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B J Wilkinson

Publications and source records attributed to B J Wilkinson.

At least 73 records · Page 4Linked to original sources
PubMed1981

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.

Bacterial Proteins↗
PubMed1981

Differential methicillin susceptibilities of peptidoglycan syntheses in methicillin-resistant Staphylococcus aureus.

The mechanism of staphylococcal resistance to methicillin is unknown. Peptidoglycan synthesis was studied in a methicillin-resistant and a derived methicillin-sensitive Staphylococcus aureus strain. Although the methicillin minimum inhibitory concentration for growth of the methicillin-resistant strain was 1,600 micrograms/ml, peptidoglycan synthesis by the organism incubated in a wall synthesis solution was inhibited about 90% by 5 micrograms of methicillin per ml. In contrast, high concentrations of methicillin added to actively growing cultures of the methicillin-resistant strain had little effect on growth or peptidoglycan synthesis. Peptidoglycan synthesis in chloramphenicol-treated cultures was more susceptible to methicillin than it was in actively growing cultures of the methicillin-resistant strain. It is proposed that in this strain cell wall thickening peptidoglycan synthesis which predominates in cell wall synthesis solution and chloramphenicol-treated cultures is methicillin sensitive, whereas peptidoglycan synthesis involved in cell division, primarily in the region of the septum, which predominates in actively growing cultures is methicillin resistant. Both cell wall thickening and septal peptidoglycan syntheses are methicillin sensitive in the methicillin-sensitive strain.

Chloramphenicol↗
PubMed1980

Immunoglobulin E antibodies against Staphylococcus aureus cell walls in the sera of patients with hyperimmunoglobulinemia E and recurrent staphylococcal infection.

The specificity of antistaphylococcal antibodies of the IgE class in five patients with hyperimmunoglobulinemia E and recurrent staphylococcal infection has been investigated. Purified cell walls were prepared from various staphylococcal strains, and serum immunoglobulin E binding was measured by using a solid-phase radioimmunoassay. Immunoglobulin E binding occurred only with cell walls from Staphylococcus aureus strains, including walls from a teichoic acid-deficient mutant. Immunoglobulin E did not bind to cell wall preparations from the coagulase-negative species S. capitis, S. sciuri subsp. lentus, S. simulans, S. xylosus, staphylococcal strains RB-11 and Armour, and from a group A streptococcus strain CS44. Since the glycan backbone and the tetrapeptide (pentapeptide) subunit of the peptidoglycan of all staphylococcal strains tested are believed to be identical, it is suggested that IgE binding is related to either the peptidoglycan interpeptide bridge or an unknown antigenic structure within the cell wall of S. aureus. The pathophysiological significance of antistaphylococcal immunoglobulin E antibodies in the disorder studied is at present unknown. The formation of immunoglobulin E antibodies to S. aureus cell wall components may be a manifestation of an aberrant immunological response to S. aureus related to the undue susceptibility to staphylococcal infections in these patients.

Antibodies, Bacterial↗
PubMed1980

Facile penetration of the Staphylococcus aureus capsule by lysostaphin.

The ability of macromolecules to cross the capsular layer of encapsulated microorganisms and interact with their cell walls is important in considerations of the mechanisms of resistance to phagocytosis and of antigen masking in such strains. Lysostaphin was employed as a probe of the penetrability of the Staphylococcus aureus capsule. The rates of lysostaphin-induced lysis of encapsulated and unencapsulated S. aureus strains were compared. Encapsulated S. aureus strains M and Smith diffuse were lysed by lysostaphin at the same rate as their respective unencapsulated counterpart strains M variant and Smith compact. Growth of the M strain in a medium designed to enhance capsule production did not delay the onset or decrease the rate of lysis of the strain compared with organisms grown in normal medium. Cations did not selectively decrease the rate of lysis of the encapsulated strain, but inhibited the lysis of both the M and M variant strains. Peptidoglycan, the presumed lysostaphin target, isolated from both M and M variant strains was digested by lysostaphin at very similar rates. In contrast to whole cells, cations stimulated the rate of lysostaphin digestion of peptidoglycan. It is concluded that the fraction of lysostaphin active in cell lysis, believed to be a glycylglycine endopeptidase with a molecular weight of about 25,000, passes freely through the capsular layer to its target in the staphylococcal cell wall.

Bacteriolysis↗
PubMed1980

Classification and characteristics of coagulase-negative, methicillin-resistant staphylococci.

