Abstract: To evaluate Aeromonas hydrophila in the status of drug resistance to florfenicol which was the major pathogen from freshwater fish, we tested resistance to florfenicol of 26 strains of Aeromonas hydrophila collected from freshwater fish in Beijing area nearly three years using disk diffusion method and concentration dilution method, respectively. Then, we detected the florfenicol resistance gene of strains using PCR method. The results showed that 15.38% of stains were resistant to florfenicol. The minimum inhibitory concentration of florfenicol to strains was mainly 2 to 4 μg/mL presently, and 5 strains were more than 8 μg/mL. Florfenicol resistance gene floR was detected in 1 strain. Combined with previous data and the relative data of other provinces, it was obvious that the florfenicol resistance rate and resistance concentration of Aeromonas hydrophila were both higher than before, and the strains carried floR gene located in plasmid on the risk of transferring the gene to other species of fish pathogens. Therefore, it was necessary to use florfenicol scientifically in aquaculture.

Key words:

Aeromonas hydrophila; florfenicol; resistance; floR gene