Semi-Aquatic Turtles as Potential Reservoirs for Resistant and Virulent Aeromonas spp.

Semi-aquatic turtles are popular companion animals and represent an important One Health interface in Portugal due to their potential to harbour zoonotic pathogens. This study aimed to characterize the virulence and antimicrobial resistance (AMR) profiles of Aeromonas spp. isolated from captive semi-aquatic turtles in Portugal. Cloacal swabs (n = 31) were collected from turtles under human care, and Aeromonas spp. were isolated using selective media and identified by multiplex PCR. Antimicrobial susceptibility was assessed by disk diffusion using eleven antibiotics, while the phenotypic virulence profile was evaluated by determining isolates’ ability to express five hydrolytic enzymes and to form biofilm. A total of 86 Aeromonas isolates were recovered, with A. hydrophila being the most prevalent (77.9%). Most isolates displayed high pathogenic potential: over 87% produced DNase, haemolysin, and lecithinase, while nearly all produced protease and gelatinase. Also, 44.2% of the isolates were resistant to at least one antibiotic, and 12 (14.0%) were multidrug resistant. Higher Multiple Antibiotic Resistance (MAR) indices were significantly associated with turtles housed in indoor aquariums (p < 0.05). These findings indicate that captive semi-aquatic turtles may act as reservoirs of virulent and antimicrobial-resistant Aeromonas spp., highlighting potential zoonotic risks and supporting the need for a One Health approach in their management.