Also, Staphylococcus aureus ATTC strain 29213 was incubated with anti-granulocyte CD66b antibody. S. aureus was partially detectable in the same region of MPs ( Figure 1C ) but like P. aeruginosa did not show any positivity for the antibody directed against CD66b ( Figure  1F ). Therefore, we conclude that the staining of sputum supernatant was given only by MPs. Figure 2 shows electron microscope picture of sputum-MPs from CF patients. Multiple spherical particles ranging in diameter from 100 to 500 nm were detected. Of note, no bacterial bodies were found associated with MPs.