Low Prevalence of Among Clinical Enterobacteriaceae Isolates and Co-transfer of and from Separate Donors.

and co-harboring isolates have been reported, usually reside on different plasmids, suggesting co-transfer possibility of the two genes from separate donors to the same recipient strain. This study aims at screening and characterization of carrying Enterobacteriaceae in Northern China, and studying the transfer ability of alone and in company with from a second donor. Three strains and one strain carrying gene were screened out from 1992 isolates in our study. Co-existence of multiple resistance genes was found in the -carrying strains, but none of them carried . One demonstrated an single nucleotide polymorphism (SNP) (A-G) at -10 region of , and one showed 2 SNPs (G-T and G-A) in the Shine-Dalgarno sequence-like region of . The gene was located on plasmids of about 33-276 kb, and capable of transferring alone in three out of four -positive isolates by conjugation. Co-transfer ability analysis demonstrated that from 13-68, which could not be transferred alone to C600, was successfully transferred in company with from ATCC BAA-2146. showed low incidence in our Enterobacteriaceae isolates. Co-transfer ability of and NDM-1 from separate donors provides direct evidence for the emergence of the and bla co-harboring isolates.