Laboratory Diagnosis of Pathogenic Bacteria Vibrio harveyi by PCR Test and Its Bioremediation with Indigenous Probiotic Bacteria Lactobacillus spp

Abstract

The present study was conducted to diagnose Vibrio harveyi using PCR with its bioremediation applying indigenous probiotic (Lactobacillus spp.) of prawn body. For these purposes, 30 specimens of prawn sample (28.6 ± 0.1g, 12 ± 1cm) were collected from local market, Khulna. Vibrio harveyi and Lactobacillus spp. which were isolated to check antagonistic effect through in-vitro and in-vivo test. In in-vitro challenge test, the potential and significant (P<0.5) antagonistic effect of Lactobacillus spp. against Vibrio harveyi was gradually reduced at 0, 4ᵗʰ, 8ᵗʰ and 12ᵗʰ hour of probiotic inoculation. In in-vivo challenge test, fifty (50) fingerlings of prawn (1±0.2g, 0.45±0.02cm) were stocked in earthen ponds (70m x 70m x 1m). Larvae were fed twice per day with probiotic mixed feed for treatment group while no probiotic were given for control groups. The result indicated slow reduction of Vibrio harveyi up to 40 days where as significant (P<0.5) reduction was obtained at 50ᵗʰ and 60ᵗʰ days of experiment. The result showed that treatment groups have shown better performance rather than control groups in terms of growth, digestibility and immunity. Probiotic treated prawn achieved higher growth are these the achievements of probiotic treated groups based on final weight (16.49 ± 0.54), percentage weight gain (549. 30 ± 40.02) and specific growth rate (3.11 ± 0.10) than their counter control group while final weight (9.01 ± 0.36), percentage weight gain (310.77 ± 18.68) and specific growth rate (2.35 ± 0.08). Absorbance of protease (2.74 mg/ml) and amylase (1.23 mg/ml) were significantly higher (P<0.5) than the protease (1.82 mg/ml) and amylase (0.7 mg/ml) absorbance of control group. The result of this experiment indicated higher immunity of treatment group compared to control group. So, better growth, strong digestibility and powerful immunity of treatment group supports the use of probiotic mixed feed. The result also suggested that probiotic treatment can be an effective alternative to the use of antibiotics in treatments of bacterial diseases in prawn aquaculture.