Putative Conjugative Plasmids with <i>tcdB</i> and <i>cdtAB</i> Genes in <i>Clostridioides difficile</i>

Abstract

C lostridioides difficile spores may differentiate in the colon of susceptible humans into vegetative cells and release 1 or 2 large clostridial cytotoxins (TcdA, TcdB) or a binary toxin with ADP-ribosyltransferase activity (CDT), or both, to cause colitis and diarrhea (1). When present, genes for TcdA, TcdB, and CDT are almost without exception encoded by 2 separate chromosomal loci known as PaLoc and CdtLoc (2). Recent discovery of clade C-I strains SA10-050 and