Sixty-five clinical isolates of coagulase-negative, methicillin-resistant staphylococci have been classified as Staphylococcus epidermidis (63.0%), "phosphatase-negative S. epidermidis" (12.3%), coagulase-negative Staphylococcus aureus (6.2%), Staphylococcus hemolyticus (6.2%), Staphylococcus hominis (3.1%), and Staphylococcus warneri (1.5%). Five of the organisms (7.7%) could not be classified with certainty as currently recognized species. Novobiocin resistance was encountered in eight of the strains, but these were not classified as the accepted novobiocin-resistant staphylococcal species. Some differences in antibiotic resistance patterns to those typical of methicillin-resistant S. aureus were noted in that, although 29 strains were resistant to methicillin, penicillin, sulfamethizole, streptomycin, and tetracycline, the remainder of the strains were sensitive to streptomycin or tetracycline or both. In a majority of the strains (42 of 65), methicillin susceptibility testing by the disk method at 30 or at 37 degrees C in the presence of NaCl did not appear to enhance resistance expression. Most of the strains produced beta-lactamase (EC 3.5.2.6), but none of the 21 strains tested produced enterotoxin B.

Anti-Bacterial Agents↗
PubMed1979

Inhibition of alternative complement pathway opsonization by group A streptococcal M protein.

Group A streptococcal M protein is known to be antiphagocytic; however, the exact basis for this property has not been established. In this study the hypothesis was tested that cell wall--associated M protein inhibits phagocytosis by interfering with bacterial opsonization. Two strains of group A Streptococcus pyogenes, CS44 (M+) and CS64 (an M- variant of CS44), were radiolabeled, and after incubation in serum these organisms were exposed to human polymorphonuclear leukocytes. Phagocytosis was quantitated by measurement of leukocyte-associated radioactivity. The contributions of complement and of immunoglobulin to streptococcal opsonization were evaluated by use of serum from a variety of sources. The results revealed that the M- strain was efficiently opsonized via the alternative complement pathway in a relative absence of immunoglobulins. In contrast, the M+ strain was poorly opsonized by all sera tested. These findings suggest that streptococcal M protein in some way prevents bacterial opsonization via the alternative complement pathway and that this property of M protein may partly explain its antiphagocytic characteristic.

Antigens, Bacterial↗
PubMed1979

Cryptic peptidoglycan and the antiphagocytic effect of the Staphylococcus aureus capsule: model for the antiphagocytic effect of bacterial cell surface polymers.

The antiphagocytic effect of the Staphylococcus aureus capsule is known to be related to its ability to interfere with opsonization by normal human serum. In this study, evidence is presented with isolated cell surface components which indicates that the capsule hinders opsonization by masking cell wall peptidoglycan. In contrast to intact, encapsulated S. aureus M cells, peptidoglycan particles isolated from the organism were efficiently opsonized by normal human serum and phagocytized by human polymorphonuclear leukocytes. Cell wall particles retaining capsular material were opsonized less efficiently than peptidoglycan. Studies comparing the opsonic capacities of normal, C2-deficient, and heat-inactivated sera led to the conclusion that both the classical and the alternative complement pathways contribute to the opsonization of peptidoglycan in normal human serum. It appears that the capsule interferes with opsonization via both of these complement pathways. Serum from rabbits immunized with S. aureus M had significant heat-stable opsonic activity for the intact organism and cell walls retaining capsular material, but not for peptidoglycan. A general model is proposed to explain how antiphagocytic cell surface polymers may inhibit bacterial opsonization and thereby impede natural immunity.

Cell Wall↗
PubMed1979

Staphylococcus aureus cell surface: capsule as a barrier to bacteriophage adsorption.

Encapsulated Staphylococcus aureus strains M and Smith diffuse bound phage 84 and 52A much less efficiently than their unencapsulated counterparts, M variant and Smith compact. It is proposed that the capsule acts as a barrier excluding phage from interaction with their receptor (cell wall peptidoglycan and teichoic acid). Inefficient phage adsorption by encapsulated staphylococci may explain, in part, the poor phage typing of such strains.

Adsorption↗
PubMed1979

Chemotaxigenesis by cell surface components of Staphylococcus aureus.

In an attempt to delineate the staphylococcal cell surface components of importance in chemotaxigenesis, we incubated intact Staphylococcus aureus H, crude cell walls, purified cell walls, peptidoglycan, teichoic acid, and cell membranes with human sera. The results reported indicate that both crude cell walls and purified cell walls, as well as peptidoglycan, were potent chemotaxigens. These particles led to the generation in normal human serum of a factor that was chemotactic for human polymorphonuclear leukocytes. Cell wall peptidoglycan and teichoic acid both appeared to play a role in chemotaxigenesis. Kinetic studies employing C2-deficient serum and immunoglobulin-deficient serum revealed that optimal chemotaxigenesis required the presence of an intact classical complement pathway, as well as antibody. Granulocyte aggregometry studies showed that significant levels of C5a were generated in normal serum and that this activated complement component appears to be a major chemotactic factor produced in serum upon interaction with staphylococcal cell wall components.

