الفهرس | Only 14 pages are availabe for public view |
Abstract Yersiniosis is an infectious disease which produces high mortalities and severe economic losses in freshwater fish farms. Heavy mortalities were found in Oreochromis niloticus, Clarias gariepinus. at dakahlia. A total number of 200 freshly dead fish were sampled and transferred as soon as possible to the lab for clinical examination and bacteriological identification. The examined fish showed the septicemic signs of Yersiniosis which appeared as generalized erythema, petechial hemorrhages on the skin, fin erosions, protruded hemorrhagic vent with red erythematic hemorrhages on mouth and lips. Postmortem examination revealed engorged gall bladder, hemorrhagic gills, liver, gastrointestinal tract (GIT)and darkened congested spleen. After bacterial isolation from spleen, kidney, liver on specific culture media, diagnosis was achieved by conventional biochemical tests, serotyping and polymerase chain reaction (PCR). Antimicrobial was conducted on bacterial isolates in order to find the most suitable antibiotic for controlling this bacterial infection. from this study, it was found that the recommended antibiotic for controlling this bacterial infection is ciprofloxacin or Sulphamethoxazole-Trimethoprim combination. In this study Yersinia ruckeri is a common fish pathogen, it causes one of the most significant septicemic diseases responsible for mass mortality in freshwater fishes and consequently high economic losses. This study was carried out to investigate prevalence of Y.ruckeri among 0. niloticus and C. gariepinus at Dakahlia Governorate and to characterize the isolates phenotypically and genotypically in addition to detection of virulence genes (yrp,yrIIm,yhlA,yhlB,yrInv) in them by PCR assay and multi-drug resistance genes(blaTEM,qnrS,tetAgene). Therefore, (100) samples of O. niloticus and (100) samples of C. gariepinus collected from different localities at Dakahlia Governorate during the period fromApril 2019 to April 2020. Fish samples were subjected to clinical and postmortem examination then bacteriological examination from liver, kidney and spleen. The suspected isolates were characterized by cultural and morphological characters, some conventional biochemical tests and API 20E system then by PCR assay. 24 diseased fish were characterized as infected with Y.ruckeri [10 from O. niloticus (10%) and 14 from C. gariepinus (14%)] with 44 Y.ruckeri isolates with percentage of 22%. The phenotypic characterization of the isolates revealed that they were homogenous. Furthermore, 16SrRNA gene (specific common gene) was demonstrated in all Y.ruckeri isolates by PCR. Results of this study indicated that polymerase chain reaction is very reliable and rapid method for identification of Y.ruckeri isolates which may be helpful in prevention and control of yersiniosis. |