Pseudomonas aeruginosa strains isolated from environments and patients analysed by cgMLST: The dominance of the emerging high-risk clone ST463 from intensive care unit in East China

Background: Carbapenem-resistant Pseudomonas aeruginosa sequence type 463 (ST463-CRPA) with high-virulence and high-resistance has emerged and spread rapidly in East China. The aim of the study was to investigate the distribution and characteristics of the emerging high-risk ST463-CRPA in intensive care unit (ICU) in East China. Methods: : The 11-month-span study investigated the epidemiological characteristics, genetic composition, and transmission pattern of CRPA isolated from patients and environments of 5 different ICUs in a large teaching hospital in East China. Whole-genome sequencing, antibiotic susceptibility testing and biofilm-forming ability testing were performed in all CRPA isolates. The molecular epidemiological characteristics and the phylogenetic relationships of isolates from different sources were assessed using multi-locus sequence typing (MLST) and core genome multi-locus sequence typing (cgMLST). Bacterial virulence was assessed using a Galleria mellonella infection model. Results: : According to the MLST scheme, all of CRPA isolates fell into 25 defined STs, of which 24.07% (13/54) CRPA belonged to ST463 as the dominant ST in ICUs. All 13 ST463-CRPA strains, including 4 from patients and 9 from environments mainly in washbasins, carried bla KPC-2 gene with exoU+ / exoS+ virulence genotype showing difficult-to-treat resistance (DTR) phenotype. ST463-CRPA had higher biofilm-forming ability and mortality of infected larvae than non-ST463-CRPA (P<0.05). No differences on virulence were detected between the CRPA from environments and infected patients. CgMLST results revealed that several ST463-CRPA strains isolated from different ICUs had genetic relationship. Notably, 3 ST463 strains harboring both bla AFM-1 and bla KPC-2 genes with 41-59 SNPs difference were isolated from different ICUs. Conclusions: : In combination with epidemiological data linked in time and space, the cgMLST results elucidated polyclonal dissemination of CRPA and a distribution of ST463-CRPA among ICUs in a large hospital of East China. As the dominant ST found in ICU especially in environments, KPC-ST463-CRPA might be considered a strain with potential to cause a future outbreak, which could acquire the bla AFM gene additionally, leading to the resistance to last-resort antibiotics. Hence, it’s worth our vigilance about the growing prevalence of ST463-CRPA in ICU of East China. Meanwhile, it’s important to strengthen the management of ICU environment, especially the water reservoirs.