Isolation and Antibiotic Susceptibility of Aeromonas spp. From Freshwater Fish Farm and Farmed Carp (Dam of 16 Tishreen, Lattakia)

A total of 30 water samples and 45 infected fish (carp, Cyprinus carpio) were collected from freshwater fish farm (Dam of 16 Tishreen-Lattakia) and analysed bacteriological. Macroscopic examinations of infected fish had showed the presence of haemorrhagic skin lesions with brown or red spots throughout their skin. A total of 64 Aeromonas strains were isolated. The Aeromonas isolates were distributed as follows: Aeromonas hydrophila (34, 53%), A. caviae (16, 25%), A. sobria (9, 14%) and (5, 8%) of unidentified aeromonads. Collectively, Aeromonas spp. are considered as opportunistic causative agents of human gastroenteritis and other infections. Antibiotic susceptibility tests were carried on all strains of isolated Aeromonas spp. using twenty different antibiotics by agar disk diffusion method. The majority of Aeromonas spp. strains was found to be completely resistant to penicillin, ampicillin with high levels of resistance ( 75%) to streptomycin, amoxicillin and novobiocin. Approximately 65% of the tested strains showed resistance to oxytetracycline. Around half of the tested strains was resistance to tetracycline (53%), cephalothin (52%) and erythromycin (50%). Variable responses were observed towards the antibiotics nalidixic acid, colistin, and chloramphenicol and the resistance levels were 30, 17 and 12% respectively. Resistances to gentamicin, amikacin and kanamycin appeared in less than 8% of the studied strains. All studied strains of Aeromonas spp. were susceptible to the antibiotics ciprofloxacin, trimethoprim- sulphamethoxazole, lincomycin, cefixime and neomycin. No significant difference was found in antibiotic responses among strains isolated from water or fish.