Pseudomonas aeruginosa epidemic high-risk clones and their association with horizontally-acquired β-lactamases: 2020 update.

Abstract Pseudomonas aeruginosa global clones associated with multidrug resistant (MDR) or extensively drug resistant (XDR) phenotypes, denominated high-risk clones, are a growing threat in hospitals world-wide. Here we provide a 2020 update of nosocomial MDR/XDR high risk clones. According to their prevalence, global spread and association with MDR/XDR profiles and concerning extended spectrum β-lactamases and carbapenemases, the world-wide top 10 P. aeruginosa high-risk clones includes ST235, ST111, ST233, ST244, ST357, ST308, ST175, ST277, ST654 and ST298. ST235 is certainly the most relevant high-risk clone, showing a world-wide dissemination associated with over 60 different β-lactamase variants, including multiple carbapenemases from classes A and B. Moreover, ST235 shows a highly virulent phenotype associated with a high mortality rate, likely due to the production of the ExoU+ cytotoxin. ST111 and ST233 are also world-wide disseminated MDR/XDR clones, particularly linked to VIM-2 metallo-β-lactamase (MBL), whereas ST244 is a very prevalent clone not always associated with MDR/XDR profiles. ST357, ST308 and ST298 are also ExoU+ and are therefore potentially associated with a higher virulence. In contrast, ST175, prevalent in some European countries, shows an MDR/XDR phenotype frequently caused by specific chromosomal mutations and is associated with a lower virulence. Finally, ST277 is highly prevalent in Brazil and is specifically associated with the MBL SPM. A deeper understanding of the underlying factors driving the success of high-risk clones, including the reported increased capacity for acquiring exogenous determinants, increased spontaneous mutation rates or higher ability to develop biofilms is required to develop global strategies to combat them.