MRSA replicate inside phagolysosomes of KCs. (a) SD-IVM image of mouse livers injected with pH-rodo S. aureus bioparticles (red) additionally labeled with AF647 (blue) as reference fluorophore, showing no acidification at 8 m. Almost all bioparticles were acidified (as indicated by the shift to red staining) at 30 m after infection (Video 4). Bar, 50 µm. (b) Quantification of intracellular acidification of pH-rodo S. aureus bioparticles in KCs over time. Data represent percentage of acidified S. aureus bioparticles compiled from five separate FOV per time point. n = 4 mice. Error bars, SEM. (c) Immunofluorescence image of intracellular localization of replicating Staphylococci. Green, MRSA (MW2-GFP) co-localizes with LAMP-1 (blue) inside KCs (F4/80, purple). Bars, 5 µm. (d) Quantification of co-localization of MRSA with LAMP-1 in KCs at 30 m and 8 h after infection. Data represent percentage of 50 analyzed KCs per mice. n = 3. Error bars, SEM; Student’s t test. (e) Electron microscopy image of dividing intracellular MRSA (MW2) at 8 h after infection. EC, endothelial cell; SA, S. aureus. Bar, 2.5 µm. Shown is one representative image out of three independent experiments.