Clonal spread and environmental persistence of carbapenem-resistant high-risk Pseudomonas aeruginosa in critical-care units of a Chilean national referral center for burn and trauma patients (2022)

Pseudomonas aeruginosa is an opportunistic nosocomial pathogen ranked by the World Health Organization (WHO) as a high priority for research and the development of new antimicrobial therapies. To characterize carbapenem-resistant P. aeruginosa (CRPA) isolated from patients at the Hospital de Urgencia Asistencia Pública (HUAP), Chile in 2022, and to evaluate clonal diversity, resistance mechanisms, virulence factors, and clinical associations. We analyzed 126 clinical CRPA isolates using PFGE, PCR screening of resistance and virulence genes, and whole-genome sequencing of 18 representative strains. Sequence types (STs), resistomes, and virulomes were identified, and their associations with severity, length of hospital stay, cost, and patient outcomes were evaluated. Seventy-four percent of isolates originated from critical care units, predominantly from respiratory and tissue samples. PFGE revealed 25 pulsotypes, with L and Y being the predominant types. Overall, 67% of isolates were XDR and 1% PDR. Carbapenemase genes were absent in 115 isolates, while blaVIM and blaKPC were detected in 8 and 3 isolates, respectively. The exoS + / exoU + genotype was identified in 6 isolates; whole-genome sequencing revealed eight distinct STs, including previously described high-risk clones ST654, ST395, and ST274. A resistome analysis revealed diverse aminoglycoside and β -lactam resistance determinants, while a virulome analysis confirmed the presence of exoS + / exoU + in two sequenced isolates. Carbapenem resistance was significantly associated with prolonged hospitalization (median 84 vs. 39 days), greater clinical severity, and substantially higher healthcare resource utilization, reflected by increased DRG (Diagnosis-Related Group) weights, compared with carbapenem-susceptible controls. Our findings highlight the circulation of high-risk P. aeruginosa clones in Chile and underscore the importance of molecular epidemiology in guiding infection control, optimizing antimicrobial therapy, and mitigating the clinical and economic burden of CRPA.