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Nosocomial Transmission of New Delhi Metallo-β-Lactamase-1-Producing Klebsiella pneumoniae in Toronto, Canada

  • Christopher F. Lowe (a1), Julianne V. Kus (a1), Natasha Salt (a2), Sandra Callery (a2), Lisa Louie (a2), Mohammed A. Khan (a1), Mary Vearncombe (a1) (a2) and Andrew E. Simor (a1) (a2)...

An analysis of a cluster of New Delhi metallo-β-lactamase-l-producing Klebsiella pneumoniae (NDMl-Kp) and a retrospective case-cohort analysis of risk factors for acquisition in contacts of NDM1-Kp-positive patients.


A 1,100-bed Canadian academic tertiary care center.


Two index patients positive for NDMl-Kp as well as 45 contacts (roommates, ward mates, or environmental contacts) were investigated.


Retrospective chart reviews of all patients colonized or infected with NDM1-Kp as well as contacts of these patients were performed in order to describe the epidemiology and impact of infection prevention and control measures. A case-cohort analysis was conducted investigating 45 contacts of NDM1-Kp-positive patients to determine risk factors for acquisition of NDM1-Kp. Rectal swabs were screened for NDMl-Kp using chromogenic agar. Presence of blaNDM-1 was confirmed by multiplex polymerase chain reaction. Clonality was assessed with pulsed-field gel electrophoresis (PFGE) using restriction enzyme XbaI.


Two index cases carrying NDM1-Kp with different PFGE patterns were identified. Nosocomial transmission to 7 patients (4 roommates, 2 ward mates, and 1 environmental contact) was subsequenüy identified. Risk factors for acquisition of NDM1-Kp were a history of prior receipt of certain antibiotics (fluoroquinolones [odds ratio (OR), 16.8 (95% confidence interval [CI], 1.30-58.8); P = .005], trimethoprim-sulfamethoxazole [OR, 11.3 (95% CI, 1.84-70.0); P = .01], and carbapenems [OR, 16.8 (95% CI, 1.79-157.3); P = .04]) and duration of exposure to NDM1-Kp-positive roommates (26.5 vs 6.7 days; P< .001).


Two distinct clones of NDM1-Kp were transmitted to 7 inpatient contacts over several months. Implementation of contact precautions, screening of contacts for NDM1-Kp carriage, and attention to environmental disinfection contributed to the interruption of subsequent spread of the organism. The appropriate duration and frequency of screening contacts of NDMl-Kp-positive patients require further study.

Corresponding author
Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Room Bl 21, Toronto, Ontario M4N 3M5, Canada (
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Infection Control & Hospital Epidemiology
  • ISSN: 0899-823X
  • EISSN: 1559-6834
  • URL: /core/journals/infection-control-and-hospital-epidemiology
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