Staphylococcus epidermidis Esp inhibits Staphylococcus aureus biofilm formation and nasal colonization

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Commensal bacteria are known to inhibit pathogen colonization; however, complex host–microbe and microbe–microbe interactions have made it difficult to gain a detailed understanding of the mechanisms involved in the inhibition of colonization1. Here we show that the serine protease Esp2, 3 secreted by a subset of Staphylococcus epidermidis, a commensal bacterium, inhibits biofilm formation and nasal colonization by Staphylococcus aureus, a human pathogen4. Epidemiological studies have demonstrated that the presence of Esp-secreting S. epidermidis in the nasal cavities of human volunteers correlates with the absence of S. aureus. Purified Esp inhibits biofilm formation and destroys pre-existing S. aureus biofilms. Furthermore, Esp enhances the susceptibility of S. aureus in biofilms to immune system components. In vivo studies have shown that Esp-secreting S. epidermidis eliminates S. aureus nasal colonization. These findings indicate that Esp hinders S. aureus colonization in vivo through a novel mechanism of bacterial interference, which could lead to the development of novel therapeutics to prevent S. aureus colonization and infection.

At a glance


  1. Inhibition of S. aureus biofilm formation and destruction of S. aureus biofilms by S. epidermidis.
    Figure 1: Inhibition of S. aureus biofilm formation and destruction of S. aureus biofilms by S. epidermidis.

    a, b, The inhibitory effect of S. epidermidis culture supernatants (a) or cells (b) on S. aureus biofilm formation. c, The destructive effect of S. epidermidis culture supernatants on S. aureus biofilms. After these treatments by S. epidermidis culture supernatants or cells on S. aureus, the amount of S. aureus biofilms was measured. Filled bars, effect of inhibitory S. epidermidis (JK16 strain); open bars, effect of non-inhibitory S. epidermidis (JK11 strain). Bars show the mean value of the experiments (n = 3). Error bars show standard deviation (s.d.).

  2. Isolation and characterization of the serine protease Esp, the factor responsible for the biofilm-destruction activity, secreted by inhibitory S. epidermidis.
    Figure 2: Isolation and characterization of the serine protease Esp, the factor responsible for the biofilm-destruction activity, secreted by inhibitory S. epidermidis.

    a, Growth curve (open circles) of inhibitory S. epidermidis (JK16 strain) and the biofilm-destruction activity (closed circles) of the culture supernatants of the same strain. The activity of the supernatants at 8h is shown as 100%. b, A protein having the biofilm-destruction activity was purified from the culture media of inhibitory S. epidermidis (arrow). M, molecular mass markers. c, Effects of the culture supernatants of inhibitory S. epidermidis (JK16, wild-type strain), an isogenic esp-deficient strain and a complemented strain on S. aureus biofilms. d, The biofilm-destruction activity of purified Esp was blocked by APMSF. (+) or (-) indicate the presence or absence of Esp and APMSF. e, Esp inhibited S. aureus biofilm formation in a dose-dependent manner. f, Esp destroyed S. aureus biofilms in a time-dependent manner. The biofilms were incubated in the presence (closed circles) or absence (open circles) of Esp for the indicated times. g–l, Microscopic observation of S. aureus biofilms incubated for 6h in the presence (j–l) or absence (gi) of Esp. Gram staining (g and j) and scanning electron micrographs (h, i, k, and l) of the biofilms with scale bars (10μm in g, h, j, and k, and 1μm in i and l). The arrows in j indicate the intercellular matrix. m, Esp enhanced the susceptibility of S. aureus in biofilms to hBD2. Viability of S. aureus cells in biofilms, which was incubated in the presence (+ or triangles) or absence (-) of Esp (1μM) and hBD2 (1, 5 and 10μM, from left to right in each triangle) for 6h. The cell viability without Esp and hBD2 was set as 100%. Plots and columns show mean and s.d. (n = 3). Statistical significance is indicated as *P<0.05 and **P<0.01.

  3. Elimination effect of inhibitory S. epidermidis cells on S. aureus nasal colonization.
    Figure 3: Elimination effect of inhibitory S. epidermidis cells on S. aureus nasal colonization.

    a, Representative culture images of samples from test persons after administration of inhibitory S. epidermidis (JK16, wild-type strain). The nasal swabs from the volunteers were cultured on mannitol salt agar with egg yolk. b, The bacterial counts of S. aureus from the nasal swabs after the administration of S. epidermidis cells. JK16 strain (closed circles; n = 7) or an isogenic esp-deficient strain (open circles; n = 6) were placed into the nasal cavities of the volunteers. Plots show mean and s.d. Statistical significance is indicated at *P<0.05. NS, not significant; DL, detection limit. c, Carrier rate of S. aureus after the administration of S. epidermidis wild type cells (closed circles; n = 7) and esp-deficient cells (open circles; n = 6). Statistical significance according to Kaplan–Meier method and log-rank test is at *P<0.05.


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  1. Department of Bacteriology, The Jikei University School of Medicine, Tokyo, 105-8461 Japan

    • Tadayuki Iwase,
    • Hitomi Shinji,
    • Akiko Tajima &
    • Yoshimitsu Mizunoe
  2. Department of General Medicine, Kochi Medical School, Nankoku, 783-8505 Japan

    • Yoshio Uehara &
    • Hiromi Seo
  3. Department of Biochemistry, The Jikei University School of Medicine, Tokyo, 105-8461 Japan

    • Koji Takada
  4. Department of Environmental Health, The Jikei University School of Medicine, Tokyo, 105-8461 Japan

    • Toshihiko Agata


T.I. and Y.M. designed the research and wrote the manuscript. All authors contributed the experiments; T.I., H.S., A.T., K.T. and Y.M. for in vitro study and epidemiological study, Y.U. and H.S. for in vivo study, T.A. for statistics. All authors discussed the results and commented on the manuscript.

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