Fig. 4.

Effect of complete-core oligosaccharide on P. aeruginosa infection in neonatal mouse lungs. Each point indicates the median bacterial CFU for 8 to 10 lungs obtained from each group of mice and the bars indicate the upper and lower quartiles. Inhibitor delivered with inoculum: (●), none; (□), complete-core oligosaccharide; and (■), incomplete-core oligosaccharide. Groups of 7-day-old neonatal BALB/c mice were infected intranasally with ~ 10⁸ CFU of strain PAO1 (14) alone or mixed with either complete-core oligosaccharide (50 μg) or incomplete-core oligosaccharide (50 μg) (11). After 1, 24, or 48 hours, four to five mice were killed and their lungs were removed, weighed, and dispersed into single-cell suspensions. The total CFU of bacteria present in each lung was determined from a sample treated with Triton X-100 (0.5%) to release intracellular bacteria. The remaining cells were treated with gentamicin (300 μg/ml) for 60 min to kill extracellular P. aeruginosa, then the cells were centrifuged, washed twice in tissue-culture medium, and resuspended in 200 μl of 0.5% Triton X-100 to release intracellular bacteria. These suspensions were diluted and plated. Differences among groups were analyzed by nonparametric statistics: P < 0.0001, Kruskall-Wallis nonparametric ANOVA; P < 0.001, Dunn procedure for individual pair-wise differences between the groups at 1 and 24 hours. Also, at 1 hour the group receiving the incomplete-core oligosaccharide had a reduced amount (P = 0.05, Dunn procedure) of intracellular bacteria compared with the group receiving nothing with the inoculum. At 48 hours, the group treated initially with complete-core inhibitor had significantly more bacteria in their lungs (P = 0.003, Kruskall-Wallis; P < 0.05, Dunn procedure for all pair-wise comparisons) than did the other groups.