Intubation and mechanical ventilation lead to an extensive expansion of VAP-associated bacterial species in respiratory secretions of ventilated pigs

Summary

This experimental study used a pig model of mechanical ventilation to characterise the kinetics and species composition of bacterial colonisation in the respiratory tract following intubation and ventilation for up to three days. Gram-negative bacteria expanded dramatically in secretions pooled above the endotracheal tube cuff within 24 hours, with species including Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterobacteriaceae—organisms commonly implicated in human ventilator-associated pneumonia. The findings suggest that accumulation of bacteria above the cuff may be a critical precursor to VAP development.

Regional applicability

This is a mechanistic animal model study examining critical-care-associated infection pathophysiology in humans, not a farming or food production system study. Its findings are relevant to human intensive-care practice globally, but not directly applicable to United Kingdom farming systems, soil health or agricultural food production.

Key measures

Colony-forming units per millilitre (CFU/ml) of Gram-negative bacteria in respiratory secretions; bacterial species identification by 16S-RNA gene sequencing; timing of colonisation (days 0–2 post-intubation)

Outcomes reported

The study quantified Gram-negative bacterial colonisation of the respiratory tract in mechanically ventilated pigs over 48 hours, using culture-based enumeration and 16S-RNA sequencing to identify species. Bacterial counts increased dramatically above the endotracheal tube cuff, from median 7.3×10³ at intubation to 2.0×10⁷ at day 1 and 3.2×10⁷ at day 2.

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