Aeromonas hydrophila is a gram-negative, positive
oxidase, anaerobic, and opportunistic bacteria that, under certain conditions, become a pathogen (in humans and fish). This bacterium causes toxin and host infection in which different antibiotic resistance in isolated strains has been reported in different regions of the world. The aim of this study was to determine the prevalence of this bacterium and its susceptibility to common antibiotics in Marand city. 30 fish from 3 Reared Oncorhynchus mykiss
in Marand (For each farm, 10 numbers) were randomly assigned to suspected fish to the disease. By using biochemical tests, 9 samples were identified as Aeromonas hydrophila. Antibiogram for these specimens showed that the bacterium had the highest resistance to vancomycin (88.9%) and clindamycin (77.8%) antibiotics. Considering the different antibiotic resistance pattern in this study and other similar studies, the necessity of examining the pattern of resistance in each region seems necessary.
