<![CDATA[This research is to isolate, identify and know the pathogenicity of Aeromonas sp . originating from African catfish in Ngawi Regency. Fish that had symptoms of illness and were 20 - 25 cm in size obtained from rearing ponds in 3 sub-districts were used as research samples. Fish kidneys were used for bacterial isolation and inoculated using GSP medium. Furthermore, the characterization and identification of bacteria was carried out by observing the colony morphology, cells, and biochemical properties. Furthermore, Koch's Postulate test was carried out which aims to prove the nature of the pathogen. Furthermore, catfish seeds measuring 7 - 9 cm were measured with a Lethal Dosage of 50 to determine their level of pathogenicity. The results showed that fish were infected with bacteria, where symptoms appeared, namely the skin had ulcers, damage to the kidneys and swelling of the stomach. A total of 15 bacterial isolates obtained consisted of six from Geneng District, five from Karang Jati District and four isolates from Paron District. The identification results showed that Aeromonas hydrophila was identified from 12 isolates, A. salmonicida was identified from three isolates. Isolates A. hydrophila GKJ1, GKJ4, GGN2, GGN5, GPR2 and GPR4 were virulent against these fish.INTISARI Penelitian ini untuk mengisolasi, mengidentifikasi dan mengetahui patogenitias bakteri Aeromonas sp . yang berasal dari lele dumbo di Kabupaten Ngawi. Ikan yang memiliki gejala sakit dan berukuran 20 - 25 cm yang diperoleh dari kolam pembesaran di 3 kecamatan digunakan untuk sampel penelitian. Ginjal ikan digunakan untuk isolasi bakteri dan diinokulasikan menggunakan medium GSP. Selanjutnya dilakukan karakterisasi dan identifikasi bakteri dengan mengamati morfologi koloni, sel, dan sifat biokimia. Selanjutnya dilakukan uji Postulat Koch yang bertujuan untu membuktikan sifat patogen. Selanjutnya benih lele yang berukuran 7 - 9 cm diukur nilai Lethal Dosage 50 untuk mengetahui tingkat patogenitasnya. Hasil menunjukkan ikan terinfeksi bakteri, dimana munculnya gejala yaitu bagian kulit terdapat luka borok, kerusakan pada ginjal dan perut mengalami pembekakan. Total isolasi bakteri yang didapat sebanyak 15 yang terdiri dari enam berasal dari Kecamatan Geneng, lima berasal dari Kecamatan Karang Jati dan empat isolate berasal dari Kecamatan Paron. Hasil identifikasi menunjukkan bahwa bakteri Aeromonas hydrophila teridentifikasi dari 12 isolat, bakteri A. salmonicida teridentifikasi dari tiga isolate. Isolat A. hydrophila GKJ1, GKJ4, GGN2, GGN5, GPR2 dan GPR4 bersifat virulen terhadap ikan tersebut.pathogenicity ]]>
