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

Abstract Objectives Pseudomonas aeruginosa is a major bacterial pathogen responsible for hospital-acquired infections. Although its epidemiology is considered as non-clonal, some particular international high-risk multidrug resistant clones have been recognized. From the first report of an intra-hospital outbreak due to a SHV2a producing P. aeruginosa strain, we described the emergence of a new ST235 specific lineage harboring this uncommon extended spectrum beta lactamase. 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; 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. Results The four strains were susceptible to colistin, ciprofloxacin, ceftazidime-avibactam and ceftolozane-tazobactam. blaSHV2a was identified in each genome of this ST235 - O11 serotype cluster that showed an identical cgMLST profile (0 to 2 out of 4162 different alleles). The phylogenic analysis of 162 ST235 genomes showed that only four other strains harbored a blaSHV2a, originating from France and USA, clustering together although being different than the outbreak strains. Conclusions Among the ST235 P. aeruginosa strains, a sub-lineage sharing a common genetic background and harbouring the blaSHV2a extended-spectrum beta-lactamase seems to emerge from different locations, yielding secondary local outbreaks.