Bacterial Infection in Cultured Common Dentex (Dentex dentex, L. 1758)

The aim of this study is the identification of microbial agents recovered from 8 moribund common dentex (Dentex dentex) samples (140-200 g), determination of their antimicrobial susceptibilities and description of histopathological changes. Main clinical external and internal symptoms of bacterial haemorrhagic septicaemia cases such as fin base and liver haemorrhages, splenomegaly, accumulation of fluid in the intestines and peritoneal cavity were observed. Bacteriological samples of liver, kidney and spleen were streaked onto Marine Agar and Tryptic Soy Agar plates containing %1,5 NaCl and incubated at 22°C for 48h. Gram-positive non-motile cocci and Gram-negative motile bacillus were isolated from visceral organs. According to morphological and biochemical characteristics, isolates were identified as Micrococcus luteus and Vibrio sp. The Kirby-Bauer disk diffusion method was also performed using multidisc and all isolates were determined to be sensitive against kanamycin, oxytetracycline and flumequine. In the infected fish, general cell degenerations and necrosis in various tissues, a remarkable increase in the goblet cells of the intestines, hepatic lipidosis in the liver, hyperplasia in the gills and the presence of melanomacrophage centres in various tissues were demonstrated. As a result, here, a mixed infection in moribund fish samples was described and this is the first report on the histopathological changes of M. luteus infection in a marine fish species. This bacterium was detected as a possible pathogen of common dentex with various external, internal and histopathological damages