Pathogenicity assay of probiotic-potential bacteria from the Kelabau fish (Osteochilus melanopleurus)

This study aimed to evaluate the pathogenicity of probiotic-potential bacteria from the gut of Kelabau fish (Osteochilus melanopleurus) collected from Melintang Lake, East Kalimantan Province, Indonesia. Common carp (Cyprinus carpió) juveniles were injected with 0.1 mL (106 CFU mL-1) bacterial suspension of BP1, BP3, BPs2, BK, Aeromonas hydrophila, and phosphate buffer saline, respectively. The injected fish were maintained in 20 L aquarium at a density of 10 individuals/aquarium for 7 days of experiment. Clinical sign, mortality, hematological parameters, histopathology of gills and kidney were observed. The ANOVA test showed that probiotic-potential bacteria from gut of Kelabau fish had a significant effect on the survival rate and hematological parameters of the C. carpio juveniles. The infected fish showed changes in clinical signs such as hemorrhage, edema, and ulcer. Histopathological analysis indicated gill hemorrhage, necrosis, hyperplasia, edema and epithelial lifting, kidney necrosis, melanosis and vacuolization in nephron tubular cells. BPs2 isolate provided the best survival rate of 93% and it is a safe option for C. carpio as a probiotic-potential bacteria.