Virulence of Pseudomonas and Aeromonas bacteria isolated from Anabas sp from Lal Dighi, Paschim Medinipur, West Bengal

The significance of Aeromonas and Pseudomonas bacteria in association with out breaks of diseases in feral and aquaculture fish production is of paramount important. Seven isolates of Aeromonas hydrophila(4) A.voronii(2) and Pseudomonas aeroginosa(1) isolated from normal and ulcer affected Anabas sp in Lal Dighi were examined for virulence. Invitro experiment was conducted in 10 disinfected 30L glass aquaria filled with chlorine free water. 300 healthy Anabas sp (60-100gm) were used in which 30 fishes were stocked in each aquarium. Two aquaria stocked with 20 fishes each were used control. The fishes were acclimatized for 19 days prior to the infection experiment. Each fish except the control intramuscularly injected with 0.1 ml of the experimental bacteria (concentration, 2.3×108 CFU/ml) using 21/guage sterile needle. The infected fishes were observed for 19 days. The injected bacteria were then isolated from the experimental fishes and subjected to morphological, biochemical and antibiotic susceptibility tests. Result showed that;120 out of 190 infected fishes developed clinical abnormalities such as skin darkness, scales detachment, blindness and large irregular haemorrhage on the body surface,fin necrosis,exophthalmia and eye cataract/trachoma within four days and mortality rate of 97%. The isolated strains were motile,gram(−ve) and were resistant to Ampicillin, Streptomycin, Amoxyllin and novobiocin. This study concluded that Aeromonas and Pseudomonas species are responsible for the out break of ulcerative diseases in Lal Dighi.