New Delhi Metallo-β-Lactamase-1–Producing Klebsiella pneumoniae, Florida, USA

To the Editor: New Delhi metallo-β-lactamase (NDM)–producing Enterobacteriaceae have swiftly spread worldwide since an initial report in 2008 from a patient who had been transferred from India back home to Sweden (1). Epidemiologically, the global diffusion of NDM-1 producers has been associated with the Indian subcontinent and the Balkan region, which are considered the primary and secondary reservoirs of these pathogens, respectively (1). However, recent reports suggest that countries in the Middle East may constitute another potential reservoir for NDM-1 producers (1). More than 100 NDM-producing isolates have been reported in the United States, most of which were associated with recent travel from the Indian subcontinent (2,3). We report an NDM-1–producing Klebsiella pneumoniae strain that was recovered from a patient who had been transferred from Iran to a hospital in Florida, United States.

The patient was a 72-year-old woman with diabetes who had suffered a hip fracture while residing in Iran. After fixation of the bone failed, the patient underwent hip replacement, which was complicated by dislocation and an infected hematoma. She was transferred to a hospital in Florida in February 2014 for further care. The wound culture collected upon arrival grew K. pneumoniae K351. The patient underwent surgical debridement, implant removal, and placement of an antimicrobial spacer for prosthetic joint infection. She was treated with tigecycline; however, the wound did not heal, and she underwent debridement with removal of the spacer and placement of antimicrobial beads.

K. pneumoniae K351 from the patient was resistant to all β-lactams tested, including carbapenems, and highly resistant to aminoglycosides and fluoroquinolones, retaining susceptibility only to tigecycline and colistin. PCR and sequencing revealed the presence of β-lactamase genes bla_NDM-1, bla_CTX-M-15, bla_SHV-12, and bla_TEM-1 and 16S rRNA methyltransferase genes rmtC and armA. The strain sequence type (ST) was ST147, which is one of the predominant NDM-producing K. pneumoniae lineages and has been reported in many countries (3,4). Conjugation experiments using broth and filter mating methods did not yield any Escherichia coli J53 transconjugants with bla_NDM-1, despite repeated attempts. Plasmids of K351 were extracted by using the standard alkaline lysis method and used to transform E. coli TOP10-competent cells. An E. coli transformant harboring plasmid pK351 grew on Mueller-Hinton agar plates supplemented with 200 μg/mL of ampicillin. The transformant exhibited resistance to all β-lactams, including carbapenems and aminoglycosides; this resistance could be attributed to the presence of bla_NDM-1 and rmtC in plasmid pK351, which was confirmed by PCR.

pK351 was fully sequenced on a PacBio RS II sequencing instrument (Pacific Biosciences, Menlo Park, CA) and annotated (GenBank accession no. KR351290) (5). pK351 is 106,844 bp in length, has an average GC content of 55.4%, and encodes IncFIB and IncFII-like replication proteins, with IncFIB belonging to B36 according to the replicon sequencing typing scheme (6). pK351 is most closely related (98% coverage and 99% identity) to 3 bla_NDM-1-carrying plasmids pKOX_NDM1, pRJF866, and pNDM-Ec1GN574 (GenBank accession nos. NC_021501, KF732966, and KJ812998, respectively) (Technical Appendix Figure). Compared with the 3 plasmids, pK351 is missing a 4,086-bp region between insertion sequence (IS) IS1 and IS903-like mobile elements, probably due to IS1-mediated deletion. In addition, the region containing gene ccdBA between gene resD and an IS1 remnant is replaced by a region encoding 2 hypothetical proteins in pK351. The remainder of pK351 exhibits 99.95% identity to the 3 related plasmids. The immediate genetic environment of bla_NDM-1 in pK351 is identical to that in the 3 related plasmids, encompassing bla_NDM-1 itself and the downstream sequence, flanked by 256-bp direct repeats (7).

Plasmids pKOX_NDM1 and pRJF866 were found in a K. oxytoca strain from Taiwan and a K. pneumoniae ST11 strain from Shanghai, China, respectively (7,8). K. oxytoca (pKOX_NDM1) was isolated from a patient from Taiwan who underwent surgery in Jiangxi, China. K. pneumoniae ST11 (pRJF866) was isolated from a patient in a burn unit in Shanghai just after a highly related NDM-1–producing K. pneumoniae ST11 strain was isolated from another patient in the same unit who had traveled to Jiangxi Province (8). pNDM-Ec1GN574 was detected in an E. coli strain from a patient previously hospitalized in India before being admitted to a community hospital in Canada (9). Identification of highly similar bla_NDM-1–carrying plasmids in various strain lineages and species in different locales suggests extensive horizontal transfer of these plasmids among broad-range hosts. Acquisition of these plasmids by globally distributed, multidrug-resistant K. pneumoniae lineages (ST11 and ST147) is of grave concern.

The epidemiology of NDM-1–producing Enterobacteriaceae continues to evolve. The case reported here was imported to the United States upon patient transfer from Iran (10). The unusual path for this NDM-1–producing K. pneumoniae supports the hypothesis that the Middle East might be an additional reservoir for NDM producers.

Technical Appendix

Major structural features of plasmid pK351 compared with closely related plasmids.