Comparative Effects of Cigarette Smoke and Heated Tobacco Product Aerosols on Biofilm Production by Respiratory Pathogens

Biofilms are involved in both acute and chronic respiratory infections. While cigarette smoke extract (CSE) has been shown to increase biofilm formation by certain respiratory pathogens, the impact of emerging heated tobacco products (HTPs) remains unclear. We compared the effects of CSE with two HTP aerosol extracts on biofilm biomass and metabolic activity of common respiratory pathogens. Reference strains of <i>Staphylococcus aureus</i>, <i>Pseudomonas aeruginosa</i>, <i>Klebsiella pneumoniae</i>, <i>Streptococcus pneumoniae</i>, and non-typeable <i>Haemophilus influenzae</i> (NTHi), known respiratory pathogens, were grown as 24 h biofilms in 96-well plates (48 h for <i>S. aureus</i> and <i>P. aeruginosa</i>). These were exposed to CSE and HTP extracts from iQOS™ (Terea™ Turquoise, ILUMA™ device) and glo™ (neo™ Azure, HyperPro™ device), prepared in liquid culture media. Biofilm density was quantified by the crystal violet assay. Metabolic activity (planktonic and biofilm) was assessed by MTT reduction to formazan. At 24 h, CSE markedly reduced <i>H. influenzae</i> biomass versus iQOS™, glo™, and control, while <i>K. pneumoniae</i>, <i>S. aureus</i>, and <i>P. aeruginosa</i> showed no significant biomass differences. At 48 h, CSE significantly increased biomass in <i>P. aeruginosa</i> and <i>S. aureus</i> versus other exposures. Biofilm MTT assay measured metabolic activity increased in CSE exposure for <i>K. pneumoniae</i> versus iQOS™ and control, and for <i>S. aureus</i> versus control. Overall, HTP extracts showed limited, inconsistent effects compared with CSE, indicating combustion-derived constituents more strongly promote biofilm maturation in this model.