Fig. 4.

Morphology and quantity and durability of sphingosine/phytosphingosine coatings. 1 cm segments of endotracheal tubes were dip-coated once in a, c, e 30 mM sphingosine or b, d, f 30 mM phytosphingosine in 100% ethanol heated to 70 °C. Segments were then stained with 0.1% osmium tetroxide, sputter-coated with gold/platinum, and imaged with scanning electron microscopy. Images were obtained at different magnifications as indicated. Shown are representative figures from three independent studies. g Left panel: Endotracheal tube segments were dip coated in 30 mM sphingosine solution. Sphingosine was extracted and analyzed by mass spectrometry or measured by a sphingosine kinase assay on the tube. The sphingosine-coated endotracheal tube segments were also immersed in saliva or blood and incubated at 37 °C for 7 days prior to the sphingosine kinase assay. Right panel: Incubation of tube segments after the 7 day incubation in saliva with P. aeruginosa, A. baumannii, or S. aureus still kills the bacteria to a similar degree as without incubation of the coated tube with saliva. Experiments were performed as described in Fig. 1. Shown is the mean ± SD of the sphingosine concentration, n = 3 each or n = 6 for all infection experiments