcus, or enterococci (formerly the "faecal" or Lancefield group D streptococci) are ubiquitous microorganisms. Enterococci are predominant inhabitants of the gastrointestinal tract of humans and animals and also commonly occur in large numbers in vegetables, plant material, and foods, especially those of animal origin such as dairy products. Although enterococci share a number of useful biotechnological traits (e.g. bacteriocin production, probiotic characteristics), there is no consensus on the significance of their presence in foodstuffs. The potential pathogenicity of enterococci in human clinical infections and their association with endocarditis have recently become a matter of controversy, in spite of the fact that foods containing enterococci have a long history of safe use. The importance of the enterococci for food and public health microbiologists is related to their enteric habitat, their entering the food chain, their antibiotic resistance, and their possible involvement in food-borne illnesses due to the presence of virulence factors, such as production of adhesins and aggregation substances. More detailed studies are still needed to comprehend the epidemiology, the ecological role, and the virulence of enterococci in foods
Application of the Conductance Measurement Technique for Detection of Streptococcus salivarius ssp. thermophilus Phages
No full textConductance measurement for the detection of Streptococcus salivarius ssp. thermophilus phages was carried out using the Malthus growth analyzer system. Phage activity on a sensitive strain is revealed by a delay in the conductance detection time or a change in the trend of the conductance m e. Analysis of the conductance curve leads to the detection of phage-resistant secondary cultures. The inverse proportion existing between the number of phages and the conductance values recorded at a given time permit evaluation of phage numbers in a sample. Conductance measurement highlights active phages against one of the lactic species present in yogurt. The conductance measurement proved to be an effective alternative to the traditional resazurin method for the detection of S. salivarius ssp. thermophilus phages. The sensitivity of the instrument, time savings, and the ability to analyze a large number of samples simultaneously make the conductance method useful for phage detection. © 1991, American Dairy Science Association. All rights reserved
Analysis of Conductance Changes as a Growth Index of Lactic Acid Bacteria in Milk
No full textThe analysis of changes in conductance is a valid method to evaluate the growth and metabolic activity of lactic acid bacteria in milk. This technique allows the activity of pure strains to be monitored and the stability of the characteristics of mixed cultures to be controlled. The conductimetric method may be particularly useful for the dairy industry to control the stability of lactic acid bacteria starters. © 1993, American Dairy Science Association. All rights reserved
Comparison between impedometry and bioluminescence in the investigation of microorganisms growth
No full textProbiotics and Covid-19
No full textCoronavirus disease 2019 (COVID-19) has become pandemic very rapidly at the beginning of 2020. In the rush to possible therapeutic options, probiotics administration has been proposed mainly based on indirect observation. Some evidence of COVID-19 effects on intestinal microbiota dysbiosis has been shown and probiotics have been considered for their efficacy in the management of respiratory tract viral infections. These observations could be reinforced by the more and more evident existence of a lung-gut axis, suggesting the modulation of gut microbiota among the approaches to the COVID-19 prevention and treatment. As different possible roles of probiotics in this extremely severe illness have been contemplated, the aim of this work is to collect all the currently available information related to this topic, providing a starting point for future studies focussing on it
Selection of Some Bacteriophage and Lysozyme-Resistant Variants of Lactobacillus helveticus CNRZ 892
No full textDifferent strains of Lactobacillus helveticus were tested for lysozyme resistance, and one out of three (L. helveticus CNRZ 892) showed a concomitant resistance to homologous phage 832-B1 (lysozyme-resistant, Φ832-B 1-resistant). The mechanism of phage resistance acquisition seemed to be related to a decreased phage adsorption as well as to a sharp decrease in plaque-forming ability (less than 10–8). Some lysozyme-resistant and Φ832-B1-resistant derivatives of strain CNRZ 892 lost the ability to ferment galactose and trehalose and showed loss and rearrangement of plasmids. Chemical treatments of L. helveticus CNRZ 892 and some phage-resistant derivatives showed that the accessibility of the phage receptor present in the cell wall of some mutants may be masked by a surface component that was absent in the original strain. The results suggested the possibility of using lysozyme as a selective agent to isolate phage-resistant derivatives from a population of L. helveticus CNRZ 892 sensitive to both lysozyme and bacteriophage. © 1992, American Dairy Science Association. All rights reserved
Impedometric analysis applied to food microbiology
No full textGrowth-based impedometric analysis, applied to food microbiology, is a rapid method that enables the indirect tracing of microorganisms by measuring, during time, the changes of electrical conductivity in a matrix in which they grow. This method has been used over the years, to replace the conventional plate count method, to selectively detect the main food-borne diseases and spoilage bacteria. A new metabolic interpretation of the impedance data is the most promising application of this approach. In this review, the advantages of using this technique are discussed, together with the most interesting latest developments that involve the integration with biosensor technology. This method allows the detection of specific bacteria cells, based on their electrical properties, avoiding the culturing step and achieving results in a very short time
Antilisterial Activity by Enterococci in a Model Predicting the Temperature Evolution of Taleggio, an Italian Soft Cheese
No full textEnterococcus ssp. produced broad-spectrum bacteriocins, which were active against Listeria innocua and Listeria monocytogenes. Inhibition of L. innocua in milk by different starter cultures was evaluated. Milk was inoculated with a conventional starter (Streptococcus salivarius ssp. thermophilus and Lactobacillus delbrueckii ssp. bulgaricus mixed cultures) as a sole starter or in combination with inhibitory starter cultures (Enterococcus ssp., bacteriocin-producing strains). Tests were performed under a temperature gradient that reproduced the first 55 h of Taleggio cheese manufacturing and in the presence of rennet. Results indicated that satisfactory inhibition of L. innocua was linked to the combined synergistic antimicrobial effect of pH decrease and bacteriocin production. Overall, data suggested that a potential existed for use of the antagonistic activity from enterococci for protection of Taleggio cheese during ripening, when L. monocytogenes may often reach dangerous concentrations. © 1994, American Dairy Science Association. All rights reserved
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