Edible bivalves as a source of human pathogens: signals between vibrios and the bivalve host

Main Category: Nutrition / Diet
Article Date: 26 May 2005 - 11:00 PDT

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Clams, mussels and oysters are important vehicles for the transmission of enteric diseases when consumed raw or undercooked. Vibrio species, including human pathogens, are particularly abundant in bivalve tissues, where they can persist even after cleaning procedures, thus representing a potential risk for human health. Although different environmental factors are well known to affect the persistence of vibrios in these organisms, the key role of the interactions between vibrios and the immune system of bivalves has been recently highlighted by scientists from the Universities of Genova and Urbino (Italy) in Environmental Microbiology.

Carla Pruzzo, from the University of Genova explains: "In bivalves, immunity is carried out by circulating haemocytes and soluble haemolymph factors that act in a co-ordinate way to kill microorganisms. Our research examines available data on Vibrio interactions with both cellular and soluble components of the bivalve immune system in the light of the capacity of bacteria to evade the hemolymph bactericidal activity and to develop pathogenic effects in the bivalve host."

The authors describe their data obtained with an in vitro model of Vibrio cholerae challenged against the immune system of Mytilus galloprovincialis, chosen as representative of important and appreciated seafood in the Mediterranean area. The results obtained allowed the identification of factors that are important in determining the fate of vibrios within the bivalve host, such as bacterial surface ligands, soluble hemolymph components and the ability of bacteria to affect distinct signaling pathways responsible for the hemocyte immune response.

Laura Canesi, from the University of Urbino adds "In bivalve hemocytes, different Vibrio species and strains seem to adopt a common strategy utilized by pathogenic bacteria in mammalian cells: to undermine host cell functions through disregulation of its signaling pathways".

This research gives an insight into the complexity of signals that pass between vibrios and bivalve host cells and helps to explain how these processes develop in natural conditions and determine the fate of vibrios in the bivalve host.

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