Bacillary necrosis occurs very often in intensive farming of Tra catfish (Pangasius hypophthalmus) in the Mekong delta. Causative bacterium was identified as Edwardsiella ictaluri. Diseased fish with typical focal necrosis in the liver, kidney and spleen were sampled from 17 fish farms in Can Tho, Dong Thap, Vinh Long, An Giang and Ben Tre Province for bacterial isolation and identification. Among 97 isolates, 47 (48 %) were identified as E. ictaluri. Bacterial strains were tested for the resistance to six kinds of antibiotic as Sulfamethoxazole/Trimethoprim (SXT), Amoxycillin (AML), Doxycycline (DX), colistin (CLT), Oxytetracycline (OT) and Florfenicol (FFC). All 47 strains resisted to SXT and 46 (97,8 %) to CLT. Numbers (percentages) of strains showed different levels. | NGHIÊN CỨU KHOA HOC KY THUAT 175 PHAN LẬP VA khao sat DẬC DIEM KHANG KHANG SINH CUA Edwardsiella ictaluriGAY BỆNH GAN THẬN MU TREN CA TRA Pangasius hypophthalmus NUOi THẬM canh ISOLATION AND INVESTGATION FOR ANTIBIOTIC RESISTANCE OF Edwardsiella ictaluri FROM INTENSIVELY FARMED TRA CATFISH Pangasius Hypophthalmus Nguyen Hữu Thịnh Trương Thanh Loan Khoa Thuy San Đại hoc Nong Lam thanh pho Ho Chí Minh E-mail thinhfishery@ Bo mon Cong Nghe Sinh Hoc Đai hoc Nong Lam thanh pho Ho Chí Minh ABSTRACT Bacillary necrosis occurs very often in intensive farming of Tra catfish Pangasius hypophthalmus in the Mekong delta. Causative bacterium was identified as Edwardsiella ictaluri. Diseased fish with typical focal necrosis in the liver kidney and spleen were sampled from 17 fish farms in Can Tho Dong Thap Vinh Long An Giang and Ben Tre Province for bacterial isolation and identification. Among 97 isolates 47 48 were identified as E. ictaluri. Bacterial strains were tested for the resistance to six kinds of antibiotic as Sulfamethoxazole Trimethoprim SXT Amoxycillin AML Doxycycline DX colistin CLT Oxytetracycline OT and Florfenicol FFC . All 47 strains resisted to SXT and 46 97 8 to CLT. Numbers percentages of strains showed different levels of resistantce to FFC AML OT and DX which were 20 42 5 19 40 4 15 31 9 and 13 27 7 respectively. The results of this study suggest that appropriate use of antibiotic for treatment of the disease should rely on tested antibiograms to isolates. ĐẠT VÂN ĐÊ Edwardsiella ictaluri trực khuẩn Gram am la nguyen nhan gay bệnh viếm ruột mhiem khuấn huyết tren ca nheo Ictalurus punctatus tai Hoa Ky. Vi khuấn lan đầu tiến đựợc phan lập va định danh vao nam 1976 Hawke 1979 . Tựđo đến nay vi khuấn luon đựợc xem la nguyen nhan gay bếnh vôi ty le chết rất cao trến ca nheo nuoi cong nghiếp. Nghe nuoi ca tra Pangasius hypophthalmus tham canh tai nựỢc ta phat triển rất nhanh trong 10 nam trô lai đay. San lựợng ca tra nuoi ựỢc đat 800 ngan tấn vao nam .
