| Abstract |
Lactoferrin, a natural iron-binding protein found in tears, possesses antimicrobial properties that may help combat colonisation of the ocular surface by pathogens such as Pseudomonas aeruginosa. This study examined how human lactoferrin affects P. aeruginosa adhesion, biofilm formation, and entry into corneal cells. Human lactoferrin antimicrobial, anti-biofilm, and anti-invasion effects against six P. aeruginosa strains were measured using minimum inhibitory concentration microdilution assays, crystal violet biofilm inhibition and degradation assays, and viable colony counts. Its ability to protect human corneal epithelial cells from bacterial invasion was tested using a gentamicin protection assay, while effects on bacterial motility were measured with a twitching assay. Data were analysed using unpaired t-tests with significance set at p ≤ 0.05. Lactoferrin showed strong inhibition and dispersal activity against six strong biofilm-forming P. aeruginosa strains (PA008, PA016, PA216, PA225, PA232, and ATCC19660). On average, lactoferrin inhibited biofilm formation by ≥ 75%, with 2 mg/mL causing the greatest reduction in biofilm biomass and viable cells. Lactoferrin degraded ≥60% of biofilm formed by P. aeruginosa. Lactoferrin also significantly reduced bacterial attachment and invasion (reduced by ≥ 80%; p = 0.01) into human corneal epithelial cells. Overall, these findings demonstrate that human lactoferrin inhibits P. aeruginosa biofilm development, disrupts established biofilms, and limits bacterial adhesion and invasion of corneal epithelial cells. This underscores its action as a natural antimicrobial and may be one reason why the ocular surface is paucimicrobial.
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