جستجوی مقالات مرتبط با کلیدواژه « polymerase chain reaction » در نشریات گروه « شیلات »

Bacterial diseases are a major challenge and warning to the development of aquaculture industry. Vibriosis is caused by bacteria of the genus Vibrio, especially Vibrio alginolyticus, in warm and temperate regions, which cause severe damages to the marine fish production economy every year. The aim of the present study was to isolate and identify this bacterium from farmed marine fish with bacterial septicemia symptoms in the farms of the southern provinces of the Iran. A total of 130 fish were sampled and isolated bacterial samples by conventional methods. Isolates were examined for biochemical and molecular properties using specific primers of 16 S rRNA and Collagenase genes to identify Vibrio sp. and alginolyticus species by polymerase chain reaction, respectively. Molecular analysis showed that 109 isolates out of 119 suspected isolates of Vibrio genus were confirmed as Vibrio genus; also, 48 isolates belonged to V. alginolyticus. It is concluded that the cause of more than 44% of cases of vibriosis is caused by infection with V.alginolyticus. For the LD50 determination, 250 Asian sea bass were used and the lowest LD50 calculated for Vibrio alginolyticus isolates was 1.83× 10 8 fish/CFU. The results showed a significant role of vibriosis as well as a high percentage of V. alginolyticus in bacterial septicemia in the studied fish.

Streptococci and lactococci are among bacterial diseases of wild and farmed fish especially rainbow trout and accounted for significant economical losses in the aquaculture industry. In this study, 60 fish from rainbow trout farms in Ilam, were collected and sampled for bacterial and molecular analyses. Identification of the isolated bacteria was determined using biochemical tests and confirmed by polymerase chain reaction (PCR). For this purpose, using primer sets targeting portions of the tuf (code along factor Tu) and 16S rRNA gene sequences were performed to determine the genus Streptococcus and Streptococcus iniae, respectively. In total, 110 isolates belonging to the genus Streptococcus, Lactococcus and Staphylococcus were detected. Molecular tests showed that 90 isolates were Streptococcus genus, of which 35 isolates tested by species-specific primers were identified as Streptococcus iniae and the rest (55 isolates) belonged to the species Lactococcus garvieae. Subsequently, phenotypic and genotypic evaluations of antibiotic-resistance of the isolates were performed, using disk diffusion method and PCR targeting tet, erm and str genes. The results showed that of the 110 isolates of Gram-positive cocci, 39 isolates were resistant against streptomycin (35%), 26 to erythromycin (23%), 35 to oxytetracycline (31%), 30 to enrofloxacin (27%), 21 to florfenicol (19%) and 33 isolates were resistant to penicillin G (30%). The presence of streptococcosis / lactococcosis was confirmed among fish farms in Ilam within this study. Moreover, it seems that the indiscriminate use of antibiotics has led to stablish resistant against such infectious agents.