Phagolysosomal Integrity Is Generally Maintained afterStaphylococcus aureusInvasion of Nonprofessional Phagocytes but Is Modulated by Strain 6850

• DOI: 10.1128/iai.00012-10
• Publication Date: 2010-06-08T00:34:47Z
• Authors: Thiên-Trí Lâm; Bernd Giese; Deepak Chikkaballi; Anika Kühn; Wanja Wolber; Jan Pané-Farré; Daniel Schäfer; Susanne Engelmann; Martin Fraunholz; Bhanu Sinha
• Keywords: 0301 basic medicine; Phagocytes; Staphylococcus aureus; 03 medical and health sciences; Microscopy, Electron, Transmission; Phagosomes; Humans; Epithelial Cells; Intracellular Membranes; Hydrogen-Ion Concentration; Cell Line; 3. Good health

ABSTRACTStaphylococcus aureusis a major cause of a variety of both local and systemic infections. It can invade human host cells, a process that may account for disseminated and recurrent infections.S. aureuspostinvasion events in nonprofessional phagocytes are only partially understood. While morphological data suggest a phagosomal escape, there is a lack of corroborating functional data. Using a combination of pH determination and morphological techniques, we have tested the integrity ofStaphylococcus-containing phagosomes in 293 (HEK-293), HeLa, and EA.hy926 cells over time. Rapid acidification ofS. aureus-containing phagosomes occurred and was sustained for up to 24 h. AllS. aureusstrains tested displayed equally sustained intraphagosomal pH levels without exhibiting any correlation with pH level and hemolytic activity. The membrane morphology of the phagosomal compartment was heterogeneous, even under conditions where acidic pH was fully maintained, an observation incompatible with phagolysosomal membrane destruction. As an exception,S. aureusstrain 6850 showed a reduced phagosomal acidification signal 6 h after invasion. Additionally, only strain 6850 failed to localize to LAMP-1-positive vesicles in HeLa cells, although this was observed only rarely. Several other strongly beta-hemolytic strains did not modulate phagolysosomal pH, suggesting thatS. aureusα-toxin and β-toxin are not sufficient for this process. Taken together, our data suggest thatS. aureus-containing phagolysosomes generally remain functionally intact in nonprofessional phagocytes, thereby contrasting with transmission electron micrographic results.