Evolutionary adaptation of KPC-2-producing Pseudomonas aeruginosa high-risk sequence type 463 in a lung transplant patient

Objectives

KPC-2-producing Pseudomonas aeruginosa high-risk sequence type (ST) 463 is increasingly prevalent in China and poses severe threats to public health. In this study, we aimed to investigate within-host adaptive evolution of this clone during therapy.

Methods

Using nine serial respiratory isolates from a post-lung transplantation patient undergoing multiple antibiotic treatments, we conducted genomic, transcriptomic and phenotypic analyses to uncover the adaptive mechanisms of a KPC-2-producing ST463 P. aeruginosa strain.

Results

The early-course isolates exhibited low-level resistance to ceftazidime/avibactam (CZA), facilitated by the bla_KPC-2 gene's presence on both chromosome and plasmid, and its overexpression. Comparative genomic analysis revealed that chromosomal integration of bla_KPC-2 resulted from intracellular replicative transposition of the plasmid-derived IS26-bla_KPC-2-IS26 composite transposon. As the infection progressed, selective pressures, predominantly from antibiotic interventions and host immune response, led to significant genomic and phenotypic changes. The late-course isolates developed a Δ242-GT-243 deletion in plasmid-encoded bla_KPC-2 (bla_KPC-14) after sustained CZA exposure, conferring high-level CZA resistance. Increased expression of pili and extracellular polysaccharides boosted biofilm formation. A D143N mutation in the global regulator vfr rendered the strain aflagellate by abrogating the ability of fleQ to positively regulate flagellar gene expression. The enhancement of antibiotic resistance and immune evasion collaboratively facilitated the prolonged survival of ST463 P. aeruginosa within the host.

Conclusions

Our findings highlight the remarkable capacity of ST463 P. aeruginosa in adapting to the dynamic host pressures, supporting its persistence and dissemination in healthcare.