ObjectiveTo determine whether or not the presence of a nasogastric tube causes a change in the bacterial flora in the oropharynx.Study DesignCohort (prospective) design with concurrent control.SettingGeneral Surgical and Ear, Nose, and Throat Units of a tertiary care hospital.PatientsSixteen patients with and 14 patients without a nasogastric tube.InterventionsPatients scheduled to undergo surgery under general anesthesia with endotracheal intubation were eligible for inclusion in the study. From these patients, a study cohort of 16 consecutive patients who were to have nasogastric tube intubation and 14 patients who were not to have nasogastric intubation were enrolled. All patients had a high oropharyngeal swab taken for bacteriologie culture just before surgery. The swab of the oropharynx for culture was repeated after 48 to 72 hrs. The type of organism grown was identified and compared between and within the two groups.ResultsThere was a significant increase in the frequency of colonization of the oropharynx by pathogenic Gram-negative bacteria after 48 to 72 hrs of nasogastric intubation in comparison with the preintubation level (p< .01) as well as in comparison with the group that did not have nasogastric intubation (p< .001). The pathogens included Pseudomonas, Klebsiella, Proteus andEscherichia coli.There was also a tendency for suppression of normal flora. There was no significant change in the flora of the control group of patients who did not have nasogastric intubation. The two groups were comparable with respect to age, gender, severity of underlying illness, and use of prophylactic perioperative antibiotics.ConclusionsThe presence of nasogastric tubes in patients predisposes to colonization by Gram-negative pathogenic bacteria within 48 to 72 hrs.