الفهرس | Only 14 pages are availabe for public view |
Abstract In this study, 93 diseased O. niloticus and 87 diseased C. gariepinus were collected from different localities in Sohag Governorate during the period from March 2014 to March 2015. The samples were subjected to clinical and post-mortem examination then for bacteriological examination from liver, kidney and spleen. The suspected isolates were characterized by cultural and morphological characters, biochemical tests including API 20E assay then by PCR assay in addition to studying their haemagglutinating activity and haemolysin production in vitro and examination of E. tarda and Y. ruckeri isolates for presence of major fimbrial subunit gene (etfA) and protease gene (yrp1) respectively by PCR assay. 9 isolates were characterized as E. tarda [4 isolates (E1-E4) from O. niloticus (4.3%) and 5 isolates (E5-E9) from C. gariepinus (5.7%)] and 5 isolates were characterized as Y. ruckeri [3 isolates (Y1-Y3) from O. niloticus (3.2%) and 2 isolates (Y4-Y5) from C. gariepinus (2.3%)]. The phenotypic characterization of E. tarda isolates revealed that the isolates were homogenous except for citrate utilization, the similarity between them was ranged from 96.3 to 100% and they were typical strains of E. tarda. On the other hand, the phenotypic characterization of Y. ruckeri isolates revealed that the isolates were homogenous except for Voges-Proskauer and gelatine liquifaction tests, the similarity between them was ranged from 92.9 to 100% and they belonged to Biotype 1 of Y. ruckeri. Based on results of Voges-Proskauer and gelatine liquifaction tests, Y. ruckeri isolates could be grouped into three biochemical traits. PCR assay revealed that all E. tarda isolates had major fimbrial subunit gene (etfA) and all Y. ruckeri isolates had protease gene (yrp1) which proved their pathogenicity. |