Limits...
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.

Show MeSH

Related in: MedlinePlus

Macrophages stimulated with interferon-γ kill engulfed S. aureus strains: Newman (A), ATCC 25923 (B), and COL (C) more efficiently than non-stimulated cells.Cells were stimulated with recombinant human IFNγ overnight at concentrations equivalent to human therapeutic doses (100 U ml−1), and then allowed to phagocytose three different strains of S. aureus for 2 h. Infected cultures were processed as described in the legend for Fig. 3A and live bacteria in the whole cultures (CFU) were enumerated up to 14 days postphagocytosis. Since at the longer timepoints no bacterial growth was detected (CFU = 0) these points were not presented on the graph. The data shown is representative of at least three separate experiments, performed in triplicate, using hMDM derived from different donors. Bars represent mean CFU value ±SD. *, p<0.05; **, p<0.01; ***, p<0.001. NS-not significant.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2169301&req=5

pone-0001409-g004: Macrophages stimulated with interferon-γ kill engulfed S. aureus strains: Newman (A), ATCC 25923 (B), and COL (C) more efficiently than non-stimulated cells.Cells were stimulated with recombinant human IFNγ overnight at concentrations equivalent to human therapeutic doses (100 U ml−1), and then allowed to phagocytose three different strains of S. aureus for 2 h. Infected cultures were processed as described in the legend for Fig. 3A and live bacteria in the whole cultures (CFU) were enumerated up to 14 days postphagocytosis. Since at the longer timepoints no bacterial growth was detected (CFU = 0) these points were not presented on the graph. The data shown is representative of at least three separate experiments, performed in triplicate, using hMDM derived from different donors. Bars represent mean CFU value ±SD. *, p<0.05; **, p<0.01; ***, p<0.001. NS-not significant.

Mentions: Interferon-γ (IFNγ) plays an essential role in stimulating cells to eliminate intracellular pathogens [57]. Therefore we checked the effect of IFNγ on the course of hMDMs infection with three different S. aureus strains. As can be clearly seen in Fig. 4, from day 2 onwards there are significant differences between the CFU from the lysates of IFNγ-pretreated or non-treated macrophages. The most dramatic difference was observed on day 6 for Newman (Fig. 4A) and day 5 for strains ATCC 25923 and COL (Fig. 4BC). While S. aureus escaped from non-treated cells into the media, where proliferated explosively, IFNγ-stimulated cells curtailed the numbers of intracellular staphylococci, eliminating strain Newman on day 7, and strains ATCC 25923 or COL on day 6; yielding cultures that were sterile for up to 6 consecutive days (end of experiment) after the intracellular infection was cleared. These results demonstrate that as in the case of other intracellular pathogens [57], the infection of hMDMs by S. aureus can be resolved if macrophages are primed with IFNγ.


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)

Macrophages stimulated with interferon-γ kill engulfed S. aureus strains: Newman (A), ATCC 25923 (B), and COL (C) more efficiently than non-stimulated cells.Cells were stimulated with recombinant human IFNγ overnight at concentrations equivalent to human therapeutic doses (100 U ml−1), and then allowed to phagocytose three different strains of S. aureus for 2 h. Infected cultures were processed as described in the legend for Fig. 3A and live bacteria in the whole cultures (CFU) were enumerated up to 14 days postphagocytosis. Since at the longer timepoints no bacterial growth was detected (CFU = 0) these points were not presented on the graph. The data shown is representative of at least three separate experiments, performed in triplicate, using hMDM derived from different donors. Bars represent mean CFU value ±SD. *, p<0.05; **, p<0.01; ***, p<0.001. NS-not significant.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0001409-g004: Macrophages stimulated with interferon-γ kill engulfed S. aureus strains: Newman (A), ATCC 25923 (B), and COL (C) more efficiently than non-stimulated cells.Cells were stimulated with recombinant human IFNγ overnight at concentrations equivalent to human therapeutic doses (100 U ml−1), and then allowed to phagocytose three different strains of S. aureus for 2 h. Infected cultures were processed as described in the legend for Fig. 3A and live bacteria in the whole cultures (CFU) were enumerated up to 14 days postphagocytosis. Since at the longer timepoints no bacterial growth was detected (CFU = 0) these points were not presented on the graph. The data shown is representative of at least three separate experiments, performed in triplicate, using hMDM derived from different donors. Bars represent mean CFU value ±SD. *, p<0.05; **, p<0.01; ***, p<0.001. NS-not significant.
Mentions: Interferon-γ (IFNγ) plays an essential role in stimulating cells to eliminate intracellular pathogens [57]. Therefore we checked the effect of IFNγ on the course of hMDMs infection with three different S. aureus strains. As can be clearly seen in Fig. 4, from day 2 onwards there are significant differences between the CFU from the lysates of IFNγ-pretreated or non-treated macrophages. The most dramatic difference was observed on day 6 for Newman (Fig. 4A) and day 5 for strains ATCC 25923 and COL (Fig. 4BC). While S. aureus escaped from non-treated cells into the media, where proliferated explosively, IFNγ-stimulated cells curtailed the numbers of intracellular staphylococci, eliminating strain Newman on day 7, and strains ATCC 25923 or COL on day 6; yielding cultures that were sterile for up to 6 consecutive days (end of experiment) after the intracellular infection was cleared. These results demonstrate that as in the case of other intracellular pathogens [57], the infection of hMDMs by S. aureus can be resolved if macrophages are primed with IFNγ.

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