Connor Rossel (Zuyderland Medisch Centrum)

Summary of presentation:
In the intensive care unit (ICU), nosocomial acquisition of multidrug resistant Enterobacteriaceae (MDRE) may lead to adverse patient outcomes; yet, investigating the link between patient colonization and environment reservoirs is often not straightforward in a non-outbreak setting. This study aimed to characterize the patient-environment transmission dynamics of MDRE strains with a common resistance phenotype and genotype at the ICU wards of two hospitals.

Sink drains, faucet aerators, high-touch sites of medical devices and beds of (non-)patient rooms were repetitively sampled over the course of 18 months (2022 to 2023). Patient isolates and epidemiological data were collected retrospectively (2017 to 2022) and prospectively (during environment sampling). Inclusion criteria for MDRE isolates were resistance to 3rd-generation cephalosporins, gentamicin, ciprofloxacin and cotrimoxazole; and PCR positive for antimicrobial resistance genes blaCTX-M-15, qnrB1 and blaOXA-1—aac(6’)-Ib-cr. Patient and subsetted environment isolates were whole genome sequenced using Illumina technology. Clonal clusters were identified with SNP-analysis (≤25 SNPs), and further assessed through spatiotemporal epidemiological links.

Overall, 553 environment isolates (primarily sink drains; 97,1%) and 136 isolates from 91 patients were collected. Most environment isolates (98,7%) and patient isolates (91,2%; 80 patients) were derived from one ICU. Clonal assessment revealed a total of 19 patient-environment SNP-clusters, which incorporated 75 environment and 36 patient isolates from eight Enterobacteriaceae spp. Epidemiological investigation showed spatial links with environment isolates for 31 patients. Furthermore, temporal links indicated possible transmission events from sink-to-patient for seven patients, and from patient-to-environment for three patients.

ICU sinks form an inherent and persistent risk-factor in the exchange of MDRE with patients. This risk appeared highly diffuse through various species and clones in this non-outbreak setting. The patient colonization rates can likely be reduced through reconsideration of sink requirement in the ICU environment, combined with prospective genomic monitoring of sink drains and patient MDRE isolates to facilitate targeted interventions.