Investigation of the Antibacterial Effect of Astaxanthin and the Prevalence of Virulence and Antimicrobial Resistance Genes of Aeromonas spp.

In the study, in addition to the antibacterial effect of astaxanthin on Aeromonas hydrophila and A. sobria strains, the presence of virulence genes (Aero, act, ast, and hylA) and antibiotic resistance genes (tetC and sulI) in the strains was investigated. Antibiotic profiles of the strains were also investigated as part of the study. Strains were identified by conventional biochemical tests and PCR assay using a 16S rDNA primer pair specific for A. hydrophila. According to the results of bacteriological and molecular studies, two of the six Aeromonas strains were identified as A. hydrophila and four of them as A. sobria. The Aero virulence gene and the act virulence gene were found in all strains, while the ast and hylA virulence genes were detected only in A. hydrophila strains. All strains were resistant to chloramphenicol, tetracycline, nalidixic acid, and ampicillin in the standard disk diffusion test. Although all strains showed resistance to tetracycline and moderate resistance to oxytetracycline in the antibiogram tests, tetC antibiotic resistance gene was not detected in the strains and sulI antibiotic resistance gene was not detected in the strains. In the study, acetone solutions containing 0.1 g and 0.5 g of astaxanthin were found to have an antibacterial effect on A. hydrophila strains. Acetone solutions containing 0.1 g, 0.5 g, and 1.0 g of astaxanthin showed antibacterial effects on A. sobria strains. It was found that 0.1 g, 0.5 g, and 1.0 g astaxanthin solutions prepared with methanol and distilled water had no antibacterial effects on the strains.