Staphylococcus epidermidis Esp inhibits Staphylococcus aureus biofilm formation and nasal colonization

Tadayuki lwase, et al. Nature 465: 346–349 (2010)

Speaker: Shu-Chun Chien (簡淑珺)                              Time: 15:10~16:00, Sep. 29, 2010

Commentator: Dr. Ching-Hao Teng (鄧景浩老師)      Place: Room 601

Abstract:

It has been known that the commensal bacteria can protect the host from being invaded by the pathogens, but the interactions between microbes or host and microbe are still unclear. In this study, the authors demonstrated that the serine protease, Esp, secreted by Staphylococcus epidermis, a dominant commensal bacterial species inhabiting the human nasal cavity, could inhibite the biofilm formation and nasal colonization of Staphylococcus aureus. They first analyzed the S. epidermis isolates from the nasal cavities of 88 volunteers and found that they could be divided into two types: one can inhibit S. aureus (inhibitory type) while the other cannot (non-inhibitory type). They then found that the inhibitory S. epidermis could destroy the pre-existing S. aureus biofilms. Through a series of fractionation procedures with the culture supernatant, they identified the inhibitory factor of S. epidermidis as a serine protease, designated Esp. A S. epidermidis mutant deficient in Esp lost the S. aureus biofilm destruction activity. The Esp protein destroyed the intracellular matrix of a S. aureus biofilm in a dose- and time-dependent manner. Moreover, the treatment of Esp with a serine-protease inhibitor, amidinophyl methansulphonyl fluoride, completely blocked the biofilm destruction ability of this enzyme. Collectively, these data indicated that some S. epidermidis strains can secret Esp to destroy the biofilm of S. aureus. They then showed that in combination with Esp, the human antimicrobial peptide, β-defensin (hBD2), could effectively kill S. aureus in the biofilm. In an in vivo study, they further showed that the introduction of Esp-secreting S. epidermidis into the nasal cavities of the S. aureus carriers could rapidly eliminate S. aureus colonization. These results suggest that Esp may be used as a novel therapy to prevent S. aureus colonization and infection.

References

1.      Kluytmans, J., et al. Nasal carriage of Staphylococcus aureus: epidemiology, underlying, mechanisms, and associated risks. Clin. Microbiol. Rev. 10, 505-520 (1997)

2.      Falagas, M. E., et al. Bacterial interference for the prevention and treatment of infections. Int. J. Antimicrob. Agents 31, 518-522 (2008).