Abstract/Summary

Ovotransferrin (OT) is the most abundant antimicrobial protein of egg white (EW). As eggs and egg products are often involved in salmonellosis outbreaks, this study aimed to gain a better understanding of (i) the role of OT in disturbing the growth and membrane functions of Salmonella Enteritidis and (ii) the ability of the bacteria to counteract the antimicrobial activity of this protein. The metal-chelating activity of OT was confirmed to be responsible for the antimicrobial activity of EW against S. Enteritidis. The importance of siderophores to support S. Enteritidis growth when OT is fully saturated was suggested. However, in the absence of iron the production of siderophores does not seem to confer any advantage for bacterial growth. The insufficient production of siderophores and/or the sequestration of Ent by lipocalins could explain this observation. The capacity of OT to induce S. Enteritidis membrane damage independently of its metal-chelating activity was strongly observed. Thus, OT can permeabilise the outer membrane and participate in the depolarisation of the inner membrane. The maintenance of membrane integrity is supported through the expression of different systems such as the Phage Shock Protein (Psp) genes. In this study, the expression of the psp genes seemed to be closely related to the alkaline pH of the medium employed. However, both EW and OT appeared to have only modest roles in the psp response, which depended on the concentration employed and the time of exposure. This study confirms the antimicrobial action of OT against S. Enteritidis in EW (metal-chelating activity, membrane perturbations).