الفهرس 
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Abstract
Aeromonas hydrophila and other motile aeromonads are among the most common bacteria in freshwater habitats throughout the world, and have been recognized as occasional pathogens of cultured and feral fishes.
A. hydrophila and other motile aeromonads are opportunistic pathogens causing haemorrhagic septicemia and ulcerative conditions, dropsy, exophthalmia, and fin and tail rot. These diseases are associated with high mortality and great economic losses in aquaculture (Rey et al., 2009). Aeromo¬nas spp., especially A. hydrophila is of wide spread in environment, aquaculture, domestic animals and foods. In human the organism causing disease spectrum varies from gastroenteritis, septicemia, traumatic and aquatic wound infection (Daskalov, 2006). Aquaculture production has more than tripled in the past 15 years and will contribute for about (39%) of total seafood (Sapkota et al., 2008). Of note, Tilapia market has been rapidly growing from family farming to intensive farming industry (Chuanchuen, 2011).
al Antimicrobial agents are of great value for devising curative measures against bacterial infections. But, progressively increasing resistance to these agents is a serious cause of concern and periodic monitoring of drug resistance of these organisms should be carried out in different geographical areas. Therefore, the appropriate antimicrobial can be chosen for empiric therapy (Kashkedikar and Chhabra, 2010). Antibiotic resistance continues to be a serious public health threat worldwide. Antibiotic resistance may be inherited or acquired due to selective pressure of antibiotics during which the bacteria mutate to overcome the antibacterial effect of the antibiotic; this mutant gene became as a fixed part of whole bacterial genomic structure (Zarb et., 2012). Multiple drug resistance is acquired non susceptibility to at least one agent in three or more antimicrobial categories. New ECDC (European Center for Disease Control) data have shown that there has been a considerable increase over the last four years of combined resistance to multiple antibiotics (Zarb et al., 2012).