Egg white kills [i]Bacillus cereus[/i] group bacteria through a mechanism involving ovotransferrin
Résumé
Egg white antimicrobial activities are widely investigated regarding the resistance of Salmonella enterica
serovar Enteritidis. This resistance is considered as one on the main factors explaining the high prevalence of this serovar in egg-product-related food-borne disease. The behavior of Gram-positive bacteria has been poorly investigated in egg white whereas it can provide additional insight into the bacterial response to this iron-deprived harsh medium. Investigating the behavior of Gam-positive bacteria in egg white may then provide new insights into the mechanisms of bacterial pathogenesis and adaptation in the hos
t iron-deprived environment. Bacillus cereus is a Gram-positive spore-forming opportunistic human bac
terium frequently associated with foodborne infections due to the production of diarrheal and e metic toxins. Psychrotrophic B. cereus group strains are recognized as being involved in spoilage events of chilled pasteurized liquid whole egg products due to their ability to secrete hydrolytic enzymes, even at low temperature. Their behavior in an egg product such as egg white warranted furth er consideration since this ingredient is widely used in the production of food particularly sensiti ve from a microbiological perspective, such a chilled lightly cooked desserts comprising egg white foams (chocolate mousse, floating island, etc.). These facts led us to investigate the behavior of B. cereus group bacteria in egg white. Our results
highlighted a strong bactericidal effect at permissive temperature (30°C) and under the natural
alkaline (natural pH of 9.3 a few days after laying ) and iron-deprived conditions of egg white. This bactericidal effect could be ascribed to a well-kno wn egg white protein, ovotransferrin, which to date had exclusively been described as responsible for bacteriostasis due to iron chelation. The addition of iron reversed this bactericidal effect only under neutral incubation conditions. A perturbation of the electrochemical potential of the cytoplasmic membrane suggested that an ovotransferrin-mediated membrane disturbance mechanism could be involved in bacterial death in egg white.
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Jan et al. Paris-2015-3_{C02B45C2-8695-49F6-A5E0-14B33CE1B572}.pdf (205.36 Ko)
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