Papel da adição de bactérias autóctones do intestino de Colossoma macropomum na fisiopatologia da sepse

Abstract

Aeromonosis is a disease that causes hemorrhagic septicemia and frequently affects fish in farming systems, resulting in high mortality. It is known that the intestine plays an important role in the immune system and the composition of its microbiome is affected in septic individuals. Thus, correcting dysbiosis can be a strategy to alleviate the worsening of the septic process. Thus, the work aimed to analyze the effects on immunophysiology and microbiota in tambaquis, Colossoma macropomum, supplemented with strains of autochthonous probiotic bacteria during sepsis induced by Aeromonas hydrophila. The probiotic strains were isolated in previous tests from the intestine (I10) and from a mix of intestine and feces (M14) of tambaquis from the Amazon River. For the experiment, the fish received feed supplemented with each probiotic strain separately one (1) time (M14 1x and I10 1x) or 3 times a day (M14 3x and I10 3x), at a concentration of 3x109 CFU/mL and a dose of 15 mL/kg of feed, for 90 days and with a feeding frequency of 3 times a day for all groups. The control group did not receive a supplemented diet. After the supplementation period, the animals were challenged by inoculating the coelomic cavity with A. hydrophila (DL50% 1.78x108) and 24 hours after challenge (HPD), blood and intestine were collected for hematological, biochemical, innate immunity analyzes and intestinal microbiota. During the 24 HPD period, all fish showed signs of internal hemorrhage, with hemorrhagic fluid in the coelomic cavity and positive blood culture. In the erythrogram analysis, there was no difference (p>0.05) in relation to the control in hemoglobin concentrations (Hb) and mean corpuscular hemoglobin concentration (MCHC). There was a reduction in erythrocyte count and globular volume/hematocrit (VG) in the control group compared to the supplemented groups (p<0.05). In relation to the mean corpuscular volume (MCV), a reduction was observed for fish supplemented with strain I10 (p<0.05) and a reduction in mean corpuscular hemoglobin (HCM) levels in the supplemented groups (p<0.05). Leukopenia and thrombocytopenia were observed in the control group (p<0.05) compared to the supplemented groups. In serum biochemistry, a significant increase in triglyceride levels and a reduction (p<0.05) in aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were observed for all supplemented groups. The innate immune system variables showed increased lysozyme concentrations in fish supplemented with I10 3x and I10 1x and MPO was more active in those supplemented with M14 1x and I10 1x, without changes in ROS. In bacterial agglutination, the groups that received a diet supplemented with the mix strain had higher antibody titers. The metagenomic analysis allowed the identification of a greater abundance of bacterial species in the groups supplemented with probiotics, with emphasis on bacteria such as Cetobacterium somerae, which have proven probiotic effects, emphasizing the ability of M14 and I10 to interact with the beneficial microbiota resident in the fish. Furthermore, aeromonosis induced dysbiosis with a greater presence of bacteria of the genus Enterobacter in all groups. The results indicate that the autochthonous strains, mainly the strain isolated from the mix (M14), caused improvements in the immunological response and improved dysbiosis in the supplemented tambaquis.