Pseudomonas aeruginosa Isolation from Urine Culture in Hospitalised Patients: Incidence of Complicated Urinary Tract Infections and Asymptomatic Bacteriurias and Impact on Treatment of the EUCAST 2020 Update

<b>Background.</b> Urinary tract infections (UTIs) and asymptomatic bacteriurias (ABU) represent a large field of interest for antimicrobial stewardship programmes especially after 2020 EUCAST update in antimicrobial susceptibility testing interpretation and the possible related increase in carbapenems' prescription rate. The aim of this study was to evaluate the impact of the 2020 EUCAST update on antibiotic prescription in UTI due to <i>Pseudomonas aeruginosa</i> organism and their characteristics. <b>Methods.</b> A retrospective observational study. We enrolled all the patients with <i>P. aeruginosa</i> isolation from urine, admitted to our hospital from 2018 to 2021. We compared demographic, clinical, and microbiological characteristics and treatment between cases before 2020 EUCAST update (period A, 2018-2019) and after it (period B, 2020-2021). <b>Results.</b> A total of 643 cases was analysed, 278 in period A and 365 in period B; 65% were ABU. Carbapenems' prescription rate significantly increased in period B when considering ABU alone (21.4% vs. 41%, <i>p</i> = 0.016) and all the treated cases (treated ABU and UTI; 27.8% vs. 41.4%, <i>p</i> = 0.013); anti-Pseudomonas cephalosporins prescription significantly decreased in period B when considering ABU alone (15.7% vs. 3.6%, <i>p</i> = 0.021), UTI alone (20.7% vs. 5.9%, <i>p</i> = 0.009) and all the treated cases (18.5% vs. 5.9%, <i>p</i> = 0.001). <b>Conclusions.</b> The 2020 EUCAST update could have contributed to an increase in carbapenem prescriptions. UTI and ABU represent a large field of interest for stewardship interventions both from a diagnostic and therapeutic point of view.