(A–C) The illustration in A shows the experimental design of the confocal imaging studies of bacterial clearance shown in B and C. As indicated in A, mice were given intranasal instillations of SA^GFP, then the lungs were excised for live imaging 10 minutes later. Confocal images (B) and group data (C) show microaggregates (arrows; MA) and small clusters (arrowheads; SC) of GFP-expressing S. aureus (SA^GFP) in live alveoli of intact, perfused lungs of LMC or AT1-CFTR^null mice as indicated. Calcein red-orange (CR) dye was added to the perfusate solution to delineate alveolar walls (insets). Images included at least 30 alveoli and were generated in the same location at 1 and 4 hours after instillation. In the 4-hour images, magenta arrows and arrowheads point out the initial locations of microaggregates and small clusters that were displaced during the imaging period or were not found in the 4-hour images. White arrows and arrowheads in the 4 -hour images indicate microaggregates and small clusters that did not change. In C, circles indicate n and each represent the change of all small clusters or microaggregates present in one imaging field from 1 to 4 hours after i.n. SA^GFP instillation. Imaging fields were generated in the lungs of 3 LMC and 3 AT1-CFTR^null mice. Since imaging fields had to be excluded from the analysis if no small clusters or microaggregates were present in the 1-hour image, the data are presented on a per-imaging-field basis rather than a per-mouse basis. Data are shown as mean ± SEM; *P < 0.05 by ANOVA with post hoc Tukey testing. Scale bar: 50 μm.