Local outbreak of extended-spectrum beta-lactamase SHV2a-producing Pseudomonas aeruginosa reveals the emergence of a new specific sub-lineage of the international ST235 high-risk clone

Background: Pseudomonas aeruginosa is a major bacterial pathogen responsible for hospital-acquired infections. Although its epidemiology is considered as non-clonal, certain international high-risk multidrug-resistant clones have been recognized. Aim: From the first report of an intra-hospital outbreak due to an SHV2a-producing P. aeruginosa strain, to describe the emergence of a new ST235-specific lineage har-bouring this rare extended-spectrum beta-lactamase (ESBL). Methods: Between May and October 2018, four patients hospitalized in the cardiovascular intensive care unit of a French teaching hospital were infected by a multidrug-resistant P. aeruginosa isolate. Serotype and antimicrobial susceptibility were tested; multi-locus sequence type (MLST), core genome MLST, and resistome were determined through whole genome sequencing. A phylogenetic analysis based on single nucleotide polymorphism was performed using available ST235 genomes. Findings: The four strains were susceptible to colistin, ciprofloxacin, ceftazidime -avibactam, and ceftolozane-tazobactam. bla(SHV2a )was identified in each genome of this ST235-011 serotype cluster that showed an identical cgMLST profile (0-2 out of 4162 different alleles). The phylogenic analysis of 162 ST235 genomes showed that only four other strains harboured a bla(SHV2a), originating from France and USA, clustering together although being different from the outbreak strains. Conclusions: Among the ST235 P. aeruginosa strains, a sub-lineage sharing a common genetic background and harbouring the bla(SHV2a) ESBL seems to emerge from different locations, yielding secondary local outbreaks. (C) 2019 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.