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Mobile colistin resistance (MCR-1) transmitted via a duodenoscope

  • Multidrug-resistant Gram-negative bacteria are increasingly demonstrating resistance even to reserve antibiotics such as colistin.

  • Colistin-resistant Klebsiella pneumoniae was detected in two patients in a US acute care hospital.

  • Transmission of the colistin-resistant pathogen most likely occurred by means of a duodenoscope used in both patients.

Reserve antibiotics such as colistin are increasingly being used to treat severe infections caused by multidrug-resistant Gram-negative bacteria. However, more and more, these reserve antibiotics are demonstrating resistance. For example, the plasmid-mediated mobile colistin resistance gene (MCR-1) was first discovered in enterobacteria in China in 2015. The enzyme MCR-1 makes bacteria resistant to colistin and other antibiotics from the polymyxin group. Later, the mobile resistance gene was detected in enterobacteria worldwide, including in more than 25 patients in the United States – a development that also has consequences for endoscopy, as is demonstrated by the study by Shenoy et al [1].

MCR-1-positive Klebsiella pneumoniae in the duodenoscope

Shenoy et al. described, for the first time, the transmission of MCR-1-bearing Klebsiella pneumoniae via a duodenoscope [1]. In the case description, a closely related MCR-1-positive Klebsiella pneumoniae was isolated from clinical cultures in two patients in a US acute care hospital. The only epidemiological link identified was a duodenoscope used in both patients. However, neither the reprocessing nor the microbiological examination of the instrument channel and the distal end of the device revealed any deficiencies.

The duodenoscope was then subjected to further comprehensive analyses. During the course of the review, Klebsiella pneumoniae and Escherichia coli were, in fact, recovered from the duodenoscope. These bacteria were different from the clinical isolates and did not carry a colistin-resistant gene. Further analyses and evaluations finally provided clarity: Adhesive had come loose at the distal end and, after disassembly, foreign material was found inside the distal cap. This area of the device was inaccessible for reprocessing, which led to the accumulation of biomaterial and eventual transmission of MCR-1-bearing Klebsiella pneumoniae.

Optimizing device safety and improving laboratory capacity

The authors conclude that improving the design of the device, especially with regard to effective reprocessing, is important to prevent the transmission of multidrug-resistant pathogens [1]. According to the experts, reliable detection of colistin resistance is also currently a challenge for clinical laboratories in the USA [1]. Therefore, improved laboratory capacity for colistin susceptibility testing is urgently needed.


  1. Shenoy ES et al. Transmission of Mobile Colistin Resistance (mcr-1) by Duodenoscope, Clin Infect Dis. 2019 Apr 8;68(8):1327–1334.