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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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Functional sigB and agr operons, but not sarA, are indispensable for S. aureus to survive phagocytosis by hMDMs.Macrophages were allowed to engulf defined strains of S. aureus for 2h at a MOI of 25, and the intracellular survival of bacteria on consecutive days post-phagocytosis was monitored by enumeration of the CFU of cell lysates (see Fig. 3A legend). The data shown is representative of at least three separate experiments, performed in triplicate, using hMDMs derived from different donors. Bars represent mean CFU value ±SD. A. 8325-4, a natural rsbU defective strain lacking a functional SigB. B. SH1000, a derivative of strain 8325-4 with a restored rsbU gene and SigB activity. C. Newman sigB mutant D. Newman agr mutant E. Newman sarA mutant F. Newman wild-type
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pone-0001409-g006: Functional sigB and agr operons, but not sarA, are indispensable for S. aureus to survive phagocytosis by hMDMs.Macrophages were allowed to engulf defined strains of S. aureus for 2h at a MOI of 25, and the intracellular survival of bacteria on consecutive days post-phagocytosis was monitored by enumeration of the CFU of cell lysates (see Fig. 3A legend). The data shown is representative of at least three separate experiments, performed in triplicate, using hMDMs derived from different donors. Bars represent mean CFU value ±SD. A. 8325-4, a natural rsbU defective strain lacking a functional SigB. B. SH1000, a derivative of strain 8325-4 with a restored rsbU gene and SigB activity. C. Newman sigB mutant D. Newman agr mutant E. Newman sarA mutant F. Newman wild-type

Mentions: The intracellular survival of S. aureus in neutrophils, as well as in non-professional phagocytes, depends on multiple virulence factors, including global regulators of gene expression [32], [40]. Therefore we compared the uptake and intracellular killing/survival of S. aureus strains deficient in agr, sarA or sigB. First we examined the survival of S. aureus strain 8325-4 in which an 11bp deletion in the rsbU gene renders the sigB operon essentially non-functional [60]. Macrophages cleared intracellular 8325-4 within two days, apparently by killing the bacteria in phagolysosome (Fig. 6A). The importance of sigB was confirmed by the finding that S. aureus strain SH1000, 8325-4 with a restored rsbU gene and a functional sigB operon [61], survived phagocytosis (Fig. 6B). Furthermore, a Newman sigB mutant was unable to survive phagocytosis, with all ingested bacteria killed within 2 days (Fig. 6C).


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)

Functional sigB and agr operons, but not sarA, are indispensable for S. aureus to survive phagocytosis by hMDMs.Macrophages were allowed to engulf defined strains of S. aureus for 2h at a MOI of 25, and the intracellular survival of bacteria on consecutive days post-phagocytosis was monitored by enumeration of the CFU of cell lysates (see Fig. 3A legend). The data shown is representative of at least three separate experiments, performed in triplicate, using hMDMs derived from different donors. Bars represent mean CFU value ±SD. A. 8325-4, a natural rsbU defective strain lacking a functional SigB. B. SH1000, a derivative of strain 8325-4 with a restored rsbU gene and SigB activity. C. Newman sigB mutant D. Newman agr mutant E. Newman sarA mutant F. Newman wild-type
© Copyright Policy
Related In: Results  -  Collection

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

pone-0001409-g006: Functional sigB and agr operons, but not sarA, are indispensable for S. aureus to survive phagocytosis by hMDMs.Macrophages were allowed to engulf defined strains of S. aureus for 2h at a MOI of 25, and the intracellular survival of bacteria on consecutive days post-phagocytosis was monitored by enumeration of the CFU of cell lysates (see Fig. 3A legend). The data shown is representative of at least three separate experiments, performed in triplicate, using hMDMs derived from different donors. Bars represent mean CFU value ±SD. A. 8325-4, a natural rsbU defective strain lacking a functional SigB. B. SH1000, a derivative of strain 8325-4 with a restored rsbU gene and SigB activity. C. Newman sigB mutant D. Newman agr mutant E. Newman sarA mutant F. Newman wild-type
Mentions: The intracellular survival of S. aureus in neutrophils, as well as in non-professional phagocytes, depends on multiple virulence factors, including global regulators of gene expression [32], [40]. Therefore we compared the uptake and intracellular killing/survival of S. aureus strains deficient in agr, sarA or sigB. First we examined the survival of S. aureus strain 8325-4 in which an 11bp deletion in the rsbU gene renders the sigB operon essentially non-functional [60]. Macrophages cleared intracellular 8325-4 within two days, apparently by killing the bacteria in phagolysosome (Fig. 6A). The importance of sigB was confirmed by the finding that S. aureus strain SH1000, 8325-4 with a restored rsbU gene and a functional sigB operon [61], survived phagocytosis (Fig. 6B). Furthermore, a Newman sigB mutant was unable to survive phagocytosis, with all ingested bacteria killed within 2 days (Fig. 6C).

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