Environmental Reservoirs of Antimicrobial Resistance in Captive Aquatic and Avian Wildlife: Evidence from a One Health Perspective

Antimicrobial resistance (AMR) has emerged as one of the most pressing global health challenges, affecting human, animal, and environmental health. Captive wildlife facilities, including aquariums and zoological institutions, provide unique ecological settings where close interactions among animals, humans, and shared environments may facilitate the maintenance and dissemination of antimicrobial-resistant microorganisms. This study evaluated the occurrence, antimicrobial susceptibility patterns, and genetic determinants of extended-spectrum β-lactamase (ESBL)-producing Gram-negative bacteria among captive aquatic animals and birds housed in an aquarium in Abu Dhabi, United Arab Emirates, representing the first investigation of its kind in the region. A total of 60 samples, including rectal swabs, fecal specimens, water samples, and feeding-station environmental samples, were collected during 2024. Isolation of cefotaxime-resistant Gram-negative bacteria was performed using selective MacConkey agar supplemented with cefotaxime. Antimicrobial susceptibility profiles were determined using the Kirby–Bauer disk diffusion method, while phenotypic confirmation of ESBL production was conducted using the double-disc synergy test. Molecular characterization was performed by PCR targeting major β-lactamase genes (bla_CTX-M, bla_SHV, bla_OXA, and bla_TEM), with further classification of CTX-M-positive isolates into phylogenetic groups. The majority of isolates exhibited multidrug-resistant phenotypes, with particularly high resistance to β-lactam antimicrobials. More than 70% of isolates were confirmed as ESBL producers. Among the resistance determinants detected, bla_SHV was the predominant ESBL-associated gene, whereas CTX-M group 1 was the most frequently identified CTX-M variant. The detection of multidrug-resistant and ESBL-producing bacteria in animals and environmental samples highlights the potential persistence and circulation of resistant microorganisms within captive aquatic ecosystems. These findings emphasize the importance of captive wildlife facilities as potential environmental reservoirs of AMR and underscore the need for integrated surveillance, enhanced biosecurity measures, and prudent antimicrobial stewardship. Adopting a One Health approach is critical to reducing the risk of antimicrobial resistance transmission across human, animal, and environmental interfaces and to supporting sustainable wildlife management practices.