The Experts below are selected from a list of 192 Experts worldwide ranked by ideXlab platform

Per Einar Granum - One of the best experts on this subject based on the ideXlab platform.

  • Rapid discrimination of cytK-1 and cytK-2 genes in Bacillus cereus strains by a novel duplex PCR system
    FEMS Microbiology Letters, 2006
    Co-Authors: Marie Helene Guinebretière, Per Einar Granum, Annette Fagerlund, Christophe Nguyen-the
    Abstract:

    Bacillus cereus is the causative agent of gastrointestinal diarrhoea. At least three known Enterotoxins may be involved in this syndrome: nonhaemolytic (Nhe) Enterotoxin, Hbl Enterotoxin and cytotoxin K. Two different forms were recently described for cytotoxin K, encoded by cytK-1 and cytK-2 genes. The CytK-1 toxin appeared to carry a high toxicity, but there is currently no method available to rapidly detect and discriminate the B. cereus strains able to produce this CytK-1 form. In this study, a duplex PCR assay was developed and validated on 162 known cytotoxin-containing strains. This PCR method is the first molecular tool to provide rapid detection and discrimination of cytK-1- and cytK-2-carrying B. cereus strains.

  • bacillus cereus and its food poisoning toxins
    Fems Microbiology Letters, 1997
    Co-Authors: Per Einar Granum, Terje Lund
    Abstract:

    Bacillus cereus is becoming one of the more important causes of food poisoning in the industrialised world. It produces one emetic toxin and three different Enterotoxins. The emetic toxin is a ring-shaped structure of three repeats of four amino and/or oxy acids: [d-O-Leu-d-Ala-l-O-Val-l-Val]3. This ring structure has a molecular mass of 1.2 kDa, and is chemically closely related to the potassium ionophore valinomycin. Two of the three Enterotoxins have been shown to be involved in food poisoning. They both consist of three different proteins that act together. One of these Enterotoxins is also a haemolysin. This haemolytic Enterotoxin is transcribed from one operon. The third Enterotoxin is a single component protein, but has not been shown to be involved in food poisoning.

  • characterisation of a non haemolytic Enterotoxin complex from bacillus cereus isolated after a foodborne outbreak
    Fems Microbiology Letters, 1996
    Co-Authors: Terje Lund, Per Einar Granum
    Abstract:

    Three enterotoxic components have been isolated from a strain of Bacillus cereus which was involved in a large food poisoning outbreak in Norway in 1995. The components were purified by chromatography on three different columns. Three proteins of 39, 45 and 105 kDa, respectively, were found to be necessary for maximum cytotoxicity. The amino acid N-terminal sequences of the 39 and 45 kDa proteins were determined. The 45 kDa component was the same protein as the main antigen detected in the Bacillus Diarrhoeal Enterotoxin Visual Immunoassay (Tecra). The 39 kDa protein showed some similarity to the l1 protein of haemolysin BL from B. cereus. Furthermore, the three toxic components were all recognised by a polyclonal antiserum reported to detect Enterotoxin from B. cereus. The proteins were different from the B- and L2-components of haemolysin BL, previously suggested to be a primary virulence factor, and had no detectable haemolytic activity.

Terje Lund - One of the best experts on this subject based on the ideXlab platform.

  • bacillus cereus and its food poisoning toxins
    Fems Microbiology Letters, 1997
    Co-Authors: Per Einar Granum, Terje Lund
    Abstract:

    Bacillus cereus is becoming one of the more important causes of food poisoning in the industrialised world. It produces one emetic toxin and three different Enterotoxins. The emetic toxin is a ring-shaped structure of three repeats of four amino and/or oxy acids: [d-O-Leu-d-Ala-l-O-Val-l-Val]3. This ring structure has a molecular mass of 1.2 kDa, and is chemically closely related to the potassium ionophore valinomycin. Two of the three Enterotoxins have been shown to be involved in food poisoning. They both consist of three different proteins that act together. One of these Enterotoxins is also a haemolysin. This haemolytic Enterotoxin is transcribed from one operon. The third Enterotoxin is a single component protein, but has not been shown to be involved in food poisoning.

