Infection begins with bacterial attachment to host cells. Studies have shown a significant correlation between the attachment of bacteria to human pharyngeal epithelial cells and the occurrence of respiratory tract infections.

The present study identified the receptor on human pharyngeal epithelial cells that mediate binding Moraxella catarrhalis and Haemophilus influenza. In an attempt to prevent the occurrence of infections, the study investigated the effects of povidone-iodine gargling on the incidence of respiratory infections. 

• It enrolled 23 adult male and female patients with chronic respiratory diseases showing repeated infections.
• Patients had to gargle more than four times/day with povidone-iodine gargle over extended periods, i.e., from several months up to over two years.
• It found a significant decrease in the incidence of episodes of acute exacerbation of chronic respiratory infections compared to before the use of povidone-iodine gargle.
• Also, there was a 50% reduction in the episodes of infections with Pseudomonas aeruginosa, Staphylococcus aureus (including MRSA), and H. influenza. 

The results of this study confirm the effectiveness of povidone-iodine gargle in significantly reducing the incidence of acute exacerbations of chronic respiratory disease. The authors assume the reason may be that the povidone-iodine gargle destroys the colonized bacteria, and thus infection does not occur. Therefore, povidone-iodine gargle may be employed in such patients as a preventive therapy. Further studies must determine this drug′s mechanism of action to prevent respiratory tract infections.

Source: Nagatake T, Ahmed K, Oishi K. Prevention of respiratory infections by povidone-iodine gargle. Dermatology. 2002;204 Suppl 1:32-6. doi: 10.1159/000057722. PMID: 12011518.