New Delhi Metallo-β-Lactamase from Traveler Returning to Canada

An Escherichia coli isolate with New Delhi metallo-β-lactamase was isolated from a patient with pyelonephritis and prostatitis who returned to Canada after recent hospitalization in India. The patient was successfully treated with ertapenem and fosfomycin. This patient highlights the role of international travel in the spread of antimicrobial drug resistance and blaNDM-1.

NDM-1 in Traveler, Canada was further identifi ed by digestion with BstF5I (New England Biolabs, Ipswich, MA, USA).
Multilocus sequencing typing (MLST) was performed on MH01 by using 7 conserved housekeeping genes (adk, fumC, gyrB, icd, mdh, purA, and recA). The MLST protocol, including allelic type and sequence type assignment methods, is detailed at http://mlst.ucc.ie/mlst/dbs/Ecoli. MH01 was assigned to 1 of the 4 main E. coli phylogenetic groups (A, B1, B2, D) by using a multiplex PCRbased method (10). Plasmid sizes were determined by using protocols and conditions described (11) and assigned to plasmid families by PCR-based replicon typing (12). Conjugation experiment was performed by mating-out assays with a selection agar containing different β-lactams (IMP 2 μg/mL, ceftazidime 4 μg/mL respectively) and by using E. coli C600N as recipient.
E. coli MH01 was positive for MBL production by MBL Etest. Isoelectric focusing showed that E. coli MH01 produces 2 β-lactamases with isoelectric points of 5.2 and 8.9; PCR with sequencing identifi ed these enzymes as NDM-1 and CTX-M-15, respectively. The isolate was positive for aac(6′)-Ib (but not aac(6′)-Ib-cr) and belonged to MLST clone 101 and phylogenetic group B1. E. coli MH01 harbored 4 plasmids of 75 kb, 165 kb, 300 kb, and 400 kb. E. coli (MH01A) transconjugant with an MBL phenotype was obtained, and plasmid analysis showed that it harbored a 75-kb plasmid. PCR confi rmed that the transconjugant contained bla NDM that was untypeable by PCR-based replicon typing. The bla CTX-M-15 was identifi ed on the 165-kb plasmid that belonged to incompatibility groups IncA/C and IncFII. These results were similar to those obtained by Poirel et al. (13).

Conclusions
Kumarasamy et al. (5) recently provided evidence that NDM-producing Enterobacteriaceae (mostly K. pneumoniae and E. coli) are widespread in the Indian subcontinent. They also found that many patients in the United Kingdom infected with bacteria that produce NDM-1 had been hospitalized on the Indian subcontinent. The patients sought care for a variety of hospital-and community-associated infections; UTIs were the most common clinical infections. NDM-producing Enterobacteriaceae also have recently been isolated from patients residing in the United States (14), Netherlands (15), and Australia (5); all patients had received medical care while visiting India.
Our fi ndings add Canada to the growing list of countries from which these bacteria have been isolated. An E. coli isolate with NDM-1 and belonging to the same sequence type has been reported from Australia from a patient previously hospitalized in Bangladesh (13). Isolation of the same clone in 2 patients in different countries without any obvious contact underscores the probable acquisition of these bacteria during receipt of medical care in the subcontinent and suggests that E. coli ST101 with NDM-1 may be widespread throughout the region. The recent pandemic caused by E. coli clone ST131, which produces CTX-M types of β-lactamases, highlights the ability of certain clones to spread rapidly. E. coli ST101 with NDM-1 may have the potential to cause a similar pandemic.
The worldwide spread of Enterobacteriaceae-producing NDMs has serious implications for the empiric treatment of hospital-and community-associated infections because of the multiresistant nature of these bacteria, which severely limits treatment options. Worse, few antimicrobial drugs being developed have activity against gram-negative bacteria. If the emerging public health threat of international travel in the spread of antimicrobial resistance is ignored, the medical community may face carbapenem-resistant Enterobacteriaceae that cause common infections such as UTIs.