bla_GES-producing ST654 comprises a quarter of all carbapenem-resistant Pseudomonas aeruginosa in blood isolates from 15 hospitals

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) are of major clinical concern. We analyzed 85 P. aeruginosa blood isolates non-susceptible to carbapenems collected during 2021-2023 from 15 medical centers in Israel. We aimed to determine the prevalence of high-risk clones, examine clonality, test antibiotic susceptibility, and assess the presence of acquired resistance genes, including carbapenemases. Whole-genome sequencing was performed using Illumina sequencing technology. Susceptibly was determined using the broth microdilution method. In the entire sample, 43.5% were high-risk clones. A main clade (27.1% of isolates) found in multiple hospitals comprised 19 isolates belonging to the high-risk ST654 clone and four closely related isolates. The isolates in this main clade harbored a broad set of resistance genes, including GES-type genes, and 91% had a mutated outer membrane protein (OprD). Isolates in the main clade were uniformly tobramycin (TOB) resistant and 83% were ceftolozane/tazobactam resistant. In the entire sample, we found high resistance to most antipseudomonal agents, including new beta-lactam/beta-lactamase inhibitor combinations. No uniform susceptibility to an antipseudomonal agent was found. Carbapenemases were carried by 9.4% of isolates (5.9% bla_GES-5 and 3.5% bla_NDM-1) and oprD was mutated in 67% of isolates. Thus, the epidemiology of CRPA is explained by a combination of clonal expansion of a dominant high-risk clade and sporadic occurrence of mutated strains. Our findings highlight the importance of susceptibility testing using a wide panel of antibiotics when CRPA is detected. Prevention measures tracking and controlling emerging high-risk clades and clones are crucial to limit the spread of CRPA.