Transmission analysis of carbapenemase-negative multidrug-resistant Pseudomonas aeruginosa in critical care settings based on whole genome sequencing and epidemiological data

Introduction Carbapenemase-producing Pseudomonas aeruginosa lead to a higher mortality rate and have a higher risk of transmission. Less is known about the transmission risk of non-carbapenemase producing multidrug-resistant P. aeruginosa. Therefore, in this study the potential transmission risk of non-carbapenemase producing multidrug-resistant P. aeruginosa were analysed by whole genome sequencing.
Methods Between 07/2017 and 03/2023 screening and clinical P. aeruginosa isolates characterized as 3MRGN were included from inpatients in non-paediatric oncological wards and intensive care units at a tertiary care hospital. Additionally, all isolates characterised as 4MRGN were included. Identification and antimicrobial susceptibility testing (AST) was done with MALDI-TOF and Vitek2, respectively. Isolates carrying a carabapenemase, as confirmed from sequenced genomes by the ResFinder pipeline (Center for Genomic Epidemiology, Copenhagen, Denmark), were excluded from the cohort. Core genome Multi Locus Sequence Typing (cgMLST) was performed for all isolates that met the inclusion criteria. Clusters were identified with SeqSphere+ software (Ridom, Germany). Non-carbapenemase producing multidrug-resistant P. aeruginosa isolates with ≤55 different alleles in cgMLST target genes were considered as possibly related. Potential transmissions were analysed on prior colonisation and aligned to epidemiological data.
Results A total of 135 non-carbapenemase producing multidrug-resistant P. aeruginosa were collected out of which 35 isolates (25.9%) of 32 patients were highly related. 19 patients (61.2%) were colonised and/or infected beforehand with a pan-susceptible P. aeruginosa. Seven genetically related clusters were identified. Despite highly related sequencing data there was rarely an epidemiological link. Solely one patient-to-patient transmission event of 3MRGN isolates could not be excluded by epidemiological data.
Summary Molecular analysis could hardly be linked to epidemiological data in the transmission of non-carbapenemase producing multidrug-resistant P. aeruginosa in critical care settings. Further data is required to critically evaluate isolation measures.