Infection routes of Aeromonas salmonicida in rainbow trout monitored in vivo by real‐time bioluminescence imaging

Abstract

Recent development of imaging tools has facilitated studies of pathogen infections in vivo in real time. This trend can be exemplified by advances in bioluminescence imaging (BLI), an approach that helps to visualize dissemination of pathogens within the same animal over several time points. Here, we employ bacterial BLI for examining routes of entry and spread of Aeromonas salmonicida susbp. salmonicida in rainbow trout. A virulent Danish A. salmonicida strain was tagged with pAKgfplux1, a dual-labelled plasmid vector containing the mutated gfpmut3a gene from Aequorea victoria and the luxCDABE genes from the bacterium Photorhabdus luminescens. The resulting A. salmonicida transformant exhibited growth properties and virulence identical to the wild-type A. salmonicida, which made it suitable for an experimental infection, mimicking natural conditions. Fish were infected with pAKgfplux1 tagged A. salmonicida via immersion bath. Colonization and subsequent tissue dissemination was followed over a 24-h period using the IVIS spectrum imaging workstation. Results suggest the pathogen's colonization sites are the dorsal and pectoral fin and the gills, followed by a progression through the internal organs and an ensuing exit via the anal opening. This study provides a tool for visualizing colonization of A. salmonicida and other bacterial pathogens in fish.

Effective isolation of GALT cells: Insights into the intestine immune response of rainbow trout (Oncorhynchus mykiss) to different bacterin vaccine preparations

“…After A. salmonicida colonizes the intestine of rainbow trout it subsequently disseminates into the fish body, in a pattern similar to that seen with the dissemination of another Gramnegative fish pathogen Yersinia ruckeri, the causative agent of enteric redmouth disease (ERM) in salmonids [24]. Y. ruckeri colonizes the intestine of rainbow trout 2-4 days prior to systemic infection, indicating the contribution of the intestine to the systemic dissemination of the invading pathogen [25].…”

Pinpointing the role of Aeromonas salmonicida in the development of skin ulcerations in common dab (Limanda limanda)

“…The extent to which and the adopted mechanism needs to be further elucidated. In following studies, to pinpoint the underlying pathogenesis, an infection with bioluminescent bacteria could be recommended combined with a sequential and controlled sampling during the development of the disease, as suggested by Bartkova, Kokotovic, and Dalsgaard () and Menanteau‐Ledouble, Karsi, and Lawrence (). Immunohistochemical staining can also be helpful to locate the bacteria during different stages of the disease.…”

Vaccine-Induced Protection Against Furunculosis Involves Pre-emptive Priming of Humoral Immunity in Arctic Charr

“…The bacterium is thought to enter the fish host at multiple sites, including the skin, gill, and intestine (79). The typical incubation period of Asal is 3–4 days, where the bacterium rapidly disseminates in kidneys, followed by the spleen, liver, and muscles (80).…”