Comparative in vitro antibacterial screening of Linckia laevigata and Archaster typicus ethanol extracts against Bacillus cereus, Streptococcus mutans, and Vibrio parahaemolyticus

Abstract

Background: The increasing prevalence of antimicrobial resistance (AMR) has become a major challenge in veterinary medicine, aquaculture, and public health, creating a growing need for alternative antimicrobial compounds from natural resources. Marine echinoderms, particularly starfish, are recognized as promising sources of structurally diverse secondary metabolites with antibacterial potential. Aim: This study comparatively evaluated the in vitro antibacterial activity of ethanol extracts from two Indonesian starfish species, Linckia laevigata and Archaster typicus, against clinically and aquaculture-relevant bacterial pathogens. Methods: Starfish samples were collected from Suli waters, Central Maluku, Indonesia. Extracts were obtained using maceration with 96% ethanol. Antibacterial activity was tested using the disc diffusion method against Bacillus cereus, Streptococcus mutans, and Vibrio parahaemolyticus. Extract solutions were prepared at concentrations of 250, 500, 750, and 1000 mg/mL using DMSO as the solvent. Amoxicillin (10 µg/disc) and DMSO were used as controls. All assays were performed in duplicate (n = 2). Data were analyzed descriptively. Results: Both starfish extracts demonstrated antibacterial activity against all tested bacterial species. The inhibition zones ranged from 13.73 ± 3.64 mm to 27.00 ± 0.71 mm. The highest inhibition zone of L. laevigata extract was observed against B. cereus at 1000 mg/mL (25.70 ± 0.85 mm), whereas A. typicus extract produced the largest inhibition zone against B. cereus at 500 mg/mL (27.00 ± 0.71 mm). The extracts generally showed greater inhibition against the tested Gram-positive bacteria than against V. parahaemolyticus. Due to the limited number of replicates (n = 2), the results were interpreted descriptively. Conclusion: Ethanol extracts from L. laevigata and A. typicus exhibited preliminary antibacterial activity against foodborne, oral, and aquatic bacterial strains. These findings provide baseline evidence supporting further investigation of Indonesian starfish extracts as potential sources of marine-derived antibacterial compounds for aquaculture, food safety, and related biomedical research.