Prevalence of aeromonas hydrophila in oreochromis niloticus farms in Kafr El-Sheikh Governorate

الملخص EN

One hundred and Fifty six samples of Nile tilapia (Oreochromis niloticus), 53 samples from diseased and 103 samples from apparently healthy), were collected from different farms in different locality in Kafr Elsheikh Governorate, the samples were analysed for the prevalence of Aeromonas hydrophila over a period of nine months from first of December 2007 to end of Agusts 2008.

And for their anti-microbial resistance using the disk diffusion method.

Moreover the bacteria were tested for their pathogen city for fish and hemolytic activity.

The prevalence of Aeromonas hydrophila among Oreochromis niloticus were 6(35.3 %).There was a clear seasonality, as one isolates (1.3 %) were recovered in the winter months while five isolates (6.4 %) recovered in summer.

Despite the high level of homogeneity observed in strains of Aeromonas hydrophila in biochemical patterns, they displayed different degrees of virulence for Tilapia fish ; were 16.7 % strong virulent, 50 % virulent 16.7 %, weak virulent and 16.7 % avirulent by subcutaneous injection of Aeromonas hydrophila isolates.

All strains of Aeromonas hydrophila showed hemolytic activity on blood agar except one avirulant strains showing non hemolytic activity.

There is slight correlation was found between hemolytic activity and degree of virulence of the strains, also the isolates were tested against 13 antimicrobial agents and the result were , all the isolates were found 100 % resistant to Penicillin, Streptomycin, Polymyxin B, 95 % for Ampicillin and 70 % for Ciprofloxacin.All strains 100 % sensitive to Amikacin, Gentamicin, Nalidixic acid, Kanamycin, Neomycin, Tetracycline, and 90 % Chloramphenicol.