Aims: The substituted dihydroxybenzene, hexylresorcinol (HR), with anaesthetic and antiseptic properties, is routinely used in mouthwashes and lozenges for the relief of oropharyngeal conditions. Although the in vitro antimicrobial activity of HR (Strepsils® lozenges) has recently been defined against planktonic bacteria, it does not necessarily relate to effectiveness in vivo as, within the oropharynx, bacteria exist in complex, highly structured, 3-dimensional biofilm communities.

Methods: To determine potential utility of HR against biofilms in oral disease, antibiofilm activity was characterised against a range of oropharyngeal pathogens including: Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Streptococcus pyogenes and Candida albicans using minimum biofilm eradication concentration (MBEC) assays. Direct antibiofilm effects were studied using confocal laser scanning microscopy (CLSM), LIVE/DEAD staining and COMSTAT image analysis of established (24 h) biofilms.

Results: MBECs were up to 7-fold higher than the observed MICs (minimum inhibitory concentrations).  CLSM revealed HR induced significant concentration-dependent biofilm disruption in S. pyogenes at 64 µg/ml, with significant decreases in bio-volume (p<0.05) and cell viability (i.e. increased LIVE/DEAD cell ratio; p<0.05).  Importantly, HR demonstrated anti-biofilm activity at concentrations 3-fold lower than those attained following dissolution of lozenges in artificial saliva (500 µg/ml).

Conclusion: These results highlight for the first time, that the anti-biofilm activity of HR lozenges could be beneficial in the management of biofilms associated with oropharyngeal infection/inflammation.