Changes of intestinal mucus glycoproteins after peroral application of Aeromonas hydrophila to common carp (Cyprinus carpio)

Mucus forms a biofilm that protects the underlying epithelium Interactions between this mucus layer and bacteria are important in most infectious diseases. Aeromonas hydrophila, a widespread bacterium in the aquatic environment, is often isolated during disease outbreaks in fish. This study investigates biochemical properties of intestinal mucus glycoproteins of common carp, Cyprinus carpio L, in response to peroral application of two strains of A. hydrophila (strains 38 and 60). Application of A. hydrophila altered intestinal secretion and composition of intestinal mucus glycoproteins in carp. Application of A. hydrophila 60 resulted in a significant increase in mucus glycoproteins. In contrast a striking reduction in the amount and molecular size of mucus glycoproteins was observed upon administration of A. hydrophila 38. Simultaneous changes in the glycosylation pattern of isolated glycoproteins were found. The intestinal mucosal system is supposed to provide a removal mechanism for bacterial noxes by increased secretion of mucins inducing a washing out effect. Data from this study indicate that modulation of secretion and glycosylation depends on the applied A. hydrophila strain. Application of A. hydrophila 60 leads to an increased secretion of small mucus glycoproteins, which may lead to a flushing out of the bacteria and therefore to an elimination of bacterial noxes. Manifestation of the bacteria seemed to be prevented. In contrast the application of A. hydrophila 38 apparently destroys the mucus layer, leaving the intestinal mucosa insufficiently protected against further pathogens, which then have the capability to invade the underlying tissue and induce disease. (C) 2008 Elsevier B.V. All rights reserved.