Instability of the IncFII-Type Plasmid Carrying blaNDM-5 in a Klebsiella pneumoniae Isolate

In this study, we characterized the bla(NDM-5)-bearing plasmid in a Klebsiella pneumoniae isolate that had lost the plasmid during serial passage. We determined the complete sequences of the plasmid pCC1410-2, which was extracted from a K. pneumoniae ST709 isolate collected at a Korean hospital from which two NDM-5-producing K. pneumoniae isolates were subsequently isolated. As a result, the pCC1410-2 plasmid had a backbone structure that was similar to those of two plasmids previously reported from the same hospital, but lacked some antibiotic resistance genes (bla(TEM-1), rmtB, mphR(A), mrx(A), and mph(A)). A 9-bp repeating unit encoding three amino acids (Gln-Gln-Pro) was inserted in TraD in pCC1410-2. Thus, the pCC1410-2 plasmid might be transferred from the previously identified carbapenem-resistant K. pneumoniae, but some delections and inversions might have occurred during the process. We compared the transfer frequency and stability of the plasmids. The relative frequency of conjugative transfer and stability in the host were significantly lower in pCC1410-2 than in previously reported bla(NDM-5)-bearing plasmids in Korea. A low transfer frequency and instability in the host may cause underestimation of carbapenemase-producing Enterobacteriaceae in the clinical setting and in surveillance studies.