Affiliation:
1. Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital,1 and
2. Department of Medicine, Children’s Hospital,2 Harvard Medical School, Boston, Massachusetts 02115-5899
Abstract
ABSTRACT
Clinical isolates of coagulase-negative staphylococci often elaborate a biofilm involved in adherence to medical devices and resistance to host defenses. The biofilm contains the capsular polysaccharide/adhesin (PS/A), which mediates cell adherence to biomaterials, and another antigen, termed polysaccharide intercellular adhesin (PIA), which is thought to mediate bacterial accumulation into cellular aggregates. PIA is a polymer of β-1,6-linked
N
-acetyl glucosamine residues with a molecular mass of <30,000 kDa. We found that recombinant
Staphylococcus carnosus
and
Staphylococcus aureus
carrying a plasmid with genes of the
ica
locus, which was reported to encode the biosynthetic proteins for production of PIA, were also able to synthesize PS/A. PS/A and a chemically and immunologically identical polysaccharide isolated from
S. carnosus
carrying the
ica
genes on plasmid pCN27 were found to be high-molecular-mass (>250,000 kDa), acid-stable polymers of β-1,6-linked glucosamine substituted on the amino group primarily with succinate, although some preparations also contained acetate. Moreover, all recombinant staphylococcal strains with the
ica
genes had the biologic properties previously attributed to PS/A.
ica
-positive strains readily formed an in vitro biofilm on plastic, adhered 3- to 10-fold more to catheters during a 30-min assay compared with control strains carrying only the cloning vector, adsorbed out antibodies to PS/A from immune serum, and elaborated a capsule visualized by immunoelectron microscopy with antisera to PS/A. These properties were also seen with PS/A-producing strains of
Staphylococcus epidermidis
, but not with transposon mutants lacking PS/A. An antiserum raised to PIA contained high-titer antibody to PS/A that was readily adsorbed out by PS/A-positive strains of
S. epidermidis
and recombinant strains of staphylococci carrying the
ica
genes. We conclude that the
ica
locus encodes production of PS/A and that the properties of
S. epidermidis
associated with initial bacterial adherence, biofilm formation, and intercellular adhesion can be correlated with elaboration of PS/A.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
268 articles.
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