Anti bacterial activity of plant extracts against antibiotic resistant Vibrio species isolated from water and post larvae samples of P. monodon

Objective: The present investigation was carried out to determine the Vibrio load of water and post-larvae of Penaeus monodon and their resistance to different antibiotics used commonly in aquaculture, and also to determine the efficacy of plant extracts on them. Method & Materials: The samples used for this experimental analysis were obtained from two shrimp hatcheries. TCBS and Zobell Marine were used in the Microbiological analysis. Antimicrobial sensitivity tests were conducted on bacterial isolates from water and post-larvae of P. monodon using the disc diffusion method. Water extract of Terminalia arjuna and T. bellerica were prepared by crushing and soaking the edible part of the seeds (1g) in distilled water (100ml) for 48 h. The minimum inhibitory concentration (MIC) of plant extracts against the bacteria isolated from water and post larvae of P. monodon were determined by the micro dilution techniques. Results & Conclusion: The total number of bacterial flora from water samples was estimated on Zobell marine agar and thiosulphate citrate bile salt agar (TCBS). The total numbers of bacteria were found to vary between the rearing tanks of the two hatcheries. The number of colony forming units per ml is ranged from 0.2 X 102± 0.1 to 7.3 X 102±0.9 in one hatchery. In another hatchery in reared water the number of colony forming units per ml was 0.3 X 102± 0.1 to 8.2 X 102± 0.6. Samples of luminescent bacterial colonies were frequently noted. A total of 320 bacterial isolates from water and post larvae samples were examined for their resistance to five antibiotics. The highest percentage of bacterial species were found to be resistant to Erythromycin, Ciprofloxacin & Gentamycin. 81% of the bacterial isolates were resistant to Norfloxacin, and 75% of bacterial isolates were resistant to Nitrofurantoin. The MIC values plant extracts against Vibrio species were tested. The growth of all bacterial isolates were inhibited with T. bellerica at 100μg/ml, but T. arjuna at 150 μg /ml, respectively.

Keywords:

Antibacterial activity , plant extracts , resistant Vibrio species , Penaeus monodon