Inhibition of Streptococcus mutans and S. sobrinus biofilms by liamocins from Aureobasidium pullulans

Authors: Leathers, Timothy; Rich, Joseph; BISCHOFF, KENNETH - Former ARS Employee; Skory, Christopher - Chris; Nunnally, Melinda

Submitted to: Biotechnology Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2018
Publication Date: 3/1/2019
Citation: Leathers, T.D., Rich, J.O., Bischoff, K.M., Skory, C.D., Nunnally, M.S. 2019. Inhibition of Streptococcus mutans and S. sobrinus biofilms by liamocins from Aureobasidium pullulans. Biotechnology Reports. 21:e00300. https://doi.org/10.1016/j.btre.2018.e00300.
DOI: https://doi.org/10.1016/j.btre.2018.e00300

Interpretive Summary: Streptococcus mutans and S. sobrinus grow as biofilms in dental plaque and are associated with dental caries. “Liamocins” are unique antimicrobials produced by the fungus Aureobasidium pullulans that recently have been found to have antibacterial activity with specificity for Streptococcus species. However, liamocins have not previously been tested for inhibition of strep biofilms. In this study, liamocins are shown to inhibit biofilm formation by S. mutans and S. sobrinus. This work will facilitate the development of liamocins as new antimicrobial agents.

Technical Abstract: The aim of this study was to determine if the novel anti-streptococcal inhibitors, liamocins, also inhibit biofilm formation by S. mutans and S. sobrinus. S. mutans strain ATCC 25175 and S. sobrinus strain ATCC 33478 were tested for biofilm formation in a rapid microtiter plate (MTP) assay and the effects of added liamocins were determined. This assay measures relative biofilm growth on pin lipids. Results were verified in a biofilm flow cell assay, using hydroxyapatite-coated coupons to simulate dental material. Planktonic cultures of S. mutans and S. sobrinus were inhibited by 0.1 mg liamocin/ml. When liamocins were added after the adhesion phase in a rapid microtiter plate assay, S. mutans was inhibited 53% by 5 mg liamocins/ml, while S. sobrinus was more sensitive, showing 100% inhibition at 0.5 mg liamocins/ml. When liamocins were added during the adhesion phase, biofilms of S. mutans showed 78% inhibition at 3.0 mg liamocins/ml. In a biofilm flow cell assay, liamocins added after the adhesion phase at 0.5 mg liamocins/ml inhibited biofilms of S. sobrinus, and appeared to remove biofilms over time. Liamocins were shown for the first time to inhibit biofilm formation by S. mutans and S. sobrinus. Since liamocins are specific for Streptococcus spp., they are potential new inhibitors of oral streptococcal biofilms that should not affect normal oral microflora.