FIG. 2.

Survival of noncapsulated K. pneumoniae strains in the lungs of alveolar macrophage-depleted BALB/c mice. To deplete alveolar macrophages, 50 μl of either clodronate- or PBS-containing liposomes was inoculated intranasally 48 h before bacterial administration. Clodronate-containing liposome-treated mice and PBS-containing liposome-treated BALB/c mice were inoculated with 4 × 10⁴ CFU/mouse of the K50/n, K55/n, K2/n, and K21a/n Klebsiella strains. Mice were sacrificed 72 h after bacterial inoculation, the lungs were homogenized, and the CFU were counted. The controls consisted of mock infections without bacteria. The results are expressed as means and standards deviation calculated from two different experiments (sixanimals per group). Statistical differences (as determined by an ANOVA test) between the O1 and O3 serotypes were found for PBS-containing liposome-treated mice (P < 0.024). Also, statistical differences (as determined by the Student t test) were found between clodronate-containing liposome-treated mice and PBS-containing liposome-treated mice inoculated with the K50/n mannose-bearing O3-antigen K. pneumoniae strain (P = 0.001) and between clodronate-containing liposome-treated mice and PBS-containing liposome-treated mice inoculated with the K55/n mannose-bearing O3-antigen K. pneumoniae strain (P = 0.04). No differences were found between clodronate-containing liposome-treated mice and PBS-containing liposome-treated mice inoculated with O1-antigen K. pneumoniae strains.