Aims: This study used restriction fragment length polymorphism (RFLP) with Aeromonas‐specific primers to identify species of Aeromonas and to investigate their distribution in a trout farm and stream. Methods and Results: In January, May, August and November 2000, presumptive Aeromonas species were recovered from a farm and a sedimentation pond in a fish farm and stream, and identified by PCR‐RFLP analysis with Aeromonas‐specific primers. The specificity of Aeromonas‐specific primers and the suitability of PCR‐RFLP analysis for identifying Aeromonas spp. were confirmed with fatty acid methyl esters (FAMEs) and 16S rDNA sequencing analyses, respectively. Levels of Aeromonas spp. sampled in May and August were higher than in January and November at all sampling sites. Aeromonas salmonicida was the dominant species in January and November, and the proportion of pathogenic species (Aer. hydrophila, Aer. caviae and Aer. veronii) increased in May and August. Conclusions: PCR‐RFLP analysis with Aeromonas‐specific primers is a rapid and reliable method for identifying widely distributed Aeromonas spp. from environmental samples. Significance and Impact of the Study: To minimize human health risk, monitoring the levels and species composition of Aeromonas in fish farm is advisable.

No abstract