Assessing the role of environment in Pseudomonas aeruginosa healthcare-associated bloodstream infections: a one-year prospective survey

Deciphering precise sources and patterns of healthcare-associated Pseudomonas aeruginosa colonization/infection is crucial in defining strategies of prevention and control. To prospectively investigate the role of hospital environment in P. aeruginosa nosocomial bloodstream infections (Pa-BSIs) during one year in a tertiary-care hospital. Clinical records of patients presenting Pa-BSIs after >48 h of hospitalization were investigated to confirm the nosocomial character of BSIs and identify the routes of entry and risk factors. Environmental investigations were performed to track P. aeruginosa source/reservoir along the care pathway. Clinical and environmental strains were compared by whole-genome sequencing to identify the route of contamination from hospital environment to patients. Fifty-three BSIs episodes in 49 patients were considered as nosocomial, mostly involving men (73%), with an average age of 62.4 years, immunosuppressed in >40% of cases, and after previous antibiotic therapy in almost 92% of cases. BSIs occurred after 27 days of hospitalization on average. The main routes of entry were urinary (30%, on indwelling catheters for two-thirds of cases) and cutaneous (17%, catheter-related in almost 80% of cases). P. aeruginosa was found in 16 out of 49 investigations, representing 34 positive samples, including 54% of sink traps, 23% of water, and 20% of tap aerators. An epidemiological link was established between environmental and clinical strains only for eight patients, representing 15% of nosocomial BSIs. The hospital environment usually considered as the main source of P. aeruginosa healthcare-associated infections was identified as responsible for nosocomial BSIs in only 15% of patients. Since the implementation of water and hospital environment management, one may hypothesize that P. aeruginosa has become a community-acquired pathogen with a nosocomial expression in infection.