Diversity of Tn <i>1546-</i> Like Elements in Vancomycin-Resistant Enterococci Isolated from Humans and Poultry in Korea

Abstract

To investigate the possible spread of vancomycin resistance among enterococci through horizontal gene transfer between two sources of vancomycin-resistant enterococci (VRE) isolated from farm animals and humans in Korea, molecular characterization of VRE isolated from poultry (20 isolates) and humans (35 isolates) was performed by PCR-restriction fragment length polymorphism typing of the vanA gene cluster (Tn1546). PCR mapping of Tn1546 finally distinguished seven different transposon types (types A to G). Type A was observed only in the poultry isolates, while the other six types were present only in the human isolates. An insertion sequence and deleted sequence were detected in most of the human isolates in the orf2-vanR and vanX-vanY regions in the Tn1546-like element, but not in the poultry isolates. Tn1546-like elements were found in conjugal plasmids of most human VRE, whereas they were detected in the chromosomes of all poultry VRE. Accordingly, no evidence was found of any recent transmission of vancomycin resistance genes between poultry and humans in Korea.