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The present is a descriptive study aimed at an investigtion into the incidence of bacterial infections in the respiratory system of infans under mechanical ventilation. Use of this instrument is inevitable in cases of respiratory failure or delay, and the air passage should be kept clean by means of a trachea suction thus the problem of pulmonary infection due to handling and entering of particles from the environment to the lungs may not be ignored. In this research, 756 culture samples were prepared from 27 subject infant (one day to 12 months old), in four stages from the onset of setting the tube in the trachea, in a period of 24 hours at senen locations for suction on the patient, including pulmonary secretions, oral secretions, the suction agent's hands, the suction catheter, the adhesive tape used for fixing the trachea tube, normal saline solution and connection between the catheter and the suction tube. Out of 27 infants, ten of them (37%) stayed alive until the end of 72 hours, and 17 of them (63%) passed away, the death of Jive (29%) of whom was inevitable in view of the illness diagnosis but 12 (70%) of them were those whom the mechanical ventiltor could have prevented from dying.The research findings report the results of cultures of samples from infants who stayed alive until each of the foursome stages and which were, respec tively,27,25, 22 and 10 in number, as follow:The result of culturing pulmonary secretions of the infants in foursome stages respectively reported contaminations of 27%, 52%, 77.3% and 100%.A comprehensive investigation shows that in more that 50% of cases, these tools may transfer microorganisms to the patient and such death and 100% contamination of pulmonary and oral secretions of the patient at the fourth stage of sampling are justified. The various types of microorganisms observed during this research.Which Could be harmful, when there microorganisms enter into the resperatory tract of patiento.