Studies on The Antibacterial Activity of Some Free and Entrapped Bacteriophages against Fish Pathogens

THREE DIFFERENT bacteriophages namely VPS1, APS2 and APS3 were isolated from crab (Callinectes sapidus), clams (Tapes decussatns) and fish (Tilapia sp.) samples. They belong to families Siphoviridae, Myoviridae and Podoviridae, respectively. Statistical analysis based on analysis of phages DNA by using random amplification of polymorphic DNA-polymerase chain reaction (RAPD-PCR) revealed that the similarity levels were different among the three phages. Entrapment of VPS1 and APS2 was carried out into calcium alginate beads. The antibacterial activity of VPS1 and APS2 were tested before and after entrapment in Ca-alginate beads against some fish pathogenic bacteria such as Vibrio anguillarum and Aeromonas hydrophila. VPS1 seeded beads were superior (significant at P<0.05) from the free phages in the reduction of the growth rate of V. anguillarum while, APS2 seeded beads exhibited lower efficiency in the reduction of A. hydrophila growth rate. Antibacterial activity of entrapped VPS1 was studied during 7 successive cycles. VPS1 was successful (significant at P<0.05) in the reduction of V. anguillarum growth rate. A successful trial showed the good applicability of entrapped VPS1 in reduction of 97% of the pathogenic Vibrio spp. in the water sample from El-Mex fish farm after 3 h. Chemical characterization of plain and phage seeded beads was performed by using Fourier transform infrared spectroscopy (FTIR).