Inflammatory Effects of Edwardsiella ictaluri Lipopolysaccharide Modifications in Catfish Gut

Abstract

e Bacterial lipopolysaccharides (LPS) are structural components of the outer membranes of Gram-negative bacteria and also are potent inducers of inflammation in mammals. Higher vertebrates are extremely sensitive to LPS, but lower vertebrates, like fish, are resistant to their systemic toxic effects. However, the effects of LPS on the fish intestinal mucosa remain unknown. Edwardsiella ictaluri is a primitive member of the Enterobacteriaceae family that causes enteric septicemia in channel catfish (Ictalurus punctatus). E. ictaluri infects and colonizes deep lymphoid tissues upon oral or immersion infection. Both gut and olfactory organs are the primary sites of invasion. At the systemic level, E. ictaluri pathogenesis is relatively well characterized, but our knowledge about E. ictaluri intestinal interaction is limited. Recently, we observed that E. ictaluri oligo-polysaccharide (O-PS) LPS mutants have differential effects on the intestinal epithelia of orally inoculated catfish. Here we evaluate the effects of E. ictaluri O-PS LPS mutants by using a novel catfish intestinal loop model and compare it to the rabbit ileal loop model inoculated with Salmonella enterica serovar Typhimurium LPS. We found evident differences in rabbit ileal loop and catfish ileal loop responses to E. ictaluri and S. Typhimurium LPS. We determined that catfish respond to E. ictaluri LPS but not to S. Typhimurium LPS. We also determined that E. ictaluri inhibits cytokine production and induces disruption of the intestinal fish epithelia in an O-PS-dependent fashion. The E. ictaluri wild type and ⌬wibT LPS mutant caused intestinal tissue damage and inhibited proinflammatory cytokine synthesis, in contrast to E. ictaluri ⌬gne and ⌬ugd LPS mutants. We concluded that the E. ictaluri O-PS subunits play a major role during pathogenesis, since they influence the recognition of the LPS by the intestinal mucosal immune system of the catfish. The LPS structure of E. ictaluri mutants is needed to understand the mechanism of interaction.

Effects of Vitamin D2 (Ergocalciferol) and D3 (Cholecalciferol) on Atlantic Salmon (Salmo salar) Primary Macrophage Immune Response to Aeromonas salmonicida subsp. salmonicida Infection

“…Total RNA from Atlantic salmon primary macrophages was extracted using 1 ml of TRIzol Reagent (Invitrogen), and purified using the RNeasy R Mini Kit (QIAGEN) following the manufacturer's instructions (44). RNA samples were treated with 2 U of TURBO DNase (TURBO DNA-free TM Kit, Invitrogen) following the manufacturer's instructions to degrade any residual genomic DNA.…”

The NCK and ABI adaptor genes in catfish and their involvement in ESC disease response

“…Actin polymerization and receptor-mediated endocytosis are involved in the uptake of E. ictaluri by rat small intestinal epithelial cells (Skirpstunas and Baldwin, 2002). It was corroborated that E. ictaluri lipopolysaccharide oligo-polysaccharide (LPS O-PS) plays a major role during catfish intestinal infection and immune protective stimulation, since they influence the recognition of the LPS by the intestinal mucosal immune system of catfish (Santander et al, 2014). However, the internalization process of E. ictaluri into its natural host, channel catfish, together with the involved pathways, genes, and coordinators are still unknown.…”

“…ESC, caused by the bacterium Edwardsiella ictaluri, is one of the most severe bacterial diseases in catfish. Although E. ictaluri pathogenesis is relatively well characterized, the knowledge about E. ictaluri intestinal interaction is limited (Santander et al, 2014). Besides, little is known about the molecular mechanism of pathogenicity of E. ictaluri.…”

Edwardsiella Species Infection in Fish Population and Its Status in Ethiopia

“…show abnormal swimming behavior, including spiral movement and floating near the water surface or hang head up in the water column disoriented behaviors characterized by a corkscrew swimming motion [34,35]. Although clinical signs vary after onset, fish infected with this bacteria show loss of pigmentation, exophthalmia, opacity of the eyes, swelling of the abdominal surface, petechial hemorrhage in fin and skin, ulceration, enteritis in acute disease, a soft, fluctuant red swelling on the dorsum of the head in chronic disease and swollen anus due to the accumulation of ascitic fluid [34,[36][37][38].…”