Comprehensive safety assessment of the probiotic Streptococcus salivarius OSTIA SALI-10

Rigid safety protocols are essential for the development of safe therapeutic agents, including probiotics. With the growing interest in probiotic use for oral health, it is crucial that these beneficial microorganisms adhere to stringent safety assessments, particularly concerning antibiotic resistance. In this study, we characterize Streptococcus salivarius OSTIA SALI-10, a novel strain isolated from the oral cavity of a healthy human adult and assess its safety profile through comprehensive genomic and phenotypic analyses. Although S. salivarius is generally considered a pioneer colonizer of the oral cavity and gastrointestinal tract, not all strains are classified as safe due to potential antibiotic resistance, hemolytic activities, or virulence factors. To address this, we developed a screening methodology that targets antibiotic-resistance genes in this species including resistance to macrolides and tetracyclines. SALI-10 demonstrated susceptibility to clinically relevant antibiotics, ensuring compliance with probiotic safety standards. Additional phenotypic characterization, including carbohydrate fermentation, enzyme profiling, hemolytic activity testing, and biogenic amine production, further reinforced its safety profile. Genomic analysis verified the absence of antibiotic resistance genes (ARGs), virulence factors, and mobile genetic elements (MGEs) associated with ARGs.