# Adaptive evolution of Pseudomonas aeruginosa ST299 population colonizing a hospital copper water network over a 2.5-year period

## TL;DR

This study tracks how Pseudomonas aeruginosa ST299 adapts to a hospital copper water system over 2.5 years, showing stable genomic traits that help it survive.

## Contribution

The study reveals the genomic stability and copper resistance mechanisms of Pseudomonas aeruginosa ST299 in a hospital water network.

## Key findings

- ST299-PA showed minimal genomic variation and stable resistome, virulome, and pangenome in the copper water network.
- ST299-PA had a copper resistance operon and other resistance elements absent in ST2685-PA.
- CF-colonizing ST299-PA evolved faster with patho-adaptive mutations, unlike the stable ICU-water population.

## Abstract

Background. Descriptions of genomic characters and dynamics related to Pseudomonas aeruginosa (PA) adaptation and survival in hospital water networks remain scarce but necessary for sustainable water management in hospitals.

Methods. A new copper water network in an intensive care unit (ICU) was chronically colonized by a genotype sequence type (ST) 299 of PA and sporadically by a genotype ST2685. Sixty-eight ST299-PA and four ST2685-PA strains from ICU-water samples collected over 29 months and 4 months, respectively, were studied for genomic adaptation to copper water network. PFGE and whole-genome sequencing allowing SNP, comparative genomics, resistome, virulome and pangenome analyses were performed. In order to understand the adaptive phenomena linked to the colonization niche, 16 isolates of ST299-PA colonizing a cystic fibrosis (CF) patient during 16 months were included.

Results and discussion. The 68 ST299-PA ICU-water differed by <0.15 SNPs on average. No recombination regions nor patho-adaptive mutations were identified. Resistome, virulome and pangenome were stable over the time. The genomic content included a copper resistance operon, mainly metal resistance genes, a Tn4661-like transposon, the class 1 integron and broad-spectrum efflux pumps. These elements, absent in ST2685-PA ICU-water, support the survival of ST299-PA in the copper water network. The evolutionary speed of ST299-PA CF was faster with 12.9 SNPs among strains mostly affecting genes of patho-adaptation, arguing that the primo-colonization strain was probably not adapted to the niche, in contrast to the high genomic stability observed for the ST299-PA ICU-water population signifying the primary adaptation to the water network.