Localization analysis of fluorescent-labeled Aeromonas veronii in the intestinal tract of carp using an in vivo imaging system

Abstract

Aeromonas veronii is a Gram-negative opportunistic pathogen in fish. We have previously investigated the intestinal microbiota of carp Cyprinus carpio and revealed that most bacterial isolates with high mucus-binding capability were A. veronii. With regard to infection, mucosal adhesion of bacteria is regarded as a prerequisite for colonization and invasion. In the present study, we selected three A. veronii strains with different mucus-binding capability and pathogenicity, and compared the colonization capability and localization of these strains in the intestinal tract of carp, using an in vivo imaging system. We showed that only a pathogenic strain was mainly visible around the intestinal bulb and rectum of the intestinal tract at 48 h after administration. Frozen sections with fluorescence signals revealed that the administered bacteria were localized on the mucosal surfaces and in the lamina propria of the intestinal bulb, whereas they were mainly detected in the remaining intestinal contents in the rectum. These results suggest that the intestinal bulb is the primary region for A. veronii to invade and proliferate in healthy carp. © 2012 The Japanese Society of Fish Pathology.