The Pathogen Aeromonas salmonicida achromogenes Induces Fast Immune and Microbiota Modifications in Rainbow Trout

Abstract

Environmental stressors can disrupt the relationship between the microbiota and the host and lead to the loss of its functions. Among them, bacterial infection caused by Aeromonas salmonicida, the causative agent of furunculosis, results in high mortality in salmonid aquaculture. Here, rainbow trout were exposed to A. salmonicida achromogenes and its effects on the taxonomic composition and structure of the microbiota was assessed on different epithelia (gills, skin, and caudal fin) at 6 and 72 h post-infection (hpi) using the V1–V3 region of the 16S rRNA sequencing. Moreover, the infection by the pathogen and immune gene responses were evaluated in the head kidney by qPCR. Our results suggested that α-diversity was highly diverse but predominated by a few taxa while β-diversity was affected very early by infection in the gills after 6 h, subsequently affecting the microbiota of the skin and caudal fin. A dysbiosis of the microbiota and an increase in genera known to be opportunistic pathogens (Aeromonas, Pseudomonas) were also identified. Furthermore, an increase in pro-inflammatory cytokines and virulence protein array (vapa) was observed in trout head kidney as soon as 6 hpi and remained elevated until 72 hpi, while the anti-inflammatory genes seemed repressed. This study suggests that the infection by A. salmonicida achromogenes can alter fish microbiota of gills in the few hours post-infection. This result can be useful to develop a non-invasive technique to prevent disease outbreak in aquaculture.

Detection of Nucleic Acids of the Fish Pathogen Yersinia ruckeri from Planktonic and Biofilm Samples with a CRISPR/Cas13a-Based Assay

“…Thus, by coupling the CRISPR/Cas13a/crRNA gyrA platform to a lateral flow assay kit (HybriDetect, Milenia Biotec), we were able to detect, also specifically and with high sensitivity, Y. ruckeri from biofilm samples ( Figure 2 ). This lateral-flow-based method, coupled to the CRISPR/Cas system, had already been tested with high sensitivity in the detection and identification of other types of samples and organisms [ 16 , 43 ], but had not been tested on biofilm samples of fish pathogens. Developing effective detection and diagnostic tools based on this platform could be crucial to minimize the impact of Y. ruckeri on fish populations and improve overall aquaculture management to reduce the transmission of this and other fish pathogens.…”

Application of 4 × 44 Oligo Microarray to Transcriptomic Analysis of Immune Response in Rainbow Trout Infected with Aeromonas salmonicida

“…Further, the expressions of il1b and il11 significantly increased at 2 dpi (FC = 6.49 and FC = 8.14, respectively) and decreased after 6 dpi. IL1b is a key proinflammatory cytokine, which was also up-regulated at early stages of infection in the gill of rainbow trout [20] and Atlantic cod [27], as well as in the head kidney infected with A. salmonicida achromogenes [70]. IL11 belongs to the il6 cytokine family and plays a major role in hematopoiesis, and it may show pro-and anti-inflammatory responses in fish [70].…”

“…IL1b is a key proinflammatory cytokine, which was also up-regulated at early stages of infection in the gill of rainbow trout [20] and Atlantic cod [27], as well as in the head kidney infected with A. salmonicida achromogenes [70]. IL11 belongs to the il6 cytokine family and plays a major role in hematopoiesis, and it may show pro-and anti-inflammatory responses in fish [70]. In contrast to other interleukins, il17d was repressed in moribund fish and then came back to the control level in the survivors.…”