The European Committee on Antimicrobial Susceptibility Testing (EUCAST) changed the definition of the ‘intermediate’ (I) category in 2019, now defined as ‘susceptible, increased exposure’. We previously reported an increase in prescriptions for antibiotics still reported as ‘S’, compared with those now reported as ‘I’. This study aimed to evaluate the influence of a more explicit abbreviation (SFP or ‘Susceptible increased exposure’) than ‘I’ on the use of overly broad-spectrum antibiotics for the treatment of infections caused by wild-type (WT) Pseudomonas aeruginosa .

A retrospective observational multicenter study was conducted across five hospitals. Two study periods were defined, before and after the implementation of the new abbreviation (from September 2020 to February 2022, and from March 2022 to August 2023). All patients with an infection caused by WT P. aeruginosa treated with β-lactams were included. The main endpoint was the proportion of patients treated with an overly broad-spectrum antibiotic treatment by meropenem or ceftolozane/tazobactam.

A total of 279 patients were included. No difference between groups was found, in terms of infection, microbiology, or demographic characteristics. Eight overly broad-spectrum antibiotic treatments by meropenem or ceftolozane/tazobactam were observed in Period 1 (5.6 %), versus one in Period 2 (0.7 %; p  = 0.026). No overly broad-spectrum treatment was observed when the antimicrobial stewardship team had given advice.

The French recommendations derived from the EUCAST guidelines, with a new abbreviation, have contributed to a reduction in the prescription of broad-spectrum antibiotics and have helped mitigate clinicians’ misunderstanding of the previous guidelines.