The Effect of Lactoferrin on Oral Bacterial Adhesion

Lactoferrin (LF), an iron-binding glycoprotein, plays an important role in human innate defense against local mucosal infection. Although LF interference with bacterial aggregation and biofilm development has been demonstrated in Pseudomonas aeruginosa, limited studies have been conducted on its effect on oral biofilm formation. We hypothesized that LF interferes with initial oral bacterial attachment to surfaces by iron sequestration, thus inhibiting subsequent biofilm development. Objective: To investigate the effect of Lf on early stages of single and multi- species oral biofilm development. Methods: Streptococcus gordonii (Sg), Streptococcus mutans (Sm), Fusobacterium nucleatum (Fn) and Porphyromonas gingivalis (Pg) were used in this study. Glass coupons of a two-track flowcell perfused with artificial saliva (0.3ml/min) with and without LF (100µg/ml) were used for studying initial bacterial attachment (3hr, 37^oC). Single or multi-species test bacteria (10⁷cfu/ml) were also added to glass slides precoated with LF or lactoglobulin (LG) (20-100µg/ml) for 30min at 37^oC, gently rinsed, and stained with BacLight Live/Dead probe. Images of the attached bacteria were analyzed (Image-Pro Plus, version 5.1) and total attachment of test bacteria was determined. Bacterial attachment in the presence of an iron chelator, 2,2'-dipyridyl (25-100µg/ml) was also examined. Results: LF significantly reduced the initial attachment of Sg (50.3%), Sg/Fn (48.7%) and Sg/Pg (62.1%) compared to the control (p<0.05). However, the attachment of Fn and Pg was not affected by LF. In the presence of 100mM 2,2'-dipyridyl, attachment of Sg was reduced by 53.87%. LF did not inhibit Sg attachment in the presence of FeCl₃ (20-200µM). LG did not affect the attachment of Sg. Conclusion: Lactoferrin suppresses initial attachment of Sg and Sg coaggregates by iron sequestration. This may lead to subsequent inhibition of oral biofilm development (Supported by the US Army Dental and Trauma Research Detachment Great Lakes, IL).