Excess Mucin Impairs Subglottic Epithelial Host Defense in Mechanically Ventilated Patients

Area of Science:

• Critical care medicine
• Infectious disease
• Pulmonology

Background:

• Ventilator-associated pneumonia (VAP) is caused by aspirating infected secretions from the subglottic area in mechanically ventilated patients.
• Understanding subglottic colonization mechanisms is crucial for developing targeted VAP prevention strategies.

Purpose of the Study:

• To characterize subglottic host defense dysfunction in intensive care unit (ICU) patients on mechanical ventilation.
• To investigate the role of subglottic mucin in neutrophil phagocytic impairment and bacterial growth.

Main Methods:

• Prospective subglottic sampling in ICU patients and newly intubated controls.
• Isolation and culture of primary subglottic epithelial cells.
• Laboratory analysis of host innate immune defenses and secretion properties.

Main Results:

• ICU patients exhibited reduced subglottic microbiological diversity and increased respiratory pathogens.
• Subglottic secretions showed neutrophilic inflammation, elevated cytokines/proteases, and mucin accumulation.
• Subglottic mucin impaired neutrophil phagocytosis and bacterial killing, an effect reversible with mucolytics.
• Mucus promoted bacterial growth and invasion in a human subglottic epithelium model.

Conclusions:

• Mechanical ventilation induces mucin secretion and inflammation, impairing neutrophil function and promoting bacterial growth.
• Mucolytic agents can reverse mucin-induced neutrophil dysfunction.
• Enhanced mucus disruption and removal may improve VAP prevention alongside subglottic drainage.