Transmission of Mobile Colistin Resistance (mcr-1) by Duodenoscope

Abstract

Background: Clinicians increasingly utilize polymyxins for treatment of serious infections caused by multidrug-resistant gram-negative bacteria. Emergence of plasmid-mediated, mobile colistin resistance genes creates potential for rapid spread of polymyxin resistance. We investigated the possible transmission of Klebsiella pneumoniae carrying mcr-1 via duodenoscope and report the first documented healthcare transmission of mcr-1-harboring bacteria in the United States.

Methods: A field investigation, including screening targeted high-risk groups, evaluation of the duodenoscope, and genome sequencing of isolated organisms, was conducted. The study site included a tertiary care academic health center in Boston, Massachusetts, and extended to community locations in New England.

Results: Two patients had highly related mcr-1-positive K. pneumoniae isolated from clinical cultures; a duodenoscope was the only identified epidemiological link. Screening tests for mcr-1 in 20 healthcare contacts and 2 household contacts were negative. Klebsiella pneumoniae and Escherichia coli were recovered from the duodenoscope; neither carried mcr-1. Evaluation of the duodenoscope identified intrusion of biomaterial under the sealed distal cap; devices were recalled to repair this defect.

Conclusions: We identified transmission of mcr-1 in a United States acute care hospital that likely occurred via duodenoscope despite no identifiable breaches in reprocessing or infection control practices. Duodenoscope design flaws leading to transmission of multidrug-resistant organsisms persist despite recent initiatives to improve device safety. Reliable detection of colistin resistance is currently challenging for clinical laboratories, particularly given the absence of a US Food and Drug Administration-cleared test; improved clinical laboratory capacity for colistin susceptibility testing is needed to prevent the spread of mcr-carrying bacteria in healthcare settings.

Keywords: Klebsiella pneumoniae; duodenoscope; infection control; medical device safety; mobile colistin resistance.

Figure 1.

Exposure investigation timeline and surveillance results. Patients exposed to the duodenoscope are shown below the timeline, from duodenoscope use during case 1’s (C1) procedure on day 1 through sequestration of the scope on day 16. The following designations were used: C for case-patients; E denoting endoscopic retrograde cholangiopancreatography (ERCP) exposure; R denoting roommate exposure; B indicating bathroom exposure, and N indicating patients identified as unit contacts. An asterisk indicates those patients who either had a stent placed during the ERCP (E3 and E4/C2) or who had an indwelling stent that was left in place following the ERCP (E5). Exposed patients who were identified as cases of mcr-1 are shown in color (orange for case 1 [C1], blue for case 2 [E4/C2]). Secondary exposures to C1 and E4/C2 were identified using a definition of shared environment informed by public health recommendations. Together, these individuals constituted the cohort for the exposure investigation. Exposed patients who were tested and had an mcr-1–negative result are shaded in solid gray. Exposed patients for whom no information was available are shown in hatched gray (eg, patient died or was discharged and lost to follow-up). Of the 7 individuals identified as healthcare-associated contacts of C1, all had been discharged from the hospital to home at the time the investigation was initiated, apart from E4/C2. Of the 26 contacts of E4/C2, 9 had been discharged to home, 13 had been transferred to a long-term acute care hospital or rehabilitation hospital, and 4 had died either in the hospital or since discharge; swabs could not be obtained from 11 of these 26 contacts.

Figure 2.

Phylogenetic tree. A maximum likelihood phylogenetic tree was constructed from an alignment of single-nucleotide variants extracted from the whole genomes of Klebsiella pneumoniae isolates from the 2 case-patients, C1 and E4/C2. Abbreviation: SNV, single-nucleotide variant.