Isolation of Bdellovibrio as Biological Therapeutic Agents Used For the Treatment of Aeromonas hydrophila Infection in Fish

Authors


W.-H. Chu. No. 24, Tongjiaxiang, Department of Microbiology, School of Life Science & Technology, China Pharmaceutical University, Nanjing 210009, China. Tel./Fax: 086 25 83271323; E-mail: churong@yahoo.cn

Summary

Fourteen strains of Bdellovibrio-like organisms were isolated from cultured fish ponds using Aeromonas hydrophila J-1 as host, one of them formed large plaques after 48 h of incubation at 28°C on a double layer plate, designated as Bdellovibrio C-1. The Bdellovibrio was confirmed by electron microscopy and PCR amplification of Bdellovibrio-specific 16S rDNA. The optimum temperature for the growth of BdC-1 was between 15–37°C and with optimal activity at temperatures of 25–30°C. The ability of BdC-1 to lyse A. hydrophila was similar in the pH range of 6.5 to 8.5. It can lyse 23 Gram-negative bacterial strains comprising three genera of fish pathogens and one strain of Escherichia coli but cannot lyse Gram-positive bacteria such as Bacillus subtillis and Staphylococcus aureus. Immersion of fish in water containing different concentrations of BdC-1 was used in protection against an experimental infection of A. hydrophila J-1. Results show that the mortality of groups immersed with BdC-1 was lower than the group without BdC-1. These results suggest that it may be possible to use Bdellovibrio to control the disease caused by A. hydrophila.

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