Pediatric Research (2009) 66, 174–178; doi:10.1203/PDR.0b013e3181a9d80c

Staphylococcus epidermidis Isolated From Newborn Infants Express Pilus-Like Structures and Are Inhibited by the Cathelicidin-Derived Antimicrobial Peptide LL37

Annika Nelson1, Kjell Hultenby4, Éva Hell1, Hilde M Riedel2, Hjalmar Brismar5, Jan-Ingmar Flock2, Joachim Lundahl3, Christian G Giske2 and Giovanna Marchini1

  1. 1Departments of Woman and Child Health, Karolinska Institutet, Stockholm 17176, Sweden
  2. 2Departments of Clinical Microbiology, Karolinska Institutet, Stockholm 17176, Sweden
  3. 3Departments of Medicine, Karolinska Institutet, Stockholm 17176, Sweden
  4. 4Department of Laboratory Medicine, Karolinska Institutet, Stockholm 14186, Sweden
  5. 5Department of Cell Physics, Royal Institute of Technology, Stockholm 10691, Sweden

Correspondence: Giovanna Marchini, M.D. Ph.D., Neonatal Unit at Astrid Lindgren Children's Hospital, FRH-lab, C4:U1, Karolinska University Hospital Solna, 17176 Stockholm, Sweden; e-mail:

Received 5 February 2009; Accepted 25 March 2009

Supported by Frimurarbarnhuset Stockholm, Sällskapet Barnavård, Stiftelsen Samariten, and Crown Princess Lovisa Memory Foundation.



Coagulase-negative staphylococci and its subtype Staphylococcus epidermidis are major indigenous Gram-positive inhabitants of the human skin. Colonization occurs in direct connection with birth and terrestrial adaptation. This study focuses on factors that may influence skin colonization of the newborn infant that relates to the immune status of both the bacteria and the host. Skin is an effective barrier against bacteria, and this function is partly mediated by the presence of antimicrobial peptides including human cathelicidin peptide LL37. Gram-positive bacteria have been described to have adhesive pili on their surface that mediates specific attachment to the host. Here, we identify, by negative staining transmission electron microscopy (EM), two different types of pilus-like structures commonly expressed on S. epidermidis isolated from newborn infants. We also show that the cathelicidin antimicrobial peptide LL37, constitutively expressed in the skin barrier of the newborn, significantly inhibited growth of S. epidermidis indicating its importance for the ecological stability of the skin microbiota. Further studies are required to elucidate molecular mechanisms of host-microbe interactions, both for the maintenance of a mutually beneficial homeostatic relationship and for the protection of self when it results in overt disease.


Aap, accumulation-associated protein; BHI, brain-heart infusion; CI, clinical isolate; CoNS, coagulase-negative staphylococci; EM, electron microscopy; Fbe, fibrinogen-binding protein; MHB, Mueller Hinton broth; MIC, minimal inhibitory concentration