Genome-based typing reveals rare events of patient contamination with Pseudomonas aeruginosa from other patients and sink traps in a medical intensive care unit

Abstract

Abstract Background We used genome-based typing data with the aim of identifying the routes of acquisition of Pseudomonas aeruginosa (PA) by patients hospitalized in a medical intensive care unit (MICU) over a long period in a non-epidemic context. Methods This monocentric prospective study took place over 10 months in 2019 in a 15-bed MICU that applies standard precautions of hygiene. Lockable sink traps installed at all water points of use were bleach disinfected twice a week. We sampled all sink traps weekly to collect 404 PA environmental isolates and collected all PA isolates (n = 115) colonizing or infecting patients (n = 65). All isolates had their phenotypic resistance profile determined and their genome sequenced, from which we identified resistance determinants and assessed the population structure of the collection at the nucleotide level to identify events of PA transmission. Results All sink traps were positive for PA, each sink trap being colonized for several months by one or more clones. The combination of genomic and spatiotemporal data identified one potential event of PA transmission from a sink trap to a patient (1/65, 1.5%) and six events of patient cross-transmission, leading to the contamination of five patients (5/65, 7.7%). All transmitted isolates were fully susceptible to β-lactams and aminoglycosides. Conclusions Genome-based typing revealed the contamination of patients by PA originating from sink traps to be infrequent (1.5%) in a MICU with sink trap-bleaching measures, and that only 7.7% of the patients acquired PA originating from another patient.