الفهرس 
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Abstract
The isolation of highly virulent strains of Aeromonas and particularly A. hydrophila had been increasing during the past few years; thus these bacteria can not longer be classified among the ”opportunistic” agents and ecological relationship between Aeromonas, man, environment and animal had aroused increased interest in both human and veterinary fields.
Sharkia Governorate was the scope of the current study to update information about incidence of Aeromonas spp. in a variety of food types especially fish, milk, meat and sauage.
Results revealed highest incidence (55%) in milk samples followed by Tilapia nilotica (Oreochromis niloticus) (48.57%) and meat samples (40%). Isolated Aeromonas spp. were identified following Bergey’s manual using API 20 E system , as A. hydrophila gr.1 and gr.2, A. salmonicida and A. caviae. A. hydrophila dominated other species (13 isolates out of 19) especially in milk and Tilapia nilotica (Oreochromis niloticus). Isolated Aeromonas spp. possessed multiple virulence factors, thus have the potential to be pathogenic. Protease and lecithinase enzymes were detected in all examined Aeromonas spp., while hemolysin was detected in A. hydrophila and A. salmonicida only. Using PCR technique, act and alt entertoxins genes were detected in the three tested species.
Using biotic agents to control A. hydrophila in vitro confirmed efficiency of onion juice (1% v/v) to reduce initial counts by about one log cycle, garlic juice reduced count by more than one log cycle and garlic oil completely inhibited viable cells after 96 h incubation. Similarly, cell free supernatant fluids of 4 tested LAB (L. delbreukii ssp. bulgaricus, L. lactis ssp. lactis, Enterococcus faecium, L. plantarum) completely inhibited viable cells of tested A. hydrophila after 72 h.
In conclusion, PCR technology could have an important role in assessing Aeromonas influences on adverse public health issues. Also, biotic agents including plant sources and probiotics might have significant role in disease control and food preservation strategies.