  • characterisation of a non haemolytic Enterotoxin complex from bacillus cereus isolated after a foodborne outbreak
    Fems Microbiology Letters, 1996
    Co-Authors: Terje Lund, Per Einar Granum
    Abstract:

    Three enterotoxic components have been isolated from a strain of Bacillus cereus which was involved in a large food poisoning outbreak in Norway in 1995. The components were purified by chromatography on three different columns. Three proteins of 39, 45 and 105 kDa, respectively, were found to be necessary for maximum cytotoxicity. The amino acid N-terminal sequences of the 39 and 45 kDa proteins were determined. The 45 kDa component was the same protein as the main antigen detected in the Bacillus Diarrhoeal Enterotoxin Visual Immunoassay (Tecra). The 39 kDa protein showed some similarity to the l1 protein of haemolysin BL from B. cereus. Furthermore, the three toxic components were all recognised by a polyclonal antiserum reported to detect Enterotoxin from B. cereus. The proteins were different from the B- and L2-components of haemolysin BL, previously suggested to be a primary virulence factor, and had no detectable haemolytic activity.

Sophia Johler - One of the best experts on this subject based on the ideXlab platform.

  • the role of regulatory mechanisms and environmental parameters in staphylococcal food poisoning and resulting challenges to risk assessment
    Frontiers in Microbiology, 2019
    Co-Authors: Nikoleta Zeaki, Sophia Johler, Panagiotis N Skandamis, Jenny Schelin
    Abstract:

    Prevention, prediction, control, and handling of bacterial foodborne diseases - an ongoing, serious, and costly concern worldwide - are continually facing a wide array of difficulties. Not the least due to that food matrices, highly variable and complex, can impact virulence expression in diverse and unpredictable ways. This review aims to present a comprehensive overview of challenges related to the presence of enterotoxigenic Staphylococcus aureus in the food production chain. It focuses on characteristics, expression, and regulation of the highly stable staphylococcal Enterotoxins and in particular staphylococcal Enterotoxin A (SEA). Together with the robustness of the pathogen under diverse environmental conditions and the range of possible entry routes into the food chain, this poses some of the biggest challenges in the control of SFP. Furthermore, the emergence of new Enterotoxins, found to be connected with SFP, brings new questions around their regulatory mechanisms and expression in different food environments. The appearance of increasing amounts of antibiotic resistant strains found in food is also highlighted. Finally, potentials and limitations of implementing existing risk assessment models are discussed. Various quantitative microbial risk assessment approaches have attempted to quantify the growth of the bacterium and production of disease causing levels of toxin under various food chain and domestic food handling scenarios. This requires employment of predictive modeling tools, quantifying the spatiotemporal population dynamics of S. aureus in response to intrinsic and extrinsic food properties. In this context, the armory of predictive modeling employs both kinetic and probabilistic models to estimate the levels that potentiate toxin production, the time needed to reach that levels, and overall, the likelihood of toxin production. Following risk assessment, the main challenge to mitigate the risk of S. aureus intoxication is first to prevent growth of the organism and then to hamper the production of Enterotoxins, or at least prevent the accumulation of high levels (e.g., >10-20 ng) in food. The necessity for continued studies indeed becomes apparent based on the challenges to understand, control, and predict Enterotoxin production in relation to the food environment. Different types of food, preservatives, processing, and packaging conditions; regulatory networks; and different staphylococcal Enterotoxin-producing S. aureus strains need to be further explored to obtain more complete knowledge about the virulence of this intriguing pathogen.

