Impact of selective reporting of antibiotic susceptibility testing results on meropenem prescriptions for the treatment of Pseudomonas aeruginosa infections after 2020 EUCAST criteria update: an observational study in a university hospital

Abstract Background We previously reported an increase in meropenem prescriptions for Pseudomonas aeruginosa infections in our hospital after the implementation of the 10th version of the EUCAST breakpoints table for P. aeruginosa in January 2020. As a consequence, antibiotic susceptibility testing results were adapted by masking meropenem for P. aeruginosa isolates susceptible to either ceftazidime, cefepime or piperacillin-tazobactam. We aimed to assess the changes in meropenem prescriptions after the implementation of the selective reporting. Methods In this retrospective single-centre observational study, we analysed antimicrobial therapies prescribed for P. aeruginosa infections after the susceptibility testing results have been made available over three periods: “before EUCAST update”, “after EUCAST update without selective reporting” and “after EUCAST update with selective reporting”, at Lausanne University Hospital, Switzerland. We collected epidemiological, microbiological and clinical data. The primary outcome was the prescription of meropenem to treat P. aeruginosa infections after the release of susceptibility testing results. Secondary outcomes were the use of increased dosage of non-meropenem anti-pseudomonal drugs, and IDs’ consultations rates after the release of susceptibility testing results. Results Among the 457 patients included, 65 (14.2%) received meropenem: 5/148 (3.4%) before EUCAST update, 51/202 (25.3%) after EUCAST update without selective reporting, and 9/107 (8.4%) after EUCAST update with selective reporting. Supervision and counselling from IDs as well as the use of increased dosages of non-carbapenem antibiotics increased in both periods after EUCAST update, compared to the first period, respectively: 40.5% (60/148) versus 61.4% (124/202) versus 51.4% (55/107) (P