The transiency of oropharyngeal colonization with gram-negative bacilli in residents of a skilled nursing facility.

To determine the duration and persistence of gram-negative bacillary (GNB) oropharyngeal colonization over a specified period and the risk of subsequent GNB pneumonia developing in nursing home patients, we prospectively cultured for 31 weeks the oropharynges of patients in a skilled nursing facility. Over a 31-week period, an average of 13.8 percent of the patients showed colonization (weekly prevalence rates ranged from 0 to 29 percent). No patient had pneumonia during the study period. We concluded that the presence of GNB in the oropharynx of our patients is transient, continually changing over an extended period, and that GNB colonization as a transient occurrence is not directly associated with an increased risk of GNB pneumonia. Our data also emphasize the limitations of previously described single-culture survey studies in predicting the importance of GNB oropharyngeal colonization.