ISOLATION OF Aeromonas BACTERIOPHAGE AvF07 FROM FISH AND ITS APPLICATION FOR BIOLOGICAL CONTROL OF MULTIDRUG RESISTANT LOCAL Aeromonas veronii AFs2

Aeromonas isolates from Nile tilapia fish, fish ponds and River water were identified as well as their bacteriophage specific. Also evaluation of antibacterial effect of both nanoparticles and phage therapy against the pathogenic Aeromonas veronii AFs2. Differentiation of Aeromonas spp. was done on the basis of 25 different biochemical tests and confirmed by sequencing of 16s rRNA gene as (A. caviae AFg, A. encheleia AWz, A. molluscorum AFm, A. salmonicida AWh, A. veronii AFs2, A. veronii bv. veronii AFi). All of the six Aeromonas strains were resistant to β-actam (amoxicillin/ lavulanic acid) antibiotics. However, the resistance to other antibiotics was variable. All Aeromonas strains were found to be resistant to ampicillin, cephalexin, cephradine, amoxicillin/clavulanic acid, rifampin and cephalothin. Sensitivity of 6 Aeromonas strains raised against 7 concentrations of chitosan nanoparticles. Using well diffusion method spherically shaped silver nanoparticles AgNPs with an average size of ~ 20 nm, showed a great antimicrobial activity against A. veronii AFs2 and five more strains of Aeromonas spp. At the concentration of 20, 24, 32 and 40 µg/ml. Thermal inactivation point was 84oC for phage AvF07 which was sensitive to storage at 4oC compared with the storage at -20oC. Intraperitoneal injection in fish using phage AvF07 together with A. veronii AFs2, no mortality was shown until the end of experiment (14 days). However, mortality of 43.8% or 50% was obtained after 2 or 3 days, respectively, when chloramphenicol was injected instead of phage.