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A potential new pathway for Staphylococcus aureus dissemination: the silent survival of S. aureus phagocytosed by human monocyte-derived macrophages.

Kubica M, Guzik K, Koziel J, Zarebski M, Richter W, Gajkowska B, Golda A, Maciag-Gudowska A, Brix K, Shaw L, Foster T, Potempa J - PLoS ONE (2008)

Bottom Line: In particular alpha-toxin was a key effector molecule that was essential for S. aureus intracellular survival in macrophages.Together, our data indicate that the ability of S. aureus to survive phagocytosis by macrophages is determined by multiple virulence factors in a way that differs considerably from its interactions with other cell types.S. aureus persists inside macrophages for several days without affecting the viability of these mobile cells which may serve as vehicles for the dissemination of infection.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland. staphaureus@gmail.com

ABSTRACT
Although considered to be an extracellular pathogen, Staphylococcus aureus is able to invade a variety of mammalian, non-professional phagocytes and can also survive engulfment by professional phagocytes such as neutrophils and monocytes. In both of these cell types S. aureus promptly escapes from the endosomes/phagosomes and proliferates within the cytoplasm, which quickly leads to host cell death. In this report we show that S. aureus interacted with human monocyte-derived macrophages in a very different way to those of other mammalian cells. Upon phagocytosis by macrophages, S. aureus persisted intracellularly in vacuoles for 3-4 days before escaping into the cytoplasm and causing host cell lysis. Until the point of host cell lysis the infected macrophages showed no signs of apoptosis or necrosis and were functional. They were able to eliminate intracellular staphylococci if prestimulated with interferon-gamma at concentrations equivalent to human therapeutic doses. S. aureus survival was dependent on the alternative sigma factor B as well as the global regulator agr, but not SarA. Furthermore, isogenic mutants deficient in alpha-toxin, the metalloprotease aureolysin, protein A, and sortase A were efficiently killed by macrophages upon phagocytosis, although with different kinetics. In particular alpha-toxin was a key effector molecule that was essential for S. aureus intracellular survival in macrophages. Together, our data indicate that the ability of S. aureus to survive phagocytosis by macrophages is determined by multiple virulence factors in a way that differs considerably from its interactions with other cell types. S. aureus persists inside macrophages for several days without affecting the viability of these mobile cells which may serve as vehicles for the dissemination of infection.

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Related in: MedlinePlus

S. aureus infected macrophages retained their bactericidal functions.Control hMDMs, and cells 4 days post infection with S. aureus strain Newman, were stimulated to phagocytose either live bacteria at a MOI of 1∶25 (1.25×107 CFU) (panel A) or latex beads (panel B). Generation of reactive oxygen species (ROS) determined as the level of the mean fluorescence intensity (MFI) was measured at various time intervals. The data shown is representative of at least three separate experiments, performed in triplicate, using hMDMs derived from different donors.
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pone-0001409-g002: S. aureus infected macrophages retained their bactericidal functions.Control hMDMs, and cells 4 days post infection with S. aureus strain Newman, were stimulated to phagocytose either live bacteria at a MOI of 1∶25 (1.25×107 CFU) (panel A) or latex beads (panel B). Generation of reactive oxygen species (ROS) determined as the level of the mean fluorescence intensity (MFI) was measured at various time intervals. The data shown is representative of at least three separate experiments, performed in triplicate, using hMDMs derived from different donors.

Mentions: That the metabolic activity of the infected macrophages was maintained suggested that the bactericidal functions of these cells was also undisturbed. In order to verify this assertion we compared the respiratory burst response of control and infected hMDMs after the phagocytosis of latex beads and live bacteria. As shown in Fig. 2 the kinetics of increased mean fluorescence intensity (MFI), which is a measure of the production of reactive oxygen species (ROS) by cells, was very similar during phagocytosis of both live bacteria (Fig. 2A) and latex beads (Fig. 2B). However, at each time interval the infected hMDMs produced at least twice as much ROS as control cells that took up latex beads or live bacterial cells. Thus, it is clear that infection with S. aureus not only does not suppress antibacterial activity of macrophages, but on the contrary, infected cells were primed for a very vigorous response to phagocytic stimuli.


