Optimum dose of gamma irradiation to inactivate Vibrio paraheamolyticus in fresh and freeze-dried

Vibrio paraheamoloyticus is one the causative agents of vibriosis with high mortality in farmed fish and shrimp and under predisposing conditions. This study was aimed to assess the effect of gamma irradiation on the inactivation of V. paraheamoloyticus under fresh and freeze-dried conditions. Vials of 0.5 ml fresh culture of the bacterial suspensions at 1.5*1010 cfu/ml were subjected to 1, 1.5,2, 2.5, 3 and 4 KGy. Also, vials of 0.5 ml freeze-dried culture of the bacterial suspensions at 1.5 x 1010 cfu/ml were subjected to 2, 4, 7 and 8 KGy. The bacterial growth behavior was then evaluated on fresh medium. The obtained results showed that the minimum doses of 4 and 10 KGy were sufficient for the inactivation of fresh and freeze-dried bacteria, respectively. The result of this study shows that inactivation of V. paraheamolyicus in fresh culture condition requires below half- dosage of gamma ray required for the inactivation of the freeze- dried of bacterial cells.