Similarity of Tetracycline Resistance Genes Isolated from Fish Farm Bacteria to Those from Clinical Isolates

Abstract

ABSTRACT Tetracycline-resistant (Tet r ) bacteria were isolated from fishes collected at three different fish farms in the southern part of Japan in August and September 2000. Of the 66 Tet r gram-negative strains, 29 were identified as carrying tetB only. Four carried tetY , and another four carried tetD . Three strains carried tetC , two strains carried tetB and tetY , and one strain carried tetC and tetG . Sequence analyses indicated the identity in Tet r genes between the fish farm bacteria and clinical bacteria: 99.3 to 99.9% for tetB , 98.2 to 100% for tetC , 99.7 to 100% for tetD , 92.0 to 96.2% for tetG , and 97.1 to 100% for tetY . Eleven of the Tet r strains transferred Tet r genes by conjugation to Escherichia coli HB-101. All transconjugants were resistant to tetracycline, oxycycline, doxycycline, and minocycline. The donors included strains of Photobacterium , Vibrio , Pseudomonas , Alteromonas , Citrobacter , and Salmonella spp., and they transferred tetB , tetY , or tetD to the recipients. Because NaCl enhanced their growth, these Tet r strains, except for the Pseudomonas , Citrobacter , and Salmonella strains, were recognized as marine bacteria. Our results suggest that tet genes from fish farm bacteria have the same origins as those from clinical strains.