Abstract
By favouring the emergence, persistence and ultimately the transmission of pathogens such as Pseudomonas aeruginosa (Pa), technological niches, which are increasingly common in the hospital environment, represent a major source of nosocomial infections. To date, the adaptive dynamics of bacterial populations and the persistence of Pa have been extensively studied in chronic respiratory infections in cystic fibrosis patients, which is the main model for studying Pa. There is a lack of knowledge about its lifestyle, evolution and ability to adapt in the environment, especially in anthropized technological niches such as hospital water systems. Since the incidence of healthcare-associated infections caused by Pa is partly determined by the existence of environmental reservoirs, understanding the genomic characteristics and interbacterial interactions that underpin the adaptation, survival and, consequently, ecological success of Pa in hospital water systems remains essential to improve the control of the risk of infection. To provide answers, we have attempted to clarify the epidemiological cycle of Pa in a medical intensive care unit, based on environmental studies. Secondly, a study of the genomic microevolution of a Pa-ST299 population chronically colonizing the copper water network of this department, which has been subject to numerous selective pressures, revealed extreme genomic stability, as evidenced by an evolutionary rate of 0.15 SNPs/year. Considering the patho-adaptive mutations and the rate of SNPs identified within the Pa-ST299 strains isolated from the CF patient, it is possible to affirm that genomic evolution is habitat specific and confirms that the ST299 genotype possesses the adaptive capacities classically described at the level of the Pa species. The genomic stability highlighted within ST299 collected from the water network indicates the pre-adaptation of this genotype to the specific constraints applied to the water network. Analysis of the genomic content reveals a core genome rich in virulence factors and the presence of a copper resistance genomic island, called GI-HMR, not found in non-ST299 Pa that sporadically colonized the water network. Given the co-selection phenomena, the involvement of copper resistance in resistance to amoebic predation and patho-adaptation, this island seems to support the survival of Pa in copper water systems and is a definite advantage in the event of infection. The study of bacterial interactions between Pa and Stenotrophomonas maltophilia, through competitive motility tests and co-culture growth kinetics, did not explain the success of Pa in this technological niche. Finally, hospital water systems can be considered as pathological environmental niches that combine conditions favorable to the infectious success of Pa and should make it necessary to reconsider the use of copper as an antimicrobial agent.