Bacterial and pathological study of caudal fin rot in brood stocks of Salmo trutta caspius from the propagation and breeding center of Shahid Bahonar of Kelardasht region

In order to study caudal fin rot with emphasis on Aeromonas hydrophila and Pseudomonas fluorescens in Salmo trutta caspius from the salmonids propagation and breeding center of Shahid Bahonar of kelardasht region, One hundred and eighty brood stocks having fin damage symptoms were chosen. Two bacterial samples from each fish were cultured on Aeromonas and Pseudomonas specific media. Biochemical tests, API2OE identification system and antibiogram test using six antibiotic disks were performed for diagnosing isolates bacteria and finding suitable antibiotic. Thirty samples from caudal fin of damaged fishes were fixed in 10% formalin and 51.tm microscopic sections were prepared using standard scatological methods and then stained by Haematoxylin-Eosin staining method to observe the pathological changes and also Maccallum-Goodpasture staining method to observe the bacterial colonies. In second stage of the study, bacterial samples were taken from thirty brood stocks using similar method at the first stage of sampling. For isolation and biochemical diagnosis of Aeromonas and Pseudormonas genus, the samples were analyzed by molecular research included PCR amplification (using 16S rDNA genes of the genus pseudomonas and 16S-23S rDNA intergenic spacer of the genus Aeromonas) and restriction analysis by four restriction enzymes for each genus. The results of biochemical tests showed that isolated bacteria were belonged to Aeromonas caviae and Aeromonas hydrophila (subspecies anaerogenes), Pseudomonas fluorescens, Pseudomonas putida and Pseudomonas alcaligenes while the results of API2OE identification system showed that the isolated bacteria belonged to Aeromonas hydrophila, Pseudomonas fluorescens, Pseudomonas putida and Pseudomonas aeruginosa. Restriction analysis of Aeromonas samples with Hin6l, Csp6I, Taql, and Tasl revealed three samples were different from others while restriction analysis of Pseudomonas samples with Alul, Hinfl, Rsal, and Trull showed at least five species or biovars. The results of antibiogram test showed all Aeromonas samples were sensitive to Trimethoprim, Chloramphenicol and Nitrofurazone, mostly to Nalidixic acid and Chloramphenicol, while most of samples were resistant to Erythromycin and Oxytetracycline. Pseudomonas samples were only sensitive to Nitrofurazone and mostly resistant to Oxytetracycline, Nalidixic acid, Erythromycin, Trimethoprim and Chloramphenicol. The results of light microscope study showed hyperplasia and spongiosis of the malpigian cells of epidermis, increasing of melanin pigments underlying epidermis; sever necrosis in both epidermis and dermis and also sloughing the epidermis in some cases. Occurrence of clefts through the epithelium, neovascularization, hyperemia and mild inflammatory response in dermis and separation of the fin rays also were observed. No bacterial colonies were found in the sections.

Study of nephrocalcinosis in rainbow trout (Oncorhynchus mykiss), from fry to brood stock

For survey incidence of nephrocalcinosis in rainbow trout fish, during winter 1385, samplings were performed in three fish farm with different water source: river, spring and recirculation system by using well water. In this survey 5 specimens from each 8 groups and in general 120 specimens of this fish were caught by random sampling, and also amounts of O2, CO2, pH and temperature of water were measured. Then blooding and renal tissue sampling performed that renal samples were fixed in 10% buffered formalin and blood samples after separating serum stored in -200C. Renal specimens transferred to pathology laboratory, pathological slides were prepared and stained by hematoxylin & Eosin method. From 120 specimens, 6 cases of fish represent nephrocalcinosis. Pathologic signs include: renal epithelial necrosis, dilated ureters, dense basophilic materials inside the dilated tubules and cast formation in some renal tubules. From 6 cases of nephrocalcinosis, 3 cases (7/5%) were related to recirculation system and 2 (5%) case were related to river water and 1 (2/5%) case was related to spring water. In survey amount of urea, creatinine and Uric acid between different weight groups, distinguished that difference between creatinine middling in different weight groups were significant and also in between healthy and afflicted fish, significant statistical difference were only in creatinine amount between healthy and afflicted fish in each farm. Amounts of O2, pH and temperature of water in three farms were in normal range and only rate of water CO2 in ponds of recirculatory system were very higher (25 mg/lit) than other farms. May be, this reason led to high number of nephrocalcinosis in recirculatory system, than other farms, nemley 7/5% of fish that caught from this farm .This subject is related to the role of CO2 in creating nephrocalcinosis which is descript in references.