The infections occurred during hospitalization are called hospital or nosocomial infections. These are the infections that develop 48 to 72 hours after hospitalization. They are a significant health and financial problem in almost all hospitals of the world. Hospital pneumonia is the second most common form of hospital infection, after urinary tract infections, and the leading cause of mortality. The most common complication in intensive care units is ventilator-associated pneumonia(VAP). The frequency of these infections, in patients treated in intensive care units, ranges from 20 to 70%, of which 80% are related to patients on mechanical ventilation, which is routinely carried out daily, in intensive care units. Ventilator-associated pneumonia(VAP) is defined as nosocomial pneumonia in patients who are on mechanical ventilation for more than 48 hours. A patient on a respirator is 6 to 21 times more likely to develop pneumonia, than the patients who are not on mechanical ventilation. The development of VAP prolonges patient's hospital time, time in the ICU, and significantly increases the cost of the treatments. In patients who develop VAP, the number of days on mechanical ventilation increases up to seven times, and the length of hospital stay is doubled. It is impossible to completely prevent the occurrence of VAP, but with proper prevention and treatment, it can be reduced.