Outbreak of OXA-48-producing Enterobacterales in a haematological ward associated with an uncommon environmental reservoir, France, 2016 to 2019

The hospital water environment, including the wastewater drainage system, is increasingly reported as a potential reservoir for carbapenemase-producing Enterobacterales (CPE). We investigated a persistent outbreak of OXA-48 CPE (primarily Citrobacter freundii) in a haematological ward of a French teaching hospital by epidemiological, microbiological and environmental methods. Between January 2016 and June 2019, we detected 37 new OXA-48 CPE-colonised and/or ‑infected patients in the haematological ward. In October 2017, a unit dedicated to CPE-colonised and/or ‑infected patients was created. Eleven additional sporadic acquisitions were identified after this date without any obvious epidemiological link between patients, except in one case. Environmental investigations of the haematological ward (June–August 2018) identified seven of 74 toilets and one of 39 drains positive for OXA-48 CPE (seven C. freundii, one Enterobacter sakazakii, one Escherichia coli). Whole genome comparisons identified a clonal dissemination of OXA-48-producing C. freundii from the hospital environment to patients. In addition to strict routine infection control measures, an intensive cleaning programme was performed (descaling and bleaching) and all toilet bowls and tanks were changed. These additional measures helped to contain the outbreak. This study highlights that toilets can be a possible source of transmission of OXA-48 CPE.