Transfer of macrolide-lincosamide-streptogramin B (MLS) resistance in Clostridium difficile is linked to a gene homologous with toxin A and is mediated by a conjugative transposon, Tn5398.

An MLS resistance gene designated ermBZ, from a toxigenic Clostridium difficile strain (630) could be transferred between C. difficile strains, and to and from Bacillus subtilis. The intergeneric transfer occurred in the absence of any detectable plasmid DNA and the element responsible for gene transfer entered the recipient's chromosome, behaviour which is characteristic of a conjugative transposon. The element was designated Tn5398 and was found in six C. difficile strains. Tn5398 could be transferred to the non-toxigenic strain C. difficile CD37 which lacks the genes for toxins A and B. Transconjugants from both C. difficile and B. subtilis that had received the ermBZ gene also acquired a sequence of DNA that was homologous to the part of the toxin A gene that coded for the C-terminal repeat region.