ABSTRACT
Russian sturgeon (Acipenser gueldenstaedtii) is an endangered fish species and also an important resource for the sturgeon aquaculture industry in Turkiye. Recently, a fatal and persistent bacterial disease occurred in the reared sturgeon kept in a trout farm in Turkiye. The disease outbreak has been with notable external signs including petechial hemorrhages and systemic anemia. This outbreak lasted for six weeks, and cumulative mortality reached around 35.00 - 40.00%. In this study, no parasitic and viral agents were observed in the sturgeons. Citrobacter gillenii was isolated from the diseased fish and identified by biochemical and molecular methods including API 20E and 20NE and 16S rRNA gene region sequencing, respectively. As a result, C. gillenii was identified for the first time in Russian sturgeon in Turkiye. The sequence was also deposited under the Genbank with MW057770 accession number. According to the result of disc diffusion method, bacteria were sensitive to enrofloxacin, streptomycin, amoxicillin and oxytetracycline and resistant to penicillin, trimethoprim/sulfamethoxazole, florfenicol and erythromycin. Also, ampC, sul1 and floR resistance genes were detected in the isolated bacteria. The results of this study provide important information for the diagnosis and treatment of this newly emerged disease of Russian sturgeon.
ABSTRACT
Triclosan (TRC), chloroxylenol (PCMX) and methylisothiazolinone (MIT) have been commonly used as an antimicrobial in soaps while borax (BRX) is used in household cleaning. After using these chemicals, they are washed down drains and getting into the aquatic ecosystem in which they may affect aquatic living organisms. In the present study, the chronic effects of TRC, PCMX, MIT and BRX on genotoxicity, gene expression and histopathology of rainbow trout (Oncorhynchus mykiss) were evaluated for 40 days under semi static condition. The comet assay results indicated that MIT, TRC and PCMX caused significant DNA damage to erythrocytes of the fish. Transcription of SOD, GPX1, GPX2, GSTA, HSP90BB, HSP90BA, CAT, and HSC70A genes were significantly regulated as a result of TRC, PCMX, MIT, and BRX exposure except PCMX exposed GSTA gene. Histological lesions were detected in gills, spleen liver, and trunk kidney of the fish. Lamellar fusion, hyperplasia and epithelial necrosis in gills, melanomacrophage centers and splenic necrosis in spleen, pyknotic nucleus, fat vacuoles, necrotic hepatocytes in liver, cloudy swelling in the tubules, renal tubule epithelial cells degeneration, glomerular capillaries dilation and glomerulus degeneration in kidney, were observed. Our study demonstrates the chronic toxic effect of TRC, PCMX, MIT, and BRX is high in rainbow trout. Therefore, we should be more careful when using these chemicals for cleaning in order to protect aquatic environment.
