We report 2 outbreaks of genetically unrelated carbapenem-resistant New Delhi metallo-β-lactamase–producing Escherichia coli caused by contaminated duodenoscopes. Using endoscopes with disposable end caps, adherence to the manufacturer’s reprocessing instructions, routine audits, and manufacturer evaluation are critical in preventing such outbreaks.

Antibiotic-resistant bacteria, and more specifically, carbapenem-producing Enterobacterales (CPE) strains, are increasing worldwide. Despite their growing prevalence, in most high-income countries, the detection of CPE is still considered a low-frequency event. Sporadically, patients co-colonized with distinct CPE strains and/or different carbapenemase enzymes are detected. In this paper, we present three cases that illustrate the underlying mechanisms of co-colonization, focusing on horizontal gene transfer (HGT) and patient-to-patient transmission. We also demonstrate the diversity of CPE species and discuss the potential consequences of co-colonization.