Background: The patient environment is increasingly considered a major source of transmission of nosocomial bacteria to patients. In May 2019, a cluster of 3 patients with multiresistant Enterobacter cloacae was discovered in the hematology-oncology department of the Maastricht University Medical Center (built in 1991). The strains had an identical antibiogram: ESBL-positive, ciprofloxacin R, cotrimoxazole R, meropenem S, and colistin S. One neutropenic patient had a positive blood culture for this strain, resistant to the empiric treatment with piperacillin-tazobactam, but the patient recovered after switching the antibiotic regimen to meropenem. All strains were determined to be identical by amplified-fragment length polymorphism and whole-genome multi-locus sequencing typing (genotype A). New cases occurred, despite the introduction of contact isolation of positive and contact patients. Therefore, weekly point-prevalence screening was introduced, in which more newly colonized patients were identified in the subsequent weeks. Attention to hand hygiene was enforced, and the hypothesis of contamination from “wet” environmental locations was tested by performing cultures of sinks and shower drains. In June and July, 47 of 241 environmental cultures (19.5%) were positive for E. cloacae with an identical antibiogram, among which some were typed as genotype A. To diminish the environmental contamination, all siphons of sinks were replaced, and disinfection of sinks and shower drains was intensified using chlorine and soda on a daily basis. Replacement of shower drains was not possible. After this intervention, the incidence of newly colonized patients declined gradually. A change in the regimen of selective gut decontamination in hematology patients was considered as an alternative intervention, but with the decrease in new patient cases, this was not implemented. A final round of environmental cultures at the end of August revealed 8 positive cultures, of which 5 were positive for genotype A. In retrospect, this finding could be explained by the fact that the cleaning team did not follow the intensified instructions for disinfection. From week 29, genotype A E. cloacae was no longer cultured in weekly patient screenings. Based on this observation, it is important that in (re)building plans for hospitals, a master plan for the prevention of nosocomial transmission from environment to patients is incorporated.

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Disclosures: None