A total of 150 fish samples, including 75 samples each of Tilapia nilotica and Mugil cephalus collected from different fish markets distributed in Mansoura city, Egypt were examined bacteriologically to determine the prevalence, antimicrobial susceptibility and the virulence of Aeromonas hydrophila regarding to aerolysin and haemolysin toxins using PCR technique. Phenotypically, presumptive A. hydrophila could be detected in 43/75 (57.33%) and 38/75 (50.67%) of the examined Tilapia nilotica and Mugil cephalus, respectively, with an overall incidence of 81/150 (54%). The results of PCR test based on using A. hydrophila 16S rRNA gene demonstrated that 32/75 (42.67%) and 29/75 (38.67%) of the examined Tilapia nilotica and Mugil cephalus, respectively were contaminated with A. hydrophila, with an overall incidence of 61/150 (40.67%). The aerA gene was detected in all (61) A. hydrophila strains, while hlyA gene couldn't detected in any of the identified strains. The results of antimicrobial susceptibility test showed that all (100%) isolated A. hydrophila strain were resistant to both ampicillin and carbenicillin, while chloramphenicol and amikacin showed the same percentage but account for sensitivity, whereas higher percentage of sensitivity was detected against ciprofloxacin (92.59%), followed by cefoxitin (87.65%), cefotaxime (80.24%), trimethoprim/sulfamethoxazole (79%), tetracycline (74%). The result declared that examined fish samples were markedly contaminated with virulent and multidrug strains of A. hydrophila which may be of a potential health risk.
Key words: A. hydrophila, virulent genes, fishes, PCR, antibiotics resistance
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