Impact of 20-kDaPS antiserum on endocytosis of S. epidermidis by human macrophages. Bacterial suspensions of 20-kDaPS-producing S. epidermidis reference strain ATCC35983 and non-20-kDaPS producing S. epidermidis clinical strain 1505 preincubated with PBS (ctl), preimmune serum (preI), and 20-kDaPS antiserum (I) were added to human macrophages. The number of endocytosed bacteria was counted by serial dilutions of cell lysates on blood agar. Columns represent mean values of endocytosed bacteria from a representative experiment out of five similar ones performed in triplicate. (*) p < 0.05, (**) p < 0.005, (NS) p > 0.05.