A potential new pathway for Staphylococcus aureus dissemination: the silent survival of S. aureus phagocytosed by human monocyte-derived macrophages.

Kubica M, Guzik K, Koziel J, Zarebski M, Richter W, Gajkowska B, Golda A, Maciag-Gudowska A, Brix K, Shaw L, Foster T, Potempa J - PLoS ONE (2008)

S. aureus infected macrophages retained their bactericidal functions.Control hMDMs, and cells 4 days post infection with S. aureus strain Newman, were stimulated to phagocytose either live bacteria at a MOI of 1∶25 (1.25×107 CFU) (panel A) or latex beads (panel B). Generation of reactive oxygen species (ROS) determined as the level of the mean fluorescence intensity (MFI) was measured at various time intervals. The data shown is representative of at least three separate experiments, performed in triplicate, using hMDMs derived from different donors.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2169301&req=5

pone-0001409-g002: S. aureus infected macrophages retained their bactericidal functions.Control hMDMs, and cells 4 days post infection with S. aureus strain Newman, were stimulated to phagocytose either live bacteria at a MOI of 1∶25 (1.25×107 CFU) (panel A) or latex beads (panel B). Generation of reactive oxygen species (ROS) determined as the level of the mean fluorescence intensity (MFI) was measured at various time intervals. The data shown is representative of at least three separate experiments, performed in triplicate, using hMDMs derived from different donors.
Mentions: That the metabolic activity of the infected macrophages was maintained suggested that the bactericidal functions of these cells was also undisturbed. In order to verify this assertion we compared the respiratory burst response of control and infected hMDMs after the phagocytosis of latex beads and live bacteria. As shown in Fig. 2 the kinetics of increased mean fluorescence intensity (MFI), which is a measure of the production of reactive oxygen species (ROS) by cells, was very similar during phagocytosis of both live bacteria (Fig. 2A) and latex beads (Fig. 2B). However, at each time interval the infected hMDMs produced at least twice as much ROS as control cells that took up latex beads or live bacterial cells. Thus, it is clear that infection with S. aureus not only does not suppress antibacterial activity of macrophages, but on the contrary, infected cells were primed for a very vigorous response to phagocytic stimuli.

Bottom Line: In particular alpha-toxin was a key effector molecule that was essential for S. aureus intracellular survival in macrophages.Together, our data indicate that the ability of S. aureus to survive phagocytosis by macrophages is determined by multiple virulence factors in a way that differs considerably from its interactions with other cell types.S. aureus persists inside macrophages for several days without affecting the viability of these mobile cells which may serve as vehicles for the dissemination of infection.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland. staphaureus@gmail.com

ABSTRACT
Although considered to be an extracellular pathogen, Staphylococcus aureus is able to invade a variety of mammalian, non-professional phagocytes and can also survive engulfment by professional phagocytes such as neutrophils and monocytes. In both of these cell types S. aureus promptly escapes from the endosomes/phagosomes and proliferates within the cytoplasm, which quickly leads to host cell death. In this report we show that S. aureus interacted with human monocyte-derived macrophages in a very different way to those of other mammalian cells. Upon phagocytosis by macrophages, S. aureus persisted intracellularly in vacuoles for 3-4 days before escaping into the cytoplasm and causing host cell lysis. Until the point of host cell lysis the infected macrophages showed no signs of apoptosis or necrosis and were functional. They were able to eliminate intracellular staphylococci if prestimulated with interferon-gamma at concentrations equivalent to human therapeutic doses. S. aureus survival was dependent on the alternative sigma factor B as well as the global regulator agr, but not SarA. Furthermore, isogenic mutants deficient in alpha-toxin, the metalloprotease aureolysin, protein A, and sortase A were efficiently killed by macrophages upon phagocytosis, although with different kinetics. In particular alpha-toxin was a key effector molecule that was essential for S. aureus intracellular survival in macrophages. Together, our data indicate that the ability of S. aureus to survive phagocytosis by macrophages is determined by multiple virulence factors in a way that differs considerably from its interactions with other cell types. S. aureus persists inside macrophages for several days without affecting the viability of these mobile cells which may serve as vehicles for the dissemination of infection.

Show MeSH
Related in: MedlinePlus