Isolation, identification of pathogenic bacteria from Ictalurus punctatus with fulminate septicemia
Large colonies with similar morphology and color were obtained from liver, spleen and kidney of channel catfish, Ictalurus punctatus with fulminate septicemia. The experiment was carried out with healthy juvenile channel catfish by means of injection with live 5 isolates randomly selected. All individuals of the fish injected died within 72 h. The symptom was similar to those of the naturally infected fish. Therefore, the isolates were suggested to be the pathogenic bacterium strain of Ictalurus punctatus with fulminate septicemia. These isolates were further identified as Bacillus cereus by phenotypic characters, analysis of their 16S rRNA and gyrB sequences. Antimicrobial sensitivity patterns of five strains were evaluated against 20 antimicrobial drugs. The result showed that they were all sensitive to seven quinolones, five aminoglycosides, midecamycin, clindamycin, novobiocin, and resistant to two cephalosporins and compound sulfamethoxazole.