Effectiveness of traditional non-carbapenem β-lactams vs. novel β-lactams for the treatment of carbapenem-resistant Pseudomonas aeruginosa: a retrospective cohort study.

Background: The World Health Organization (WHO) has identified carbapenem-resistant Pseudomonas aeruginosa (CRPA) as one of the three critical priority pathogens. There is scarce literature evaluating the treatment outcomes in patients with CRPA infections treated with traditional non-carbapenem β-lactam (NCBL) agents. Thus, this study aims to assess the effectiveness of traditional NCBL compared to novel β-lactam agents (NVL) for treating non-carbapenem β-lactam -susceptible CRPA.

Methods: A single-center retrospective cohort study was conducted between January 2016 and December 2022. The study included adult patients 18 years and older with infection due to CRPA who were treated based on microbiology sensitivity with traditional NCBL or NVL for more than 48 h. The primary outcome was 30-day mortality.

Results: 124 patients were included: 98 (79%) in the NCBL group and 26 (20.9%) in the NVL group. 78 (62.9%) patients were male. The median (interquartile range (IQR)) age of included patients was 64 (45, 77) years. A total of 84 (67.7%) patients were critically ill, with an overall median (IQR) APACHE II score of 18 (13.5, 23). The rates of 30-day mortality in NCBL and NVL groups were 41 (41.8%) and 12 (46.2%), respectively; P = 0.692.

Conclusion: In patients with CRPA infections susceptible to traditional NCBL, there was no statisticallly significant difference in 30-day mortality among patients who were treated with traditional NCBL compared with NVL. Further studies with larger sample sizes are needed to confirm these findings.