Abstract: To understand the prevalence and genetic diversity of Escherichia coli (E. coli) in the dairy farm environment and explore the genetic relationships of isolates from different samples, we conducted this experiment. In this study, E. coli was isolated from 209 samples which collected from a dairy farm environment in 2017-2019 and identified by 16S rRNA gene. The ERIC-PCR genotyping and phylogenetic grouping were performed respectively with non-duplicate E. coli. Three hundred and thirty-eight E. coli strains were isolated and the isolation rate was 67.46%. The E. coli was clustered into 14 types by ERIC-PCR genotyping. Type Ⅳ was the dominant, including 196 strains, followed by type Ⅰ (59 strains), type Ⅴ (31 strains) and type Ⅹ (11 strains). The remaining 41 strains were distributed in the other 10 types. The phylogenetic grouping results showed that 2 strains were not classified. The rest were classified into 6 types and the most strains were in group B1 (75.45%). The proportion of group A,C,E,D and F were 18.34%, 2.96%, 1.18%, 1.18% and 0.30%, respectively. E. coli had a wide range of DNA diversity in the dairy farm environment, and there was a close relationship between the strains from samples of different sources at different time. The phylogenetic grouping was mainly B1 group.

Key words: Escherichia coli, dairy farm environment, ERIC-PCR, phylogenetic grouping