  • Enterotoxin production of bacillus thuringiensis isolates from biopesticides foods and outbreaks
    Frontiers in Microbiology, 2018
    Co-Authors: Sophia Johler, Eva Maria Kalbhenn, Nicole Heini, Peter Brodmann, Sylvia Gautsch, Murat Bagcioglu, Matthias Contzen, Roger Stephan, Monika Ehlingschulz
    Abstract:

    While the relevance of Bacillus (B.) cereus as a major cause of gastroenteritis is undisputed, the role of the closely related B. thuringiensis in foodborne disease is unclear. B. thuringiensis strains frequently harbor Enterotoxin genes. However, the organism has only very rarely been associated with foodborne outbreaks, possibly due to the fact that during outbreak investigations, B. cereus is routinely not differentiated from B. thuringiensis. A recent EFSA scientific opinion stresses the urgent need for further data allowing for improved risk assessment, in particular as B. thuringiensis is a commonly used biopesticide. Therefore, the aim of this study was to gain further insights into the hazardous potential of B. thuringiensis. To this end, 39 B. thuringiensis isolates obtained from commercially used biopesticides, various food sources, as well as from foodborne outbreaks were characterized by panC typing, panC-based SplitsTree analysis, toxin gene profiling, FTIR spectroscopic analysis, a cytotoxicity assay screening for enterotoxic activity, and a sphingomyelinase assay. The majority of the tested B. thuringiensis isolates exhibited low (23%, n = 9) or mid level enterotoxicity (74%, n = 29), and produced either no (59%, n = 23) or low levels (33%, n = 13) of sphingomyelinase, which is reported to act synergistically with Enterotoxins Nhe and Hbl. One strain isolated from rosemary was however classified as highly enterotoxic surpassing the cytotoxic activity of the high-level reference strain by a factor of 1.5. This strain also produced vast amounts of sphingomyelinase. Combining all results obtained in this study into a fingerprint pattern, several enterotoxic biopesticide strains were indistinguishable from those of isolates from foods or collected in association with outbreaks. Our study shows that many B. thuringiensis biopesticide strains exhibit mid-level cytotoxicity in a Vero cell assay and that some of these strains cannot be differentiated from isolates collected from foods or in association with outbreaks. Thus, we demonstrate that the use of B. thuringiensis strains as biopesticides can represent a food safety risk, underpinning the importance of assessing the hazardous potential of each strain and formulation used.

Jenny Schelin - One of the best experts on this subject based on the ideXlab platform.

  • the role of regulatory mechanisms and environmental parameters in staphylococcal food poisoning and resulting challenges to risk assessment
    Frontiers in Microbiology, 2019
    Co-Authors: Nikoleta Zeaki, Sophia Johler, Panagiotis N Skandamis, Jenny Schelin
    Abstract:

    Prevention, prediction, control, and handling of bacterial foodborne diseases - an ongoing, serious, and costly concern worldwide - are continually facing a wide array of difficulties. Not the least due to that food matrices, highly variable and complex, can impact virulence expression in diverse and unpredictable ways. This review aims to present a comprehensive overview of challenges related to the presence of enterotoxigenic Staphylococcus aureus in the food production chain. It focuses on characteristics, expression, and regulation of the highly stable staphylococcal Enterotoxins and in particular staphylococcal Enterotoxin A (SEA). Together with the robustness of the pathogen under diverse environmental conditions and the range of possible entry routes into the food chain, this poses some of the biggest challenges in the control of SFP. Furthermore, the emergence of new Enterotoxins, found to be connected with SFP, brings new questions around their regulatory mechanisms and expression in different food environments. The appearance of increasing amounts of antibiotic resistant strains found in food is also highlighted. Finally, potentials and limitations of implementing existing risk assessment models are discussed. Various quantitative microbial risk assessment approaches have attempted to quantify the growth of the bacterium and production of disease causing levels of toxin under various food chain and domestic food handling scenarios. This requires employment of predictive modeling tools, quantifying the spatiotemporal population dynamics of S. aureus in response to intrinsic and extrinsic food properties. In this context, the armory of predictive modeling employs both kinetic and probabilistic models to estimate the levels that potentiate toxin production, the time needed to reach that levels, and overall, the likelihood of toxin production. Following risk assessment, the main challenge to mitigate the risk of S. aureus intoxication is first to prevent growth of the organism and then to hamper the production of Enterotoxins, or at least prevent the accumulation of high levels (e.g., >10-20 ng) in food. The necessity for continued studies indeed becomes apparent based on the challenges to understand, control, and predict Enterotoxin production in relation to the food environment. Different types of food, preservatives, processing, and packaging conditions; regulatory networks; and different staphylococcal Enterotoxin-producing S. aureus strains need to be further explored to obtain more complete knowledge about the virulence of this intriguing pathogen.

