Epidemiology and antimicrobial resistance patterns of Aeromonas species in Europe, 2020-2024 (AEuROMONAS)

Introduction: Aeromonas species are Gram-negative bacilli capable of causing bloodstream infections in both immunocompromised and otherwise healthy individuals. However, data on their epidemiology and antimicrobial resistance remain limited in Europe.Methods: We conducted a multicentre, retrospective, observational study that included all Aeromonas species isolates recovered from blood cultures in 56 European hospitals between January 1st 2020 and December 31st 2024. Epidemiological features and antimicrobial susceptibility profiles were analyzed.Results: A total of 590 Aeromonas isolates were included. Most were recovered from polymicrobial blood cultures (73.1%), and catheter-related bloodstream infections were frequent (21.7%). The most commonly reported species were A. caviae (30.1%), isolates without conclusive species identification (Aeromonas spp., 24.8%), A. hydrophila (20.7%), and A. veronii (19.1%). At the genus level, susceptibility to aztreonam, ceftazidime, and cefepime exceeded 90%. Resistance to fluoroquinolones (similar to 10%) and sulfamethoxazole/trimethoprim (up to 11%) was observed. Species-level analyses showed higher resistance rates to fluoroquinolones and sulfamethoxazole/trimethoprim among A. caviae and A. hydrophila, and increased resistance to ceftazidime among Aeromonas spp.Conclusions: Aeromonas species in Europe showed high susceptibility to ceftazidime and cefepime, alongside with emerging resistance to fluoroquinolones and sulfamethoxazole/trimethoprim. Species-specific findings should be interpreted cautiously due to limitations in routine identification methods, underscoring the need for sustained surveillance and harmonised diagnostic standards across Europe.