Buccal cell carbohydrates are altered during critical illness

Cell-surface carbohydrates mediate the adherence of many pathogenic bacteria to epithelial cells. Because gram-negative bacteria adhere especially well to respiratory epithelial cells obtained from severely ill patients, we compared respiratory epithelial cell-surface carbohydrate levels of normal subjects with those of critically ill patients. Lectins were used to quantitate the amount of mannose, galactose, fucose, and sialic acid on buccal and tracheal cells. Fifteen critically ill patients, 20 normal subjects, and 10 minimally ill hospitalized patients were studied. The severely ill patients' buccal cells had decreased amounts of sialic acid and galactose. No differences were found between the normal and critically ill patients' tracheal-cell carbohydrates. The results obtained with a sialic acid-specific lectin were confirmed by direct measurement of buccal-cell sialic acid. We conclude that severely ill patients have decreased amounts of galactose and sialic acid on their upper-airway epithelial cells, and that loss of these two monosaccharides may explain the high prevalence of gram-negative bacterial colonization and pneumonia in the critically ill.