Résumé
P. aeruginosa, an opportunistic pathogen of plumbing systems, is a major source of healthcare-associated infections (HCAIs), with increased involvement in intensive care units (ICU), where it is responsible for 20% of HCAIs. The emergence of carbapenem-resistant phenotypes (CRPA), identified in 20 to 25% of cases depending on the clinical ward, exposes complex clinical situations. This report is particularly worrying given that the number of PA bloodstream infections (BSIs) has been rising steadily in recent years and that attributable mortality is at least 37% in cases of CRPA. In hospital, risk factors of PA infection are linked to patients, type of cares provided and the presence of PA in hospital environment close to patient. During PA outbreaks, an association between the presence of PA in water niches and PA-HCAI onset is suggested but the contribution of the environment in PA-HCAI out of outbreak circumstances is rarely reported and controversial. The aim of this work was to describe the epidemiological characteristics of nosocomial bacteremia in a tertiary care teaching hospital, and to determine the proportion linked to an environmental reservoir. To this end, a prospective study covering the year 2022 was carried out, including all patients presenting a positive blood culture for PA at least 48 hours after hospitalization. As soon as a BSI was notified, an investigation of the patient's immediate environment was carried out to identify PA reservoir. Environmental and clinical isolates were compared using molecular typing methods (rep-PCR, MLST, WGS) to establish an epidemiological link. Once an PA reservoir was identified, 50% of BSIs were probably or possibly linked to this source, underlining the key role of the environment in the occurrence of PA HCAIs. However, contrary to all expectations, for 85% of Pa BSIs defined as hospital-acquired no environmental reservoir was identified, suggesting that PA must no longer be considered as a nosocomial pathogen stricto sensu. Since the implementation of management measures of water risk in past decades, one can hypothesize that PA has become a community-acquired pathogen of nosocomial expression for which infectious character is revealed as a result of hospital selection pressures.