Antibacterial and Antibiofilm Potential of Sea Anemone (Stichodactyla haddoni) Isolated Vibrio (V. parahaemolyticus and V. alginolyticus), and Pseudoalteromonas (P. gelatinilytica and P. piscicida) Against Staphylococcus aureus and Pseudomonas aeruginosa

Background: Staphylococcus aureus and Pseudomonas aeruginosa are important human bacterial pathogens, which are resistant to several antibiotics. One of the main causes of their resistance is the ability of biofilm formation. Objectives: The present study aimed to evaluate the antibacterial and antibiofilm activity of the extracts of Vibrio parahaemolyticus, V. alginolyticus, Pseudoalteromonas gelatinilytica, and Pseudoalteromonas piscicida isolated from sea anemone (Stichodactyla haddoni) against S. aureus and P. aeruginosa. Methods: Four isolated bacteria were identified using biochemical and molecular identification methods, and their extracts were obtained by mixing the cell-free supernatants from their old broth culture using ethyl acetate and methanol as the solvents. The agar well-diffusion and micro-dilution methods were also applied to determine the antibacterial activity, minimum bactericidal concentration (MBC), and minimum inhibitory concentration (MIC) of the extracts. The ability of the extracts to inhibit biofilm formation and disrupt the preformed biofilm of the pathogens was attained through crystal violet staining in 96-well microtiter plates. To determine the nature of the extracts, they were exposed to protease enzyme, and the antibiofilm activity was compared with the untreated extracts. Results: The extracts of the four isolated bacteria inhibited bacterial growth and biofilm formation and disrupted the preformed biofilm of S. aureus (MIC = BIC = 600 µg/mL) and P. aeruginosa (MIC = BIC = 300 µg/mL). In addition, the active compounds of the extracts with antibiofilm activities were mainly proteases. Conclusions: According to the results, V. parahaemolyticus, V. alginolyticus, P. gelatinilytica, and P. piscicida had antibacterial and antibiofilm potential against S. aureus and P. aeruginosa, and their extract could also be further analyzed as an alternative to antibiotics.