Abstract: In order to investigate the distribution of Florfenicol resistance gene floR in pathogenic E. coli isolates from ducks, the PCR method was used to detect the floR in 20 duck-origin E.coli isolates which showed resistance to Florfenicol. As a result, all 20 isolates are floR positive and a PCR fragment with predicted size of 753 bp was obtained. For confirmation and phylogenetic analysis, floR genes from 2 strains were sequenced. The results demonstrated that the homology between two strains was 99.6%, while different homology (84.8% to 99.9%) with floR genes from cattle-and chicken-origin E.coli could be obtained. The phylogenetic analysis showed two floR sequences from duck-origin E.coli present a relatively low relationship. This suggested that there is no relationship between floR sequences and hosts origin of E.coli.

Key words: duck; pathogenic E. coli; Florfenicol; floR gene; cloning and sequencing