In vitro assessment of the probiotic potential and safety of lactic acid bacteria for aquatic animal health.

This study evaluated the in vitro probiotic-related properties and preliminary safety profiles of five lactic acid bacteria (LAB) strains for potential use in aquaculture: Limosilactobacillus reuteri ATCC 55730, Lentilactobacillus kefiri K107, Latilactobacillus sakei SN34, Lactiplantibacillus plantarum FI8595, and Streptococcus thermophilus BioSt64. Probiotic-related traits included antimicrobial activity against Lactococcus garvieae and Yersinia ruckeri, aggregation-related properties, and tolerance to fish bile and acidic conditions. Safety assessment included hemolytic and enzymatic activities and antibiotic susceptibility. Lmb. reuteri showed the strongest inhibition of L. garvieae (18.25 ± 1.06 mm), followed by S. thermophilus (9.85 ± 0.21 mm), whereas Ltb. sakei inhibited Y. ruckeri (9.00 ± 0.00 mm). All strains coaggregated with both pathogens and remained viable under the tested acidic and bile conditions. Lmb. reuteri and Lpb. plantarum showed high autoaggregation and cell surface hydrophobicity, which may indicate potential for intestinal adhesion, although this should be confirmed through direct adhesion assays. S. thermophilus showed the most favorable preliminary profile, combining antimicrobial activity, absence of detectable hemolysis, and susceptibility to most antibiotics under the conditions tested. Lmb. reuteri also showed promising probiotic-related properties, but its previously reported antimicrobial resistance determinants represent an important safety concern, while the β-hemolytic activity of Ltb. sakei precludes its selection without further assessment. Further controlled in vivo evaluation is required before any of these strains can be considered for use as aquaculture probiotics.