Tn 6674 Is a Novel Enterococcal optrA-Carrying Multiresistance Transposon of the Tn 554 Family

Abstract

The novel 12,932-bp nonconjugative multiresistance transposon Tn6674 was identified in the chromosomal DNA of a porcine Enterococcus faecalis strain. Tn6674 belongs to the Tn554 family of transposons. It shares the same arrangement of the transposase genes tnpA, tnpB, and tnpC with Tn554 However, in addition to the Tn554-associated resistance genes spc and erm(A), Tn6674 harbored the resistance genes fexA and optrA Circular forms of Tn6674 were detected and suggest the functional activity of this transposon.

Keywords: Enterococcus faecalis; optrA; oxazolidinones; phenicols; transposon.

FIG 1

Structural comparison of E. faecalis transposon Tn6674 with other related Tn554 family transposons. Accession numbers are as follows: Tn554, X03216; Tn5406, AF186237; Tn558, AJ715531; Tn559, FN677369; Tn6133, FR772051; Tn6188, HF565366; Tn6260, KX470419; and Tn6674, MK737778. A distance scale in kilobases is given. The transposase genes (tnpA, tnpB, and tnpC), antimicrobial and disinfectant resistance genes, and genes that code for other functions are shown in blue, red, and black, respectively. The 6-bp nucleotide sequences at the transposon junctions are shown in boxes. The disrupted radC genes are indicated by asterisks. The positions of primers circ-fw/circ-rev used to detect the presence of the circular intermediates are shown by black arrows.