Objectives: To characterize the Tn1546 structure and to perform the genetic typing of 51 PFGE-unrelated vanA-containing enterococci of different origin (clinical, food and faecal samples of healthy humans and healthy poultry).
Methods: Tn1546 structure was characterized by a PCR primer walking strategy and sequencing. Multilocus sequence typing (MLST) was performed for Enterococcus faecium and Enterococcus faecalis strains, and esp and hyl genes were detected by PCR.
Results: Nine different Tn1546 structures were identified in the studied strains. Type I was the most prevalent structure (75%) (identical to GenBank M97297). Two new Tn1546 structures were identified (in three clinical and animal strains), containing two new insertion sequences (ISs; ISEfa11 disrupting vanS and ISEfa10 disrupting orf1). An additional new Tn1546 structure was found in one animal strain, containing ISEf1 interrupting vanY and IS1542 in the orf2-vanR region. A high diversity of sequence types (STs) was detected among clinical (6 ST/18 strains) and non-clinical E. faecium strains (18 ST/24 strains). STs associated with clonal complexes CC17 and CC9 were mainly detected among clinical and non-clinical E. faecium strains, respectively. Seven new STs were identified in non-clinical strains. The esp and hyl genes were only found among clinical E. faecium strains.
Conclusions: A moderate variability in Tn1546 structure has been detected among unrelated vanA-containing enterococci of different origins, showing three new structures including two new ISs. A high diversity of STs was detected among E. faecium strains, especially among non-clinical strains, and new STs have been identified.