Comparison of Tn5397 from Clostridium difficile, Tn916 from Enterococcus faecalis and the CW459tet(M) element from Clostridium perfringens shows thatthey have similar conjugation regions but different insertion and excisionmodules

Comparative analysis of the conjugative transposons Tn5397 from Clostridium difficile and Tn916 from Enterococcus faecalis, and the CW459tet(M) elemen t from Clostridium perfringens, has revealed that these tetracycline-resist ance elements are closely related. All three elements contain the tet(M) re sistance gene and have sequence similarity throughout their central region. However, they have very different integration/excision modules. Instead of the int and xis genes that are found in Tn916, Tn5397 has a large resolvas e gene, tndX, The C. perfringens element encodes the putative Int459 protei n, which is a member of the integrase family of site-specific recombinases but is not closely related to Int from Tn916, Based on these studies it is concluded that the clostridial elements have a modular genetic organization and were derived independently from distinct mobile genetic elements.