Cell Membrane↗
PubMed1979

Localization of the third component of complement on the cell wall of encapsulated Staphylococcus aureus M: implications for the mechanism of resistance to phagocytosis.

Encapsulated Staphylococcus aureus strains are more virulent than unencapsulated staphylococci, and this phenomenon has been associated with decreased opsonization of encapsulated bacteria by normal human serum. Peptidoglycan, a major cell wall component of S. aureus, has been shown to promote opsonization of this bacterial species by certain components of the serum complement system. However, when the processes of complement activation and opsonization of encapsulated staphylococci have been studied, it has been found that encapsulated bacteria activate complement efficiently and C3 is bacteria associated, yet these organisms are not efficiently phagocytized by human polymorphonuclear leukocytes. In this study, the hypothesis was tested that opsonically active molecules are not on the true external surface of encapsulated organisms but rather are cell wall associated and thus "hidden" from human polymorphonuclear leukocytes. By using immunoelectronmicroscopy, C3 was found to be localized on the cell wall of an encapsulated S. aureus strain after incubation of the organism in normal human serum. When shrinkage of the capsule was prevented by treatment with anticapsular antibody, the C3 was again shown to be cell wall associated and located beneath the bacterial capsule. These results suggest that encapsulated S. aureus may resist phagocytosis because opsonically active C3 molecules are not exposed at the true external surface of the bacterium.

Animals↗
PubMed1978

Characterization and identification of coagulase-negative, heat-stable deoxyribonuclease-positive staphylococci.

Various characteristics of 13 coagulase-negative, weakly heat-stable deoxyribonuclease-positive staphylococci from human, veterinary and food sources were determined in an effort to identify them. Nine of the isolates were identified as coagulase-negative Staphylococcus aureus (2), Staphylococcus xylosus (2), Staphylococcus simulans (3), Staphylococcus capitis (1) and Staphylococcus sciuri subsp. lentus (1); the other four isolates, from food and veterinary sources, could not be identified as currently accepted or proposed species. Teichoic acid and peptidoglycan compositions were used as key taxonomic characteristics. The determination of heat-stable deoxyribonuclease activity can be useful to detect coagulase-negative S. aureus strains. However, this activity also appears to be present in strains of other staphylococcal species.

Coagulase↗
PubMed1978

Influence of encapsulation on staphylococcal opsonization and phagocytosis by human polymorphonuclear leukocytes.

In previous studies, encapsulated Staphylococcus aureus strains have been shown to resist phagocytosis. In this investigation, the nature of the interference with phagocytosis by human polymorphonuclear leukocytes was examined by studying the opsonization of two pairs of unencapsulated (Smith compact and M variant) and encapsulated (Smith diffuse and M) S. aureus strains. The uptake of [3H]glycine-labeled bacteria by normal leukocytes was quantitatively measured after incubation of bacteria in pooled serum, C2-deficient serum, immunoglobulin-deficient serum, and serum from a rabbit immunized with S. aureus M. The presence of a capsule was found to interfere with opsonization by both the classical and alternative pathways of complement as well as by heat-stable opsonic factors in nonimmune human serum. This interference was significantly greater in the case of the S. aureus M strain than in the case of the Smith diffuse strain. The only effective opsonic source for S. aureus M was immune rabbit serum. It is proposed that encapsulation of S. aureus strains interferes with phagocytosis by preventing effective bacterial opsonization.

Antibodies, Bacterial↗
PubMed1978

Activation of complement by cell surface components of Staphylococcus aureus.

The abilities of intact Staphylococcus aureus H, crude cell walls (CCW), purified cell walls (PCW, peptidoglycan [PG] and covalently linked teichoic acid), peptidoglycan, and cell membranes (CM) to activate the complement system in normal human serum, C2-deficient serum, and immunoglobulin-deficient serum were compared. On a weight basis, PCW was the most active fraction; intact organisms and CCW were about equally effective; and PG was least active in causing complement consumption in normal serum. CM also activated complement but did not give a clear dose-response relationship in the concentrations used. Kinetic studies revealed that C3-C9 consumption occurred at a significantly slower rate in C2-deficient serum, indicating that intact organisms, PCW, and PG may activate the complement system via the classical and alternative pathways in normal serum. