Peter Raspor

Effects of natural antimicrobials on bacterial cell hydrophobicity, adhesion, and zeta potential

Abstract Interactions between bacterial cells and contact materials play an important role in food safety and technology. As bacterial strains become ever more resistant to antibiotics, the aim of this study was to analyse adhesion of selected foodborne bacterial strains on polystyrene surface and to evaluate the effects of natural antimicrobials on bacterial cell hydrophobicity, adhesion, and zeta potential as strategies of adhesion prevention. The results showed strain-specific adhesion rate on polystyrene. The lowest and the highest adhesion were found for two B. cereus lines. Natural antimicrobials ferulic and rosmarinic acid substantially decreased adhesion, whereas the effect of epigallocatechin gallate was neglectful. Similar results were found for the zeta potential, indicating that natural antimicrobials reduce bacterial adhesion. Targeting bacterial adhesion using natural extracts we can eliminate potential infection at an early stage. Future experimental studies should focus on situations that are as close to industrial conditions as possible.

Attenuation of Adhesion, Biofilm Formation and Quorum Sensing of Campylobacter jejuni by Euodia ruticarpa

Thermophilic campylobacters are a major cause of bacterial food‐borne diarrhoeal disease. Adherence and biofilm formation are key elements of Campylobacter jejuni persistence in unfavourable environmental conditions. The phytochemical analysis of Euodia ruticarpa fruit ethanol solution extract (EREE) indicated that the major compounds were evodiamine (1), rutaecarpine (2) and evocarpine (9). E. ruticarpa fruit ethanol solution extract, compounds 1 and 2 as well as a mixture of quinolinone alkaloids with 41.7% of 9 were tested for antibacterial, antibiofilm and antiquorum sensing activities against C. jejuni. Minimal inhibitory concentrations varied from 64 to 1024 µg/mL. A mutant strain that lacks the functional gene coding for the CmeB efflux pump protein was the most susceptible. Interestingly, in addition to the wild‐type (NCTC 11168) and cmeB mutant, also a mutant that lacks autoinducer‐2 production (luxS) was able to adhere (1 h) and to produce a biofilm (24, 48 and 72 h). The subinhibitory concentrations of all preparations at least partly inhibited C. jejuni adhesion and biofilm formation with the most visible effect of the quinolinone alkaloid fraction. Using a Vibrio harveyi luminescence assay, the inhibition of autoinducer‐2 production was observed in the wild‐type and cmeB mutant after 48 h with the most visible effect of EREE and its fraction Q. Copyright

Microbial adhesion capacity. Influence of shear and temperature stress

Environmental parameters dictate the conditions for both biofilm formation and deconstruction. The aim of this study is to analyse the impact of hydrodynamic and thermodynamic effects on bacterial detachment. Escherichia coli grown on two stainless steel metal surfaces with different roughness (brushed with roughness of 0.05 μm and electropolished with roughness of 0.29 μm) are exposed to laminar and turbulent (shower) flows of phosphate buffered saline media at temperatures of 8, 20 and 37 °C. Results show that the turbulent flow removes significantly more bacterial cells than laminar flow (p <0.05) on both materials. This indicates that the shear force determines the rate of detached bacteria. It is also observed that detachment of cells is more efficient on brushed than on electropolished contact surfaces because on the latter surface, fewer cells were attached before exposure. Moreover, we demonstrate that the temperature of the washing agent has an impact on bacterial detachment. At the same flow conditions, the exposure to higher temperature results in greater detachment rate.

Virulence genes and cytokine profile in systemic murine Campylobacter coli infection

Campylobacter coli are one of the most common bacteria in bacterial gastroenteritis and acute enterocolitis in humans. However, relatively little is known regarding the mechanisms of pathogenesis and host response to C. coli infections. To investigate the influence of genetic changes, we first used PCR to demonstrate the presence of the known virulence genes cadF, virB11, cdtB, cdtC and ceuE in the clinical isolate C. coli 26536, which was isolated from the liver of infected BALB/c mice. Sequence analyses of the cadF, virB11, cdtB and ceuE genes in C. coli 26536 confirmed the stability in these virulence genes during their transmission through the host. We further investigated C. coli infection for the bacterial clearance from the liver and spleen of infected mice, and for their immune response. C. coli persisted well in both organs, with better survival in the liver. We also determined the levels of several pro-inflammatory cytokines (i.e., interleukin [IL]-6, IL-12, interferon-γ, tumor necrosis factor-α) and the anti-inflammatory cytokine IL-10 in plasma and in liver homogenates from the infected mice, using enzyme-linked immunosorbent assays. The lowest levels among these cytokines were for tumor necrosis factor-α in the plasma and IL-6 in the liver on days 1, 3 and 8 post-infection. The most pronounced production was for IL-10, in both plasma (days 1 and 8 post-infection) and liver (day 8 post-infection), which suggests that it has a role in healing of the organ inflammation. Our findings showed dynamic relationships between pro- and anti-inflammatory cytokines and thus contribute toward clarification of the healing processes involved in the resolution of C. coli infections.

