Detection of the staphylococcal multiresistance gene cfr in Escherichia coli of domestic-animal origin.

OBJECTIVES: To investigate the presence and the genetic environment of the multiresistance gene cfr in Escherichia coli found in domestic animals.

METHODS: A total of 1230 E. coli isolates, collected from pigs, chickens and ducks, were screened by PCR for the cfr gene. The location of the cfr gene was determined by Southern blotting, the transferability of cfr gene was tested by conjugation and transformation, and the regions flanking the cfr gene were sequenced by a modified random primer walking strategy. The location of the cfr promoter sequence was analysed by mapping the cfr transcription start site using rapid amplification of 5' cDNA ends (5' RACE).

RESULTS: Only a single strain from the nasal swab of a pig harboured the cfr gene. Southern blotting indicated that the cfr gene was located on a ~110 kb plasmid, designated pEC-01. A cfr-carrying segment of 1545 bp with a sequence identical to that of the cfr-harbouring plasmid pSCFS1 was flanked by two IS26 elements in the same orientation. The IS26 transposition created a new hybrid promoter in which the -35 region was part of the left inverted repeat of IS26 while the -10-like sequence was part of the original cfr upstream region.

CONCLUSIONS: To the best of our knowledge, this is the first report of the cfr gene in a naturally occurring E. coli strain. Continued surveillance of the presence of the cfr gene in Gram-negative bacteria of domestic-animal origin is warranted.