Synergistic Interaction Between Lactoferrin and Low-Dose Antibiotic Against Fusobacterium nucleatum Associated With Periodontal Disease

Background: Periodontitis is a chronic inflammatory disease characterized by the progressive destruction of periodontal tissues, significantly impacting oral and systemic health. Fusobacterium nucleatum (Fn) plays a key role in disease pathogenesis due to its interactions with other periodontal pathogens. Lactoferrin (LF), a multifunctional glycoprotein, has demonstrated antimicrobial and anti-inflammatory properties, but its effects in combination with antibiotics against Fn are not fully understood. Objective: To evaluate the antibacterial activity of bovine lactoferrin (bLF), in combination with low concentrations of penicillin-streptomycin, against F. nucleatum , and to assess its potential as an adjunctive therapeutic strategy in periodontitis. Methods: Bovine lactoferrin (bLF) was prepared at a concentration of 20 mg/mL in sterile distilled water. The dual antibiotic solution (penicillin–streptomycin) was adjusted to a final concentration of 0.604 µg/mL. For the combination treatment, 10 µL of the antibiotic solution was added to 1 mL of the bLF solution, yielding a final antibiotic concentration of approximately 0.003 µg/mL. This combination, along with antibiotic-only and control groups, was tested in vitro against Fusobacterium nucleatum (ATCC 25586) cultured under anaerobic conditions at 37°C. Bacterial growth was assessed by optical density (OD₆₀₀) measurements and colony-forming unit (CFU) enumeration. Controls included bacteria without lactoferrin or antibiotics. Results: Lactoferrin significantly inhibited bacterial growth in a dose-dependent manner. Low-concentration antibiotics alone had negligible antibacterial effects, with bacterial growth comparable to controls (p > 0.05). The combination of lactoferrin with antibiotics enhanced bacterial inhibition, indicating a synergistic effect. Conclusions: Bovine lactoferrin, particularly in combination with sub-therapeutic antibiotic concentrations, shows promising antibacterial activity against F. nucleatum, suggesting its potential as an adjunctive agent in periodontitis management. These findings warrant further in vivo studies to confirm efficacy and explore clinical applications.