Antibiotic Resistance Profiles and Biochemical Characterization of Bacteria Isolated from Gökçeada Salt Lake Lagoon (Çanakkale) Sediment Samples

Gökçeada Salt Lake Lagoon in Çanakkale, Türkiye, is a hypersaline environment that supports halophilic bacterial communities. This study examined the antibiotic susceptibility of 60 bacterial isolates obtained from four seasonal sediment samples. Morphological and biochemical characterization of the isolates included Gram staining, indole production, nitrate formation tests, and elemental analysis using ICP-OES. Antibiotic resistance was assessed via the disk diffusion method using seven antibiotics: Novobiocin (5 μg), Erythromycin (15 μg), Streptomycin (10 μg), Bacitracin (10 μg), Penicillin G (10 μg), Ampicillin (10 μg), and Tetracycline (30 μg). ICP-OES results showed elevated S, Ca, Mg, Na, and Fe concentrations, particularly in April 2024. The Multiple Antibiotic Resistance (MAR) index exceeded 0.2 in all isolates, with the highest value (0.7142) also detected in April 2024. The Shapiro-Wilk test indicated non-normal distribution of MAR values; thus, the Kruskal-Wallis test was used for statistical analysis. Although no significant difference was found between sampling periods (p > 0.05), seasonal increases in resistance suggest gradual adaptation. The consistently high MAR indices point to ongoing anthropogenic pressure, likely due to tourism, agriculture, and livestock activities in the region. This persistent exposure may drive resistance development in microbial populations. The findings underscore the importance of monitoring antibiotic resistance in halophilic bacteria, as such resistance may pose public health risks through environmental pathways.