IADR Abstract Archives
Antimicrobial and Antiviral Activity of Hexylresorcinol Lozenges Against Oropharyngeal Pathogens
Objectives: The substituted dihydroxybenzene, hexylresorcinol (HR) is routinely used in mouthwashes and lozenges for the relief of sore throats in upper respiratory tract infections due to its anaesthetic/antiseptic properties. Although the in vitro antimicrobial activity of HR (Strepsils® lozenges) was recently defined against planktonic bacteria, this does not directly relate to effectiveness in vivo as, bacteria exist in highly structured biofilm communities within the oropharynx. Hence, direct evidence of HR bactericidal and virucidal activity in lozenge formulations is limited.
Methods: In vitro antimicrobial activity of HR (pure or directly released from Strepsils® lozenges) was determined by dissolution in Mueller-Hinton [MH] broth or Artificial Saliva [AS] against a library of 41 (reference and clinical) bacterial and fungal pathogens using minimum inhibitory concentration (MIC) and Log10 reduction assays. Antiviral activity against SARS-CoV-2 and Influenza virus was determined by suspension test (EN14476). Antibiofilm activity was determined using minimum biofilm eradication concentration (MBEC) assays, as well as confocal laser scanning microscopy (CLSM) and COMSTAT image analysis of established (24 h) biofilms.
Results: HR exhibited MICs ≤64 µg/mL against 28/41 organisms. High lozenge antimicrobial activity (> 3log10; >99.9% reduction) was observed within 10 mins (Blackcurrant) and 30 mins (Honey & Lemon) in 9/10 test strains. Log10 reductions in infectivity were observed for HR against SARS-CoV-2 (>3) and influenza virus (>1.5) at 20 mins. 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 (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).
Conclusions: The antimicrobial activity of HR was demonstrated at concentrations >10X lower than that in marketed lozenges, highlighting its potential usefulness in the management of oropharyngeal infections.
Methods: In vitro antimicrobial activity of HR (pure or directly released from Strepsils® lozenges) was determined by dissolution in Mueller-Hinton [MH] broth or Artificial Saliva [AS] against a library of 41 (reference and clinical) bacterial and fungal pathogens using minimum inhibitory concentration (MIC) and Log10 reduction assays. Antiviral activity against SARS-CoV-2 and Influenza virus was determined by suspension test (EN14476). Antibiofilm activity was determined using minimum biofilm eradication concentration (MBEC) assays, as well as confocal laser scanning microscopy (CLSM) and COMSTAT image analysis of established (24 h) biofilms.
Results: HR exhibited MICs ≤64 µg/mL against 28/41 organisms. High lozenge antimicrobial activity (> 3log10; >99.9% reduction) was observed within 10 mins (Blackcurrant) and 30 mins (Honey & Lemon) in 9/10 test strains. Log10 reductions in infectivity were observed for HR against SARS-CoV-2 (>3) and influenza virus (>1.5) at 20 mins. 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 (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).
Conclusions: The antimicrobial activity of HR was demonstrated at concentrations >10X lower than that in marketed lozenges, highlighting its potential usefulness in the management of oropharyngeal infections.