Characterization of a porcine Proteus cibarius strain co-harbouring tet(X6) and cfr

Sir, Plasmid-mediated tigecycline-resistance genes tet(X3) and tet(X4) have been reported in Enterobacteriaceae isolated from food-producing animals.1,2 Recently, chromosomally mediated tet(X4) has been found in Escherichia coli 2ZN37-2 isolated from little egrets,3 which implied the great mobility of tet(X) variant genes. Besides, since the report of the multiresistance gene cfr in Proteus vulgaris,4 subsequent studies have shown that cfr can spread through plasmids and transposons in Gram-negative bacteria.5,6 Although the tet(X) variant genes and cfr were highly mobile, no convergence of the two genes in the same strain was reported....