ICE Slu van, a 94-Kilobase Mosaic Integrative Conjugative Element Conferring Interspecies Transfer of VanB-Type Glycopeptide Resistance, a Novel Bacitracin Resistance Locus, and a Toxin-Antitoxin Stabilization System

Abstract

ABSTRACT A 94-kb integrative conjugative element (ICE Slu van) transferable to Enterococcus faecium and Enterococcus faecalis from an animal isolate of Streptococcus lutetiensis consists of a mosaic of genetic fragments from different Gram-positive bacteria. A variant of ICE Slu van was confirmed in S. lutetiensis from a patient. A complete Tn 5382 /Tn 1549 with a vanB2 operon is integrated into a streptococcal ICE Sde 3396-like region harboring a putative bacteriophage exclusion system, a putative agglutinin receptor precursor, and key components of a type IV secretion system. Moreover, ICE Slu van encodes a putative MobC family mobilization protein and a relaxase and, thus, in total has all genetic components essential for conjugative transfer. A 9-kb element within Tn 5382 /Tn 1549 encodes, among others, putative proteins similar to the TnpX site-specific recombinase in Faecalibacterium and VanZ in Paenibacillus , which may contribute to the detected low-level teicoplanin resistance. Furthermore, ICE Slu van encodes a novel bacitracin resistance locus that is associated with reduced susceptibility to bacitracin when transferred to E. faecium . The expression of a streptococcal pezAT toxin-antitoxin-encoding operon of ICE Slu van in S. lutetiensis , E. faecium , and E. faecalis was confirmed by reverse transcription (RT)-PCR, indicating an active toxin-antitoxin system which may contribute to stabilizing ICE Slu van within new hosts. Junction PCR and DNA sequencing confirmed that ICE Slu van excised to form a circular intermediate in S. lutetiensis , E. faecalis , and E. faecium . Transfer between E. faecalis cells was observed in the presence of helper plasmid pIP964. Sequence analysis of the original S. lutetiensis donor and enterococcal transconjugants showed that ICE Slu van integrates in a site-specific manner into the C-terminal end of the chromosomal tRNA methyltransferase gene rumA .