Abstract
Information on the molecular epidemiology of Pseudomonas aeruginosa and antimicrobial resistance mechanisms is still limited in some South American countries. This study aims to decipher the population structure of 111 extensive drug-resistant P. aeruginosa isolates from a national study conducted in Bolivia during 2023-2024. The antibiotic susceptibility profiles were determined for 15 antipseudomonal agents. All isolates were subjected to whole-genome sequencing (WGS), and, through bioinformatics analysis, sequence types (ST), clonal relatedness, and acquired mutation-driven and transferable resistance mechanisms were elucidated. The most active antipseudomonal agents were colistin (98.2% intermediate, MIC(50/90)=1/2 mg/L) and cefiderocol (92.7% susceptible, MIC(50/90)=0.25/4 mg/L) according to the Clinical and Laboratory Standards Institute (CLSI). High resistance rates to ceftazidime/avibactam (79.3%), ceftolozane/tazobactam (82.9%), and imipenem/relebactam (71.2%) were documented. Carbapenemases were found in 60.3%, particularly including metallo-β-lactamases (MBL), such as SPM-1 (35%), VIM-2 (9%), the co-production of NDM-1 and DIM-1 (4%), or the new IMP variant IMP-111. Extended-spectrum β-lactamases (ESBLs) were detected in 12% of the isolates, including OXA-17 (7%), PER-1 (3%), and some GES variants. The most commonly detected clone was ST277 (35%) associated with SPM-1, followed by the ST309 (25%) producer of OXA-2 and various GES, and ST235 (20%) related with OXA-17 and new IMP-111. These clones harbored other acquired resistance genes, including emerging 16S rRNA methyltransferases, RmtD and RmtG. The high resistance rates for novel beta-lactams linked to an alarming spread of high-risk clones ST277 and ST235 and the very high prevalence of MBLs and ESBLs raise significant concern. This underscores the urgent need for establishing epidemiological surveillance and infection control strategies.