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Abstract The biochemical mechanisms involved in phagocytosis and the intracellular survival of Aeromonas hydrophila (Ah) in host macrophages (MΦs) are complex processes that affect infection success or failure. Thus, in the present study, we described the in vitro infection of Nile tilapia MΦs by a homologous bacterium and tested the effects of anti- A. hydrophila immunoglobulin Y (IgY) on the phagolysosomal activity and intracellular survival of the pathogen. The anti- Ah IgY modulated lysosomal acid phosphatase (LAP) activity as well as the production of reactive oxygen intermediates (ROIs) and nitric oxide (NO), thereby potentiating phagocytosis and the elimination of Ah. Thus, we assume that the specific IgY had a beneficial effect on infection control and postulated the use of the Nile tilapia MΦs as an important in vitro experimental model for the functional and therapeutic study of Ah infection. Highlights • The inoculation with MPs of Ah in the swim bladder of tilapia allowed the harvesting of activated macrophages. • Culture of the tilapia macrophages allowed the study of the phagocytic process during infection by Ah. • The IgY specificity for proteins from Ah neutralized the adhesion molecules and possible endo/exotoxins. • IgY modulated phagolysosomal activity, reducing the intracellular survival of Ah in the MΦs controlling the infection. [ABSTRACT FROM AUTHOR]

Abstract Aeromonas hydrophila (Ah) are rod-shaped, Gram-negative, motile aquatic bacteria that can infect fish and mammals, including humans. Due to the importance of this pathogen for fish farming and public health, the present study produced a specific immunoglobulin (Ig) Y by immunizing laying hens with Ah cell proteins. The antibody efficacy in detecting Ah was tested by direct immunofluorescence and indirect immunohistochemistry using tissues from infected Nile tilapia. The produced IgY exhibited specificity and affinity for membrane and cytoplasmic Ah proteins, which enabled detection of the intracellular localization of the bacteria and their proteins within the phagosomes of phagocytes and detection of extracellular bacteria colonizing host tissues. Thus, the findings offer a new perspective on the use of IgY for the diagnosis and analysis of Ah pathogenesis in Nile tilapia. Graphical Abstract Unlabelled Image Highlights • The produced IgY exhibited specificity and affinity for Aeromonas hydrophila proteins. • The multispecificity of IgY enabled intracellular detection of A. hydrophila within phagocytes and extracellular detection of free colonies in tissues. • The specific IgY enabled immunodiagnosis and analysis of A. hydrophila infection kinetics. [ABSTRACT FROM AUTHOR]

Abstract: Oreochromis niloticus bred in net cages were supplemented with cell wall of Saccharomyces cerevisiae (Sc) (0.3%) or chromium carbochelate (Cr) (18 mg/kg of feed) or in association (Sc + Cr), for 90 days. After this period, acute inflammation was induced in the swim bladder by inoculation of 3 × 108 CFU of inactivated Streptococcus agalactiae, and another group received 0.65% saline solution (control). Twelve, 24, and 48 h after stimulation, the inflammation was evaluated through total and differential counting of accumulated cells, and through leukocyte respiratory burst in the blood, cortisolemia, glycemia and serum lysozyme concentration. The results showed that there were greater total numbers of cells in the exudate of fish inoculated with inactivated bacterium than in those injected with saline solution, with predominance of lymphocytes, thrombocytes, macrophages and granulocytes. Tilapia supplemented with Cr presented increased total numbers of cells with significant accumulation of lymphocytes and reductions in cortisolemia and glycemia, but the different treatments did not have any influence on leukocyte respiratory burst or serum lysozyme concentration. Tilapia supplemented with Sc and the Cr + Sc association did not present significant changes to the variables evaluated, despite higher accumulation of lymphocytes in the inflammatory exudate from fish treated with Sc. The results indicate that tilapia bred in net cages and supplemented with Cr presented higher total accumulation of cells at the inflammatory focus, thus indicating an increase in the inflammatory response induced by the bacterium, probably due to the reduction in cortisolemia and higher glucose consumption. Thus, supplementation with Cr had beneficial action, which facilitated development of acute inflammation induced by the bacterium, but did not affect neither leukocyte respiratory burst in the blood nor serum lysozyme concentration. [Copyright &y& Elsevier]

Abstract: A total of 360 pacus (Piaractus mesopotamicus) were used to study vascular permeability (VP) and inflammatory cell component (CC) in induced aerocystitis in P. mesopotamicus through inoculation of inactivated Aeromonas hydrophila, and the effect of steroidal and nonsteroidal anti-inflammatory drugs. It was observed that after inoculation of A. hydrophila, the maximum VP occurred 180 min post-stimulus (MPS). Pretreatment with anti-inflammatory drugs inhibited VP, and the inhibitory effect of dexamethasone was seen earlier than the effects caused by meloxicam and indomethacin. Inoculation of the bacterium caused a gradual increase in the accumulation of cells, which reached a maximum 24 h post-stimulus (HPS). Pretreatment with dexamethasone, indomethacin and meloxicam reduced the accumulation of lymphocytes, thrombocytes, granulocytes and macrophages. There was no significant difference between the different doses of the drugs tested. The results suggest that eicosanoids and pro-inflammatory cytokines participate in chemical mediation in acute inflammation in pacus. [Copyright &y& Elsevier]