The present study was conducted on 225 diseased fish samples, 125 Nile tilapia (Oreochromis niloticus) and 100 Cat fish(Claris gariepinus) , collected from different fish markets at Kaliobia Governorate during the period from January (2016) to May (2017) for inspection of Aeromonas strains. Samples were collected from apparently pathognomic lesions in muscle, kidney, liver, intestine and spleen after clinical and postmortem examination for bacteriological examination. The results revealed that, 125 Aeromonas species were isolated from examined samples where A. hydrophila and A. caviae were the only species isolated. 114 (91.2 %) A. hydrophila strains, 63 (50.4%) and 51 (40.8%) were isolated from C. gariepinus and O. niloticus fishes respectively. Meanwhile, 11(8.8 %) A. caviae strains, 7 (5.6%) and 4 (3.2%) from C. gariepinus and O. niloticus fishes respectively. Aeromonas strains were highly resistant for ampicillin; methicillin; penicillin-G; vancomycin; oxacillin; amoxicillin, cefotaxime; oxytetracycline; erythromycin and streptomycin. Meanwhile, ciprofloxacin, enrofloxacin, gentamicin, and florphenicol were the most proper antibiotics with the highest in vitro efficiency against them. PCR results for antibiotic resistant genes in isolated Aeromonas strains showed that, they were detected in most studied strains, where, blaTEM gene was detected in all 10 A .hydrophila studied strains and in 5 out of 6 A. caviae; tetA(A) gene in 9 out of 10 A .hydrophila and in 5 out of 6 A. caviae; sul1 gene in 8 out of 10 A .hydrophila and in 4 out of 6 A. caviae and aadA1gene in 7 out of 10 A .hydrophila and in 3 out of 6 A. caviae.
Key words: Fish, bacteriological evaluation, Aeromonas species, antibiotic resistant genes