Objectives: The aim of this study was to investigate the incidence of ventilator associated pneumonia (VAP) in 140, ICU patients with oral preventive probiotics in the treatment group and the placebo in the control group. Research design: A randomized, double-blind, respective study. Inclusion criteria: age of eighteen years and above, the consent of relatives, patients with tracheal intubation and mechanical ventilation which will be continued to the next 72 hours, patients' intubation must not be for more than 48 hours, starting patients' feeding until 24 hours. Exclusion criteria: pregnancy, weakened immune system due to any reason, suppressor of the immune system, replacement heart valves, vascular grafts, heart trauma, history of rheumatic fever, endocarditis, congenital anomaly of heart, injury of stomach, esophagus, bowel, injury to airway, pancreatitis and base skull fracture . Sample Size: 140 patients found eligible based on the inclusion criteria. Interventions: intervention group received probiotics capsule once daily and in the control group, placebo once daily were used. While, Staphylococcus aureus, Pseudomonas and Klebsiella, Acinetobacter were the most common bacteria
and the diagnosis of VAP will be based on the culture of sputum culture of BAL. Intervention time: immediately after admission of the qualified patients into the study.