Establishment of a model of Streptococcus iniae meningoencephalitis in Nile tilapia (Oreochromis niloticus).

Streptococcus iniae is an invasive pathogen causing meningitis and other lesions in various fish species. Furthermore, S. iniae is an emerging zoonotic agent that causes cellulitis in man. The aims of this study were to establish an intraperitoneal infection model for S. iniae in Nile tilapia (Oreochromis niloticus) and to develop a new histopathological scoring system to reflect the degree and extent of inflammation as well as the presence of necrosis in the brain and eye. Intraperitoneal administration of 10(6) colony-forming units (CFU) led to 80% mortality and numerous fish developing clinical signs of central nervous system dysfunction. Microscopical examination of four regions of the brain (olfactory bulb, cerebellum, cerebrum and optical lobe) and the eye revealed the presence of lymphohistiocytic leptomeningitis, meningoencephalitis and endophthalmitis. Lesions were dominated by macrophages that often contained intracellular bacteria. Necrosis was recorded in some cases. Bacteriological screening revealed that multiple organs, including brain and eye, were infected with S. iniae and S. iniae colonized the scales and gills in high number. S. iniae was detected in tank water during the first week post infection, suggesting that infected tilapia might shed up to 3 × 10(7) CFU of S. iniae within 24 h. A multiplex polymerase chain reaction allowed confirmation of the challenge strain by detection of the virulence factors simA, scpI, cpsD, pgi, pgm and sagA.

Detection of Mycoplasma bovis by in-situ hybridization and expression of inducible nitric oxide synthase, nitrotyrosine and manganese superoxide dismutase in the lungs of experimentally-infected calves.

Pneumonic lesions occurring in calves after respiratory infection with Mycoplasma bovis are characterized by subacute or chronic suppurative bronchopneumonia with multiple foci of necrosis and by persistence of M. bovis antigen, which is frequently associated with phagocytes at the periphery of the necrotic foci. The aims of this study were: (1) to investigate the expression of inducible nitric oxide synthase (iNOS), nitrotyrosine (NT) and manganese superoxide dismutase (Mn-SOD) in the lung lesions of calves infected experimentally with M. bovis, and (2) to analyse the distribution and localization of M. bovis DNA by in-situ hybridization and correlate these findings with the immunohistochemical detection of M. bovis antigen. Phagocytic cells infiltrating the lung tissue were characterized using the markers CD68, S100A8 and S100A9. Lung tissue from 18 infected calves and three non-infected controls were examined. All infected calves had an increased number of cells expressing iNOS, NT and Mn-SOD in the inflamed lung tissue. These molecules were most strongly expressed by macrophages demarcating necrotic areas, by altered bronchiolar epithelial cells and by macrophages within obliterated bronchioles. Co-localization of M. bovis DNA, M. bovis antigen and macrophages expressing iNOS, NT and Mn-SOD was observed. These findings suggest that the generation of reactive oxygen and nitrogen species is involved in the development of severe chronic lung damage in M. bovis infection.

Multiple cutaneous ganglioneuromas in a dog.

A 3-year-old male Labrador retriever dog was presented with multifocal small cutaneous nodules, distributed mainly over the thoracic wall, the flank and the scrotum. The dog was otherwise in good health and had no significant past medical history. Radio- and sonographic examination revealed no evidence of internal tumours, including endocrine tumours. Histological examination of two excised samples revealed round, non-ulcerated nodules in the superficial corium, characterized by two different neoplastic cell components and mild inflammation. The first tumour cell population showed histomorphological characteristics of mature ganglion cells; the second featured small, spindle-shaped tumour cells with scant cytoplasm. Both neoplastic cell components expressed vimentin, neurofilament protein, pan-neuronal neurofilament, amyloid-precursor protein and chromogranin A. In addition, the spindle-shaped tumour cells were positive for 2', 3'-cyclicnucleotide 3'-phosphodiesterase. The findings had many histological and immunohistochemical features in common with primary cutaneous ganglioneuromas in humans, enabling the canine tumours to be also classified as multiple cutaneous ganglioneuromas.