AbstractAerococcus urinae is an uncommon uropathogen that mainly affect the elderly with predisposing conditions. Aim of the present study was to investigate the clinical and microbiological characteristics of patients with urinary tract infections (UTIs) by A. urinae and determine the antimicrobial susceptibility patterns of the isolates, over the last 3 years at our institution. The medical records and microbiological data of patients from whom A. urinae was isolated from urine cultures at the university hospital of Heraklion, Crete, Greece, between 2020 and 2022, were retrospectively analyzed. The isolates were identified by the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Susceptibilities for antimicrobial agents were determined by the disk diffusion method and results were interpreted using the 2024 EUCAST breakpoints. The minimum inhibitory concentration for fosfomycin was evaluated by the MIC Test Strip method. A. urinae was encountered in cultures of 24 patients. The median patient's age was 72 years, and females slightly outnumbered males. Underlying diseases such as urologic disease, chronic lung disease, chronic kidney disease, heart disease, diabetes mellitus and dementia were found in 79.2% of patients. Two of the patients did not meet the criteria for a UTI. Susceptibility rates to penicillin, amoxicillin, meropenem, ciprofloxacin, levofloxacin, rifampicin, vancomycin, nitrofurantoin and fosfomycin were 100%, 100%, 100%, 83.3%, 79.2%, 100%, 100%, 95.8%, and 91.7%, respectively. Further surveillance studies and clinical trials are needed to confirm our data and to investigate the in vivo efficacy of the antimicrobial agents to treat UTIs by A. urinae.