Dissemination of -Positive ST308 Clone in Singapore

Pseudomonas aeruginosa ST308 clone has been reported to carry carbapenemase genes such as and but has been rarely associated with . A total of 199 P. aeruginosa ST308 clinical and environmental isolates obtained between April 2019 and November 2020 from a tertiary-care hospital in Singapore were characterized using whole-genome sequencing. In addition, 71 -positive ST308 whole-genome sequences from two other local tertiary-care hospitals in Singapore and 83 global -negative ST308 whole-genome sequences in public databases were included to assess phylogenetic relationships and perform genome analyses. Phylogenetic analysis and divergent time estimation revealed that -positive P. aeruginosa ST308 was introduced into Singapore in 2005 (95 % highest posterior density: 2001 to 2008). Core genome, resistome, and analyses of all local -positive ST308 isolates showed chromosomal integration of multiple antibiotic resistance genes (ARGs) [, , , , , (), , , and ], which was absent in global -negative ST308 sequences. Most ARGs and virulence genes were conserved across isolates originating from the three different local hospitals. Close genetic relatedness of the -positive ST308 clinical and environmental isolates suggests cocirculation between the hospital environment and human hosts with the hospital environment as a potential reservoir. Core genome single nucleotide polymorphism analyses revealed possible clonal transmission of -positive ST308 isolates between the three hospitals over 7 years. Bloodstream isolates accounted for six of 95 (6.3%) clinical isolates. This study reports the introduction of a pathogenic -positive P. aeruginosa ST308 more than a decade ago in Singapore and warrants surveillance for wider dissemination. P. aeruginosa is a Gram-negative opportunistic pathogen ubiquitously found in the environment and a major cause of nosocomial infections. While the P. aeruginosa ST308 clone has been known to bear and among global isolates, reports of -positive P. aeruginosa ST308 are rare. The local -positive P. aeruginosa ST308 isolates detected in this study appear to be unique to this region, with evidence of chromosomal acquisition of multiple ARGs compared to global -negative P. aeruginosa ST308 isolates. Surveillance in Singapore and beyond for dissemination is essential to determine whether existing measures are sufficient to control the spread of this ST308 clone.