Nosocomial Transmission of New Delhi Metallo-β-Lactamase-1-ProducingKlebsiella pneumoniaein Toronto, Canada
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Design.An analysis of a cluster of New Delhi metallo-β-lactamase-l-producingKlebsiella pneumoniae(NDMl-Kp) and a retrospective case-cohort analysis of risk factors for acquisition in contacts of NDM1-Kp-positive patients.Setting.A 1,100-bed Canadian academic tertiary care center.Patients.Two index patients positive for NDMl-Kp as well as 45 contacts (roommates, ward mates, or environmental contacts) were investigated.Methods.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 ofblaNDM-1was confirmed by multiplex polymerase chain reaction. Clonality was assessed with pulsed-field gel electrophoresis (PFGE) using restriction enzymeXbaI.Results.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).Conclusion.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.
