Isolation and virulence characterization of Pseudomonas fluorescens isolated from symptomatic catfishes of sub-Himalayan region (original) (raw)

Occurrence of Bacterial Haemorrhagicsepticaemia (BHS) has been recorded in juvenile / mature Clarias batrachus during the summer months (April-July) of the years 2004-2006. The symptomatic fishes were exhibiting distended abdomen, haemorrhages, necrotization and ulceration on the general body surface, lethargic behaviour, low appetite, erosion of fins, swollen vents, presence of ascetic fluid in the abdomen and empty intestine filled with exudate fluid. Bacteriological examination revealed the appearance of colonies of Pseudomonas fluorescens (PF) in the form of convex / flat rounded with smooth edges and yellowish to fluorescent green on to agar medium. They proliferate at 30 ± 5 0 C temperature but did not develop at 45 0 C. Out of fifteen isolates PF4 was more virulent. Biochemical characterization of the PF isolates explicated that they were oxidative in nature, oxidase & catalase positive, gelatin, nitrate, arginin, and citrate degradative, mannitol, inositol, sorbitol and arbinose positive but lysine, ornithin, urease, H2S, indole and MR-VP responses negative. Experimental infection trial revealed 100% mortality in CB challenged with bacterial suspension (PF4) containing 6.1 x 10 5 , 6.1 x 10 4 , 6.1 x 10 3 cfu/ml and LD50 value of this isolate was enumerated to 6.1x10 3.5 cfu/ml fish-1 in case of CB.