One Health Surveillance of Antimicrobial Resistance in the Eastern Mediterranean: The Blackchin Guitarfish as a Case Study

Antimicrobial resistance (AMR) poses a global One Health challenge, linking human, animal, and environmental health. Marine environments and organisms are increasingly recognized as reservoirs of antimicrobial-resistant bacteria and mobile genetic elements. This study investigates the prevalence of antibiotic non-susceptible bacteria and resistance genes in juvenile Glaucostegus cemiculus blackchin guitarfish along the Israeli Mediterranean coast. Between 2023 and 2024, 19 specimens were sampled from Ma'agan Michael, Acer, and Evtach. Swabs from skin, gills, and mouth were cultured on selective and chromogenic media, followed by identification using matrix-assisted laser desorption/ionization—time-of-flight (MALDI-TOF MS) and antimicrobial susceptibility testing. Resistance genes were screened by quantitative PCR (qPCR), with CTX-M beta-lactamases (bla_CTX-M) variants sequenced and phylogenetically analyzed. A total of 162 bacterial isolates were obtained, of which 54% were identified to 26 species across eight families, primarily Staphylococcaceae (39%) and Bacillaceae (36%). Several clinically relevant pathogens were detected, including Staphylococcus aureus, Pseudomonas spp., and Escherichia coli. Reduced susceptibilities were observed in 31 isolates from 10 specimens, with multidrug resistance identified in P. mendocina, P. stutzeri, and E. coli. Skin samples yielded the highest proportion of resistant isolates. Importantly, the bla_CTX-M-185 extended-spectrum β-lactamase gene was detected in six individuals, with sequences closely related to those of human-associated strains, suggesting anthropogenic origins. These findings demonstrate that juvenile guitarfish harbor clinically significant resistant bacteria and genes, highlighting the marine environment as a potential reservoir of AMR. Integrating endangered species into AMR surveillance highlights the importance of for environmental monitoring and conservation strategies within a One Health framework.