Hydrophobicity-hydrophilicity of staphylococci.

The hydrophobicity-hydrophilicity of various strains of Staphylococcus has been studied by a technique involving partitioning of the cells between aqueous and hydrocarbon phases. S. aureus was typically hydrophobic, and to a greater degree in stationary- than in exponential-phase cultures. Mutants that lacked teichoic acid, protein A or coagulase production were hydrophobic, indicating that none of these factors was responsible for hydrophobicity. The presence of a capsule rendered strains hydrophilic. Thus, determination of hydrophobicity may be a useful additional test for capsulation. However, a non-capsulate S. aureus strain was hydrophilic. Trypsin treatment converted strains from hydrophobic to hydrophilic. Isolated bacterial cell wall preparation, either crude or purified, and peptidoglycan were hydrophilic. These results indicate that the determinant of hydrophobicity is a protein or protein-associated molecule localised at the cell surface of the organism, i.e., a component of either the cell wall, cell membrane, or both. Twenty-five strains of twelve coagulase-negative species were examined and most (18) were hydrophobic, again indicating that protein A is not a major determinant of hydrophobicity in these staphylococci. Four of seven hydrophilic strains were capsulate; three strains of S. sciuri were hydrophilic but non-capsulate.

Protein-mediated adhesion of Staphylococcus aureus to silicone implant polymer.

Investigation was made of the role of protein A and clumping factor in the adhesion of Staphylococcus aureus to the silicone polymer used for manufacture of cerebrospinal fluid shunting systems. The two proteins were judged to contribute non-specifically to adhesion. S. aureus was also shown to be capable of hydrophobic binding, but this was found to be distinct from the demonstrated protein-mediated adhesion.

A non-dissociable rabbit IgG-protein a complex.

Glutaraldehyde treatment of rabbit IgG antibody complexed with protein A of Staphylococcus aureus (SpA) enabled the complex (IgG2-SpA1)2 to maintain its molecular weight unchanged and to become non-dissociable at low pH and in excess of IgG. The glutaraldehyde-treated (IgG2-SpA1)2 complex had the same half-life, complement-activating capacity and ability to interact with the Fc receptor as the non-treated complex. Moreover, the glutaraldehyde-treated complex had a stronger immunosuppressive effect on the synthesis of anti-sheep red blood cell antibody than either the non-complexed antibody or the IgG antibody complexed with SpA but untreated with glutaraldehyde.

Protein A effect on alternative pathway complement activation and opsonization of Staphylococcus aureus.

Twelve Staphylococcus aureus strains with known amounts of protein A were compared with regard to alternative pathway complement activation and opsonization in human serum. "Protein A-poor" strains (less than or equal to 0.16 ng/10(6) bacteria) were, on the average, 3. 4-fold more efficient in alternative pathway complement activation than "protein A-rich" strains (greater than or equal to 0.625 ng/10(6) bacteria) (P less than 0.001). Protein A-poor strains were significantly better phagocytized by human polymorphonuclear leukocytes after opsonization in magnesium-ethylene glycol-bis (beta-amino-ethyl ether)-N, N-tetraacetic acid-chelated serum than were the protein A-rich strains (P less than 0.001). No significant differences between protein A-poor and -rich strains were found in complement activation and opsonization in normal serum. Cell wall-bound protein A appeared to hinder alternative pathway complement activation by S. aureus, which resulted in decreased opsonization of these bacteria in the absence of an intact classical pathway. These studies suggest that protein A may cover alternative pathway complement-activating sites within the peptidoglycan matrix of the staphylococcal cell wall.

Human fibronectin binding to staphylococcal surface protein and its relative inefficiency in promoting phagocytosis by human polymorphonuclear leukocytes, monocytes, and alveolar macrophages.

The interaction between human fibronectin and 17 strains of staphylococci was studied in an attempt to elucidate the staphylococcal cell wall component(s) involved in fibronectin binding and to determine the influence of fibronectin upon phagocytosis by three types of phagocytic cells. Purified, radiolabeled fibronectin bound to a similar degree to six laboratory strains and three fresh clinical isolates of Staphylococcus aureus; similar binding of fibronectin was found with S. aureus strains deficient in cell wall teichoic acid or clumping factor and coagulase, as well as with three strains of S. epidermidis. There was minimal binding of fibronectin to encapsulated S. aureus and to Escherichia coli. Fibronectin bound to intact cells and to a crude cell wall preparation of S. aureus H, but not to purified cell walls or peptidoglycan. Trypsinization of staphylococci prevented subsequent fibronectin binding, but binding did not correlate well with the protein A content in S. aureus cell walls. At physiological concentrations, fibronectin binding to staphylococci did not promote phagocytosis of bacteria by human polymorphonuclear leukocytes, monocytes, or alveolar macrophages. Also, depletion of fibronectin from normal human serum did not result in a measurable loss of opsonic activity for staphylococci. It is concluded that fibronectin binding to staphylococci involves a surface protein shared among strains of S. aureus and S. epidermidis, and that in comparison to C3b and IgG, fibronectin plays a relatively minor role as an opsonin for staphylococci.