IncN plasmid carried blaIMP-6 in concealed-type carbapenem-susceptible Escherichia coli

The carbapenem-susceptible carbapenemase-producing Enterobacteriaceae is a current issue, because it carries carbapenemase genes but undetectable by antibiotics susceptibility patterns only. In 2010, imipenem and meropenem-susceptible but blaIMP-6-positive Escherichia coli A56-1S strain was isolated from urine specimen in Japan, and the Carba NP test was negative. Meropenem-resistant E. coli A56-1R strain was selected from the susceptible A56-1S by 1 ?g/mL meropenem. Whole genome sequencing was performed using MiSeq and PacBio RSII sequencer, and comparative genome analysis of these strains revealed that the IS26 insertion into transcriptional factor gene was found in A56-1R, while the transcriptional factor gene is intact in A56-1S.