FIG 6 .
Proposed mechanisms of CREC evolution and dissemination. (A) Plasmid uptake followed by clonal dissemination. ST171 was highly associated with an IncFIA plasmid found to harbor blaKPC-3 in a representative isolate, suggesting that plasmid uptake followed by clonal dissemination was the dominant mechanism of carbapenem resistance in this predominant clonal lineage. (B) Uptake of blaKPC-harboring plasmids into a predominantly ESBL clone. ST78 demonstrated multiple independent plasmid uptake events. (C) Uptake of diverse plasmids into sporadic clones. Independent events of plasmid uptake into multiple different clones involved multiple different carbapenemase genes, including blaKPC-2. (D) Dissemination of a hypertransmissible plasmid. We detected IncN plasmids harboring blaKPC-3 in several different clonal sublineages, suggesting that this may be a highly transmissible plasmid. (E) Carbapenem resistance in non-carbapenemase-producing isolates. A subset of CREC isolates did not harbor blaKPC or other known carbapenemases.