  • the formation of staphylococcus aureus Enterotoxin in food environments and advances in risk assessment
    Virulence, 2011
    Co-Authors: Jenny Schelin, Nina Wallincarlquist, Marianne Thorup Cohn, Roland Lindqvist, G C Barker, Peter Radstrom
    Abstract:

    The recent finding that the formation of staphylococcal Enterotoxins in food is very different from that in cultures of pure Staphylococcus aureus sheds new light on, and brings into question, traditional microbial risk assessment methods based on planktonic liquid cultures. In fact, most bacteria in food appear to be associated with surfaces or tissues in various ways, and interaction with other bacteria through molecular signaling is prevalent. Nowadays it is well established that there are significant differences in the behavior of bacteria in the planktonic state and immobilized bacteria found in multicellular communities. Thus, in order to improve the production of high-quality, microbiologically safe food for human consumption, in situ data on Enterotoxin formation in food environments are required to complement existing knowledge on the growth and survivability of S. aureus. This review focuses on enterotoxigenic S. aureus and describes recent findings related to Enterotoxin formation in food environments, and ways in which risk assessment can take into account virulence behavior. An improved understanding of how environmental factors affect the expression of Enterotoxins in foods will enable us to formulate new strategies for improved food safety.

Elizabeth B. Norton - One of the best experts on this subject based on the ideXlab platform.

  • the mucosal vaccine adjuvant lt r192g l211a or dmlt
    mSphere, 2018
    Co-Authors: John D. Clements, Elizabeth B. Norton
    Abstract:

    ABSTRACT Perhaps the best-studied mucosal adjuvants are the bacterially derived ADP-ribosylating Enterotoxins. This adjuvant family includes heat-labile Enterotoxin of Escherichia coli (LT), cholera toxin (CT), and mutants or subunits of LT and CT. These proteins promote a multifaceted antigen-specific response, including inflammatory Th1, Th2, Th17, cytotoxic T lymphocytes (CTLs), and antibodies. However, more uniquely among adjuvant classes, they induce antigen-specific IgA antibodies and long-lasting memory to coadministered antigens when delivered mucosally or even parenterally. The purpose of this minireview is to describe the general properties, history and creation, preclinical studies, clinical studies, mechanisms of action, and considerations for use of the most promising Enterotoxin-based adjuvant to date, LT(R192G/L211A) or dmLT. This review is timely due to completed, ongoing, and planned clinical investigations of dmLT in multiple vaccine formulations by government, nonprofit, and industry groups in the United States and abroad.

  • The Mucosal Vaccine Adjuvant LT(R192G/L211A) or dmLT
    American Society for Microbiology, 2018
    Co-Authors: John D. Clements, Elizabeth B. Norton
    Abstract:

    Perhaps the best-studied mucosal adjuvants are the bacterially derived ADP-ribosylating Enterotoxins. This adjuvant family includes heat-labile Enterotoxin of Escherichia coli (LT), cholera toxin (CT), and mutants or subunits of LT and CT.Perhaps the best-studied mucosal adjuvants are the bacterially derived ADP-ribosylating Enterotoxins. This adjuvant family includes heat-labile Enterotoxin of Escherichia coli (LT), cholera toxin (CT), and mutants or subunits of LT and CT. These proteins promote a multifaceted antigen-specific response, including inflammatory Th1, Th2, Th17, cytotoxic T lymphocytes (CTLs), and antibodies. However, more uniquely among adjuvant classes, they induce antigen-specific IgA antibodies and long-lasting memory to coadministered antigens when delivered mucosally or even parenterally. The purpose of this minireview is to describe the general properties, history and creation, preclinical studies, clinical studies, mechanisms of action, and considerations for use of the most promising Enterotoxin-based adjuvant to date, LT(R192G/L211A) or dmLT. This review is timely due to completed, ongoing, and planned clinical investigations of dmLT in multiple vaccine formulations by government, nonprofit, and industry groups in the United States and abroad