The influence of Dekkera bruxellensis on the transcriptome of Saccharomyces cerevisiae and on the aromatic profile of synthetic wine must

A double compartment membrane system was constructed in order to systematically study possible microbial interactions between yeasts Saccharomyces cerevisiae and Dekkera bruxellensis and their impact on wine aroma. The presence of D. bruxellensis induced 77 transcripts of S. cerevisiae. These were mostly of unknown function; however, some were involved in thiamine biosynthesis and in amino acid and polyamine transport, suggesting a competitive relationship between the two yeast species. Among the transcripts with no biological function, 14 of them were found to be the members of the PAU gene family that is associated with response to anaerobiosis stress. In separated cultures, S. cerevisiae produced glycerol which was subsequently consumed by D. bruxellensis. The concentration of ethylphenols was reduced and we assume that they were absorbed onto the surfaces of S. cerevisiae yeast walls. Also in separated cultures, D. bruxellensis formed a typical profile of aromatic esters with decreased levels of acetate esters and increased level of ethyl esters.

Food Safety Systems

Throughout the world, major shifts in food consumption at a global and regional level are occurring with considerable health consequences which results in increasing food safety and quality demands and requirements. A food safety management system is a set of interacting elements forming a network to ensure that food presents a minimal risk to consumers and includes good practices, HACCP system, management policies, traceability systems, and standards while considering food safety regulation. The vast numbers of laws, regulations, standards, good practices, and codes make everybody confused, even those who are working in the field on a regular basis and are forced to keep up with the developments. To achieve food-related disease prevention and efficient safe food assurance suitable for working environment from the hygienic-technical point of view, motivated, satisfied, and qualified personnel needs to be assured. Consumers are not connected to food supply chain according to chain principles. However, it has been shown that present maintenance of food safety in food supply chain can be easily broken down, because of different kinds of barriers or simple misunderstanding. Therefore, a new approach called “good nutritional practice” (GNP) was coined to manage food safety. It is important to reconstruct the existent food safety system with GNP which includes consumers and is based on a model that covers subsystems from other good practices through the food supply chain. There is also considerable interest in reducing humankind’s impact on the climate and invested effort has focused around the contribution that food makes to global warming such as carbon footprint, wastes, food miles, etc., and promotion of sustainable development. The Consumers Future Food reveals that there is a revolution, which raises ethical concerns all the way from stable to table, from farm to fork, from spring to drink. On the dinner tables of tomorrow, consumers may expect a new food icon that is the result of an evolution which is transforming the very nature of the food we eat with a view to create a new breed of future prospects for healthy and safe nutrition.

Food Supply Chains vs. Food Supply Nets

Public health care is directly connected with the assurance of healthy and safe food. Food systems are experiencing new possibilities in their practices due to rapid technical and technological advancements in the developed world. A hazard is a (micro)biological, chemical, physical agent or condition with the potential to cause adverse health effects. Managing hazards and surrounding circumstances does not mean that we completely manage safety. Currently, we master food safety via nine good practices, obligatory HACCP system and many standards on the food safety field. All current active practices are segregated along the food supply chain. Because they are not connected into a comprehensive system, there are many gaps in the food supply chain in which the potential for food hazard exposure exists. To reduce all such gaps in food supply chains, a food safety platform with the consumer as an active partner in Good Nutrition Practice appears to be the relevant choice for the current state of the development of food production processing and nutrition. A more effective system of primary education and the lifelong learning of food-related topics are needed. To achieve total quality and food safety, a multidisciplinary and an innovative approach, which would be capable of quick and effective responses in the food supply chain, is needed. Consequently, this adjusts system to multidimensional space with all relevant activities in time. All essential actions should be managed in the space between two layers, where all relations and control actions with different professional stakeholders and finally the consumer are determined. This led us from a chain to a network. The network approach would be much more relevant to interconnect all existing nodes in current food supply systems. This would involve and emphasize the importance of the subjective comprehension of health and safety concepts, which are a constituent part of well-being.

Vpliv naravnih protimikrobnih snovi na bakterijsko hidrofobnost, adhezijo in zeta potencial

Abstract Interactions between bacterial cells and contact materials play an important role in food safety and technology. As bacterial strains become ever more resistant to antibiotics, the aim of this study was to analyse adhesion of selected foodborne bacterial strains on polystyrene surface and to evaluate the effects of natural antimicrobials on bacterial cell hydrophobicity, adhesion, and zeta potential as strategies of adhesion prevention. The results showed strain-specific adhesion rate on polystyrene. The lowest and the highest adhesion were found for two B. cereus lines. Natural antimicrobials ferulic and rosmarinic acid substantially decreased adhesion, whereas the effect of epigallocatechin gallate was neglectful. Similar results were found for the zeta potential, indicating that natural antimicrobials reduce bacterial adhesion. Targeting bacterial adhesion using natural extracts we can eliminate potential infection at an early stage. Future experimental studies should focus on situations that are as close to industrial conditions as possible.