First nationwide survey on <i>Pseudomonas aeruginosa</i> in Bolivia: susceptibility profiles, resistome, and genomic epidemiology

Information on the molecular epidemiology of <i>Pseudomonas aeruginosa</i> 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 <i>P. aeruginosa</i> 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.