The initial stage of infection pathogenesis involves bacterial attachment to host cells. Studies have demonstrated a notable correlation between bacterial attachment to human pharyngeal epithelial cells and the occurrence of respiratory tract infections. Human pharyngeal epithelial cells possess receptors that facilitate the binding of bacteria like Moraxella catarrhalis and Haemophilus influenzae.

The present study investigated the preventative effects of povidone-iodine gargling on respiratory infections in 23 adult patients experiencing recurrent infections due to chronic respiratory diseases. Over an extended period, ranging from several months to over two years, patients were instructed to gargle with povidone-iodine more than four times a day.

The study observed -

• A significant decrease in the incidence of acute exacerbations of chronic respiratory infections following the use of povidone-iodine gargle. 
• Episodes of infections involving Pseudomonas aeruginosa, Staphylococcus aureus (including MRSA), and H. influenzae were reduced by half. 

The results of this study suggest that povidone-iodine gargle is effective in substantially lowering the occurrence of acute exacerbations in chronic respiratory diseases. This efficacy may be attributed to the destruction of colonized bacteria, preventing the onset of infection. 

Hence, povidone-iodine gargle could be considered as a preventive therapy for patients experiencing recurrent infections due to chronic respiratory diseases.

Reference-

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