P266 Genomic and phenotypic comparisons of Pseudomonas aeruginosa ST27 strains isolated from respiratory tract and domestic environment of a cystic fibrosis patient

Pseudomonas aeruginosa is the major environmental opportunistic pathogen in cystic fibrosis (CF), able to chronically colonize patient’s airways. However, P. aeruginosa acquisition sources are poorly known. A patient attending the Montpellier CF center was sporadically colonized in 2010 by a strain of P. aeruginosa of sequence type (ST) 27 and strains of identical genotype were isolated from all water points in his home during environmental investigations in 2015 and 2020. Our objectives were: i) to compare characteristics of clinical and environmental strains to identify properties that could favor transmission to patient, ii) to study the environmental strains’ evolution between 2015 and 2020 to search for features involved in environmental persistence. Genomic (whole genome MLST analysis, Single Nucleotide Polymorphism (SNP) searches and genomic content comparison) and phenotypic (motility, biofilm formation and antibiotic susceptibility) comparisons of clinical and environmental strains were performed. Strains were closely related since their genomes differed by 4 SNP maximum. The clinical strain presented all the characteristics of first colonization strain: planktonic lifestyle and low biofilm production, wildtype antibiotic susceptibility. This strain had significantly higher swimming and twitching motilities than environmental strains. At the genomic level, a prophage (45 kpb) absent from the genome of the clinical strain was present in all the environmental strains’ genomes and its integration in the genome could have contributed to the environmental persistence. During this persistence, decreased motility and increased biofilm formation were the predominant adaptive traits. This study highlights a potential P. aeruginosa transmission from the domestic environment to the patient but also reports for the first time a persistence of P. aeruginosa for at least 5 years in a home water network.