Fibronectin and fibrinogen contribute to the enhanced binding of Staphylococcus aureus to atopic skin.
BACKGROUND
Staphylococcus aureus colonizes the skin lesions of more than 90% of patients with atopic dermatitis (AD). The mechanism for increased S aureus colonization in AD is unknown. However, the initial event in colonization requires adherence of S aureus to the skin.


OBJECTIVE
The purpose of this study was to examine the roles of various bacterial adhesins on S aureus binding to AD skin.


METHODS
In an attempt to delineate the mechanism behind this adherence process, an in vitro bacterial binding assay was developed to quantitate the adherence of various S aureus strains to AD, psoriatic, and normal skin sections. S aureus strains used in this study were obtained either from cultures of AD skin lesions or from genetically manipulated strains of S aureus that lacked specific microbial surface components recognizing adhesive matrix molecules (MSCRAMMs)--namely, fibronectin-binding protein (Fnbp), fibrinogen-binding protein (Clf), collagen-binding protein (Cna), and their parent strains. In addition, S aureus strains from patients with AD were pretreated with fibronectin or fibrinogen to block MSCRAMM receptors and interfere with binding.


RESULTS
Under all experimental conditions, binding of S aureus was localized primarily to the stratum corneum. Immunocytochemical staining of AD skin sections showed a redistribution of fibronectin to the cornified layer, an observation not seen in normal skin. S aureus binding to uninvolved AD skin was significantly greater than the binding to uninvolved psoriatic skin (P <.0001) and normal skin (P <.0005). The Fnbp-negative S aureus showed a significant reduction in binding to the AD skin (P <.0001) but not to the psoriatic and normal skin. In the AD skin, a significant reduction in the binding of S aureus was also observed in the Clf-negative strain (P <.0001) but not in the Cna-negative S aureus. Preincubation of S aureus with either fibronectin or fibrinogen also inhibited bacterial binding to AD skin (P <.0001).


CONCLUSIONS
These data suggest that fibronectin and fibrinogen--but not collagen--play a major role in the enhanced binding of S aureus to the skin of patients with AD.
Cho
S H
SH
Department of Pediatrics, National Jewish Medical and Research Center, Denver. CO 80206, USA.
Strickland
I
I
Boguniewicz
M
M
Leung
D Y
DY
D001422:Bacterial Adhesion / Q000502:physiology*; D015815:Cell Adhesion Molecules; D003876:Dermatitis, Atopic / Q000150:complications*; D016326:Extracellular Matrix Proteins; D005340:Fibrinogen / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism*; D006801:Humans; D011565:Psoriasis / Q000150:complications; D013207:Staphylococcal Skin Infections / Q000209:etiology*; D013211:Staphylococcus aureus / Q000235:genetics
D015815:Cell Adhesion Molecules; D016326:Extracellular Matrix Proteins; D005353:Fibronectins; D005340:Fibrinogen