Epidemiology of healthcare-associated Pseudomonas aeruginosa in intensive care units: are sink drains to blame?

Background: Pseudomonas aeruginosa (PA) is a common cause of healthcare -associated infection (PA-HAI) in the intensive care unit (ICU). Aim: To describe the epidemiology of PA-HAI in ICUs in Ontario, Canada, and to identify episodes of sink -to -patient PA transmission. Methods: This was a prospective cohort study of patients in six ICUs from 2018 to 2019, with retrieval of PA clinical isolates, and PA -screening of antimicrobial -resistant organism surveillance rectal swabs, and of sink drain, air, and faucet samples. All PA isolates underwent whole-genome sequencing. PA-HAI was defined using US National Healthcare Safety Network criteria. ICU -acquired PA was defined as PA isolated from specimens obtained >48 h after ICU admission in those with prior negative rectal swabs. Sink -topatient PA transmission was defined as ICU -acquired PA with close genomic relationship to isolate(s) previously recovered from sinks in a room/bedspace occupied 3-14 days prior to collection date of the relevant patient specimen. Findings: Over ten months, 72 PA-HAIs occurred among 60/4263 admissions. The rate of PA-HAI was 2.40 per 1000 patient -ICU -days; higher in patients who were PA -colonized on admission. PA-HAI was associated with longer stay (median: 26 vs 3 days uninfected; P < 0.001) and contributed to death in 22/60 cases (36.7%). Fifty-eight admissions with ICUacquired PA were identified, contributing 35/72 (48.6%) PA-HAIs. Four patients with five PA-HAIs (6.9%) had closely related isolates previously recovered from their room/bedspace sinks. Conclusion: Nearly half of PA causing HAI appeared to be acquired in ICUs, and 7% of PAHAIs were associated with sink -to -patient transmission. Sinks may be an under -recognized reservoir for HAIs.