Import of global high-risk clones is the primary driver of carbapenemase-producing Pseudomonas aeruginosa in Norway

Abstract

Introduction. Infections by carbapenemase-producing Pseudomonas aeruginosa (CP-Pa) are concerning due to limited treatment options. The emergence of multidrug-resistant (MDR) high-risk clones is an essential driver in the global rise of CP-Pa.Hypothesis/Gap Statement. Insights into the molecular epidemiology of CP-Pa are crucial to understanding its clinical and public health impact. Despite the low incidence of infections in Norway, global spread requires an understanding of regional dissemination patterns.Aim. This study aimed to investigate the phenotypic and genotypic characteristics of CP-Pa isolates in Norway and molecular epidemiology by utilizing available metadata.Methodology. The study collection comprised all verified CP-Pa isolated in Norway from 2006 to 2022 (n=67) obtained from clinical (75%; n=50) or screening samples (22%; n=15) or had no available information (3%; n=2). Phenotypic analyses included antimicrobial susceptibility testing against clinically relevant antipseudomonal antibiotics and comparative testing for carbapenemase production using three different methods (β-CARBA, IMI/IMD gradient test and Coris O.K.N.V.I RESIST-5). Whole-genome sequencing was performed to identify virulence factors, resistance determinants and genomic relatedness.Results. The isolates were categorized as MDR (n=39) encoding Verona integron-encoded metallo-β-lactamase (VIM) (n=28), New Delhi metallo-β-lactamase (NDM) (n=6), imipenemase metallo-β-lactamase (IMP) (n=4) or Guiana extended spectrum metallo-β-lactamase (n=1) carbapenemases or extensively drug-resistant (XDR; n=28) encoding VIM (n=11), NDM (n=9) or IMP (n=8) carbapenemases. CP-Pa numbers ranged from 1 to 7 annually, peaking at 17 in 2022. Most isolates (n=64) were associated with international travel or hospitalization abroad. Phylogenetic analyses identified nine clusters of closely related genomes, with one suspected case of domestic patient-to-patient transmission. Among 21 detected sequence types, several were global high-risk clones, including ST235 (n=12), ST111 (n=9), ST773 (n=9), ST253 (n=3), ST357 (n=3), ST395 (n=3), ST823 (n=3), ST233 (n=2), ST654 (n=2), ST260 (n=1) and ST308 (n=1), covering 72% of the Norwegian isolates. ST1047 (IMP-1) and ST773 (NDM-1) were associated with Ukrainian war victims. Carbapenemase detection rates for phenotypic tests were 88% (β-CARBA), 91% (IMI/IMD) and 94% (Coris) in our collection.Conclusion. The study highlights the low incidence yet high genomic diversity of CP-Pa in Norway and the dominance of high-risk clones linked to imports, contributing to the high proportion of XDR.

Keywords: Pseudomonas aeruginosa; carbapenemase-producing; global high-risk clones; molecular epidemiology.

Fig. 1.. Distribution of CP-Pa isolates or cases in Norway from 2006 to 2022 according to (a) sample type by year of isolation, (b) patients’ age categories, (c) clonal lineages (ST) by import countries, (d) carbapenemase variants by year of isolation and (e) O-antigen serotypes.

Fig. 2.. Phylogeny of the Norwegian collection of CP-Pa (PAN-01–PAN-67) with associated phenotypic and genotypic metadata. The rooted parsnp tree was constructed with a randomly selected reference genome (PAN-53), with a tree scale as indicated. The coupled metadata include MLST, O-antigen serotype, type 3 secretion system (T3SS) exotoxin (ExoU+ or ExoS+), carbapenemase (VIM, IMP, NDM and GES) variants and antimicrobial resistance (AMR) status (MDR or XDR) according to the shown colour codes. Additionally, the results from susceptibility testing against the indicated antipseudomonal antibiotics (squares coloured in blue, resistant; white, sensitive; or grey, area of technical uncertainty), the presence of acquired genes associated with resistance (red circle) to aminoglycosides (rmtB4 and aph(3′)-, aph(3″)-, aph(6)-, ant(2″) and ant(4′)-variants) and ciprofloxacin (qnrVC1) and the presence of mutations (green circle) in quinolone-resistance determining regions (gyrA/B and parC/E) and mutations associated with resistance to colistin (pmrB_V15I) reported by AMRFinderPlus (https://www.ncbi.nlm.nih.gov/pathogens/antimicrobial-resistance/AMRFinder/) are illustrated. MEM, meropenem; IMP, imipenem; MEM/VAR, meropenem-vaborbactam; IMP/REL, imipenem-relebactam; ATM, aztreonam; CAZ, ceftazidime; FEP, cefepime; CTV, ceftazidime-avibactam; CTAZ, ceftolozane-tazobactam; TZP, piperacillin-tazobactam; FDC, cefiderocol; AMK, amikacin; TOB, tobramycin; CIP, ciprofloxacin; COL, colistin.

Fig. 3.. Genetic relatedness between the CP-Pa (PAN-01–PAN-67) isolated at various locations in Norway. (a) MST with distance based on 3867 cg alleles and cluster (grey shading) threshold ≤12 allelic differences and (b–e) focusing on specific clusters (≥3 genomes, node distances indicated) within the tree. Each node represents one genome with colouring according to the isolation site, with codes reflecting individual hospital laboratories in the four health regions (C, central; N, north; SE, south east; and W, west).