The Macrolide-Lincosamide-Streptogramin B Resistance Determinant from Clostridium difficile 630 Contains Two erm (B) Genes

Abstract

The ErmB macrolide-lincosamide-streptogramin B (MLS) resistance determinant from Clostridium difficile 630 contains two copies of an erm(B) gene, separated by a 1.34-kb direct repeat also found in an Erm(B) determinant from Clostridium perfringens. In addition, both erm(B) genes are flanked by variants of the direct repeat sequence. This genetic arrangement is novel for an ErmB MLS resistance determinant.

Generation of an erythromycin-sensitive derivative of Clostridium difficile strain 630 (630Δerm) and demonstration that the conjugative transposon Tn916ΔE enters the genome of this strain at multiple sites

“…This indicates that erm2(B) is solely responsible for erythromycin resistance. However, the putative promoter upstream of this gene is deleted in strain 630 (Farrow et al, 2000), therefore this gene must be expressed from another upstream promoter. The erm1(B) gene from the 630˜erm strain was sequenced in its entirety and found to be identical to erm2(B).…”

Genomic analysis of the erythromycin resistance element Tn5398 from Clostridium difficile The GenBank accession number for the Tn5398 element and flanking sequence is AF109075.

“…Because of these observations it was proposed that the Erm B determinant from C. difficile resides on a conjugative transposon, Tn5398 (Mullany et al, 1995). This element has not been completely sequenced or characterized, although we have shown (Farrow et al, 2000) that it carries two identical erm(B) genes that are separated by a copy of the direct repeat (DR) sequence that is found on either side of the erm(B) gene from Clostridium perfringens (Berryman & Rood, 1995). These C. perfringens DR sequences are two directly repeated segments of DNA that primarily consist of an ORF, ORF298, which shows low levels of identity at the amino acid level to Soj and ParA proteins, flanked by highly palindromic sequences, palA and palB.…”

“…This strain carried a recombinant plasmid, pJIR1790, which contained a 19n5 kb insert. Approximately 13n5 kb of pJIR1790 was sequenced on both strands using a primer walking approach, be- ginning with primers within the Erm leader peptide and erm2(B) genes (Farrow et al, 2000). Analysis of the resultant data indicated that pJIR1790 carried a potentially novel genetic element.…”

“…These C. perfringens DR sequences are two directly repeated segments of DNA that primarily consist of an ORF, ORF298, which shows low levels of identity at the amino acid level to Soj and ParA proteins, flanked by highly palindromic sequences, palA and palB. In C. difficile strain 630 the two erm(B) genes are separated by a copy of the DR sequence and are flanked downstream by a variant of this DR sequence from which ORF298 has been deleted and flanked upstream by a DR variant that contains only the sequence downstream of palB (Farrow et al, 2000).…”

“…Hybridization analysis has indicated that MLS-resistant strains of C. difficile carry erm(B) genes (Farrow et al, 2000 ;Ha$ chler et al, 1987). The Erm B determinant carried by C. difficile strain 630 has been shown to be transferred by a conjugation-like mechanism to C. difficile (Wu$ st & Hardegger, 1983), Staphylococcus aureus (Ha$ chler et al, 1987) and Bacillus subtilis (Mullany et al, 1995).…”