The most important risk factor for NP is tracheal intubation; associated with a 3 to 21 fold risk [30] [31] [32] [33] . It increases the risk by; 1) causing sinusitis and trauma to nasopharynx (nasotracheal tube), 2) impairing swallowing of secretions, 3) acting as a reservoir for bacterial proliferation, 4) increasing bacterial adherence and colonization of airways, 5) requiring the presence of a foreign body that traumatizes the oropharyngeal epithelium, 6) causing ischemia secondary to cuff pressure, 7) impairing ciliary clearance and cough, 8) causing leakage of secretions around the cuff, and 9) requiring suctioning to remove secretions [34] . Microorganisms can adhere to the surface of the endotracheal tube and some species exude an exopolysaccharide that acts as a slime-like adhesive. That microbial biofilm on the tube surface provides a reservoir of microorganisms, and they are greatly resistant to the action of antimicrobials and host defence [35] . Also, the patient requiring MV exposes to other devices, such as nebulizers, humidifiers, which can be the source of microorganisms.