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 Tabriz city.50 samples from 5 Reared Oncorhynchus mykiss farms in Tabriz city (For each farm,10 numbers) were randomly assigned to suspected fish to the disease. By using biochemical tests, 14 samples (28%) from 2 Fish farms (40%) were identified as A.hydrophila. Antibiogram for these specimens showed that the bacterium had the highest resistance tovancomycin (100 %) and clindamycin (92.8%) antibiotics, and has the most sensitivity to the antibiotics ofsultrim, tetracycline and oxytetracycline with 71.4%.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.

Indiscriminate use of antibiotics in poultry farms increases the chance of antibiotic resistant and extended-spectrum β-lactamase (ESBL) producing bacteria in Bangladesh. Therefore, the study was under taken to detect ESBL producing Escherichia coli (E. coli) in chickens. Materials and methods: A total of 60 cloacal swab samples (20 from commercial layer, 20 from commercial broiler and 20 from commercial sonali chickens) were collected from Rajshahi district of Bangladesh. The E. coli was isolated from these samples and identified based on cultural, staining, and biochemical characteristics. The disk diffusion method was used to assay the antibiotic resistant/sensitivity patterns of the isolated E. coli. Phenotypc detection of ESBL producing E. coli was also done.The prevalence of E. coli in chickens was 61.67% in Rajshahi district of Bangladesh, where the prevalence was 60%, 60%, and 65% in commercial layer, commercial broiler, and commercial sonali chickens, respectively. The antibiotic sensitivity assay of E. coli isolated from commercial layer chickens showed 100%, 80%, 50%, 40%, and 40% resistant to amoxicillin, tetracycline, cefotaxime, ciprofloxacin, and ceftazidime, respectively. E. coli isolated from commercial broiler chickens showed 100%, 100%, 60%, 50%, and 40% resistant to amoxicillin, tetracycline, cefotaxime, ceftazidime, and ciprofloxacin, respectively. E. coli isolated from commercial sonali chickens showed 90%, 70%, 50%, 50%, and 40% resistant to amoxicillin, tetracycline, cefotaxime, ciprofloxacin, and ceftazidime, respectively. In phenotypic detection, the overall prevalence of ESBL producing E. coli was 43.33%, where 40%, 50%, and 40% in the commercial layer, commercial broiler, and commercial sonali chickens, respectively in Rajshahi district of Bangladesh.These results indicated that chickens are a potential reservoir for ESBL producing E. coli and their antibiotic resistances are obviously significant. These findings will help us to make proper guideline for the treatment, prevention and control of E. coli prevalent in chickens in Bangladesh.