New Delhi metallo-β-lactamase-producing carbapenem-resistant Escherichia coli associated with exposure to duodenoscopes

Abstract

Importance: Carbapenem-resistant Enterobacteriaceae (CRE) producing the New Delhi metallo-β-lactamase (NDM) are rare in the United States, but have the potential to add to the increasing CRE burden. Previous NDM-producing CRE clusters have been attributed to person-to-person transmission in health care facilities.

Objective: To identify a source for, and interrupt transmission of, NDM-producing CRE in a northeastern Illinois hospital.

Design, setting, and participants: Outbreak investigation among 39 case patients at a tertiary care hospital in northeastern Illinois, including a case-control study, infection control assessment, and collection of environmental and device cultures; patient and environmental isolate relatedness was evaluated with pulsed-field gel electrophoresis (PFGE). Following identification of a likely source, targeted patient notification and CRE screening cultures were performed.

Main outcomes and measures: Association between exposure and acquisition of NDM-producing CRE; results of environmental cultures and organism typing.

Results: In total, 39 case patients were identified from January 2013 through December 2013, 35 with duodenoscope exposure in 1 hospital. No lapses in duodenoscope reprocessing were identified; however, NDM-producing Escherichia coli was recovered from a reprocessed duodenoscope and shared more than 92% similarity to all case patient isolates by PFGE. Based on the case-control study, case patients had significantly higher odds of being exposed to a duodenoscope (odds ratio [OR], 78 [95% CI, 6.0-1008], P < .001). After the hospital changed its reprocessing procedure from automated high-level disinfection with ortho-phthalaldehyde to gas sterilization with ethylene oxide, no additional case patients were identified.

Conclusions and relevance: In this investigation, exposure to duodenoscopes with bacterial contamination was associated with apparent transmission of NDM-producing E coli among patients at 1 hospital. Bacterial contamination of duodenoscopes appeared to persist despite the absence of recognized reprocessing lapses. Facilities should be aware of the potential for transmission of bacteria including antimicrobial-resistant organisms via this route and should conduct regular reviews of their duodenoscope reprocessing procedures to ensure optimal manual cleaning and disinfection.

Figure 1.

Network Diagram of Case Patients NDM indicates New Delhi metallo-β-lactamase. This diagram illustrates the suspected modes of transmission of NDM-producing Escherichia coli among case patients. Each box represents a case patient. Dashed lines connect case patients with a suspected source of NDM-producing E coli (eg, overlapped in the same hospital with a patient with NDM-producing E coli, but did not share a room or ward with that patient). Patient identifiers beginning with a C were identified through clinical culture and are numbered in order of date of positive culture; those beginning with an S were identified through screening culture and are ordered by date of endoscopic retrograde cholangiopancreatography procedure (if applicable). Thirteen case patients had exposure to more than 1 duodenoscope prior to their NDM-positive sample collection date (2 had exposure to >1 duodenoscope associated with the outbreak [C5 and S21]; 11 had exposure to 1 outbreak-associated duodenoscope and to duodenoscopes not associated with the outbreak). Case patients with >1 duodenoscope exposure are included with the patient notification group in which they were first identified.

Figure 2.

Pulsed-Field Gel Electrophoresis (PFGE) Dendrogram of Case Patients This figure provides the results of PFGE analysis for NDM-producing Escherichia coli isolates recovered from 39 case patients and duodenoscope A. All isolates have greater than 92% similarity by PFGE and are considered highly related.