RESUMO
Nile tilapias (Oreochromis niloticus) were intraperitoneally infected with a Streptococcus agalactiae suspension containing 10 CFU/mL. The strain of S. agalactiae used to experimental infection was isolated from naturally infected tilapias from Paraná, south Brazil. Fishes were kept in laboratory aquaria with adequate limnologic parameters, being euthanized 3, 7, 14, 21 and 28 days post-inoculation. The isolate caused exophtalmia, ocular opacity, erratic swimming, lethargy and darkness of the skin 3, 7 and 14 post-inoculation. Histopathology revealed a septicemia with a severe mononuclear infiltrate in meninges, epicardium and eyes. Inflammation occurred mainly 3 and 7 days post-inoculation, and at 21 and 28 days was not observed. A significant association was verified between infection with S. agalactiae and the presence of melanomacrophages centers in the liver and spleen. S. agalactiae was reisolated from brain and kidney 3, 7 and 14 days post-inoculation.
Assuntos
Animais , Infecções Estreptocócicas/veterinária , Streptococcus agalactiae/ultraestrutura , Sepse/veterinária , CiclídeosRESUMO
Light and electron microscopy were used to analyse the process of interaction of Streptococcus agalactiae (serotypes Ia, III, and V) with resident and activated mouse peritoneal macrophages. Transmission electron microscopy showed that adherence of the S. agalactiae serotype Ia, but not III and V serotypes, to the surface of activated macrophages triggers the respiratory oxidative burst as revealed by the presence of reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H]-oxidase in the phagocytic vacuoles. Fusion of macrophage lysosomes with bacteria-containing phagocytic vacuoles was observed in macrophages treated with Lucifer yellow as well as by localization of acid phosphatase for all serotypes.