A patient develops VAP (ventilator-associated pneumonia) on day 8 of mechanical ventilation. BAL quantitative culture grows >104 CFU/mL of Pseudomonas aeruginosa. The primary pathogenesis of VAP involves:

• A Haematogenous seeding of lung parenchyma from a distant infected site
• B Airborne transmission of organisms directly via the ventilator circuit
• C Contiguous spread from pleural empyema
• D Micro-aspiration of oropharyngeal secretions colonised with nosocomial pathogens around the endotracheal tube cuff ✓

Explanation

VAP pathogenesis primarily involves micro-aspiration of subglottic secretions pooling above the endotracheal tube cuff; oropharyngeal flora shifts to gram-negative pathogens within 24–48 hours of ICU admission, providing the inoculum. Ventilator circuits rarely serve as primary pathogen sources if properly maintained. Prevention strategies (HOB elevation 30–45°, oral decontamination with chlorhexidine, subglottic secretion drainage, cuff pressure monitoring) directly target this mechanism. Quantitative BAL culture >104 CFU/mL distinguishes VAP from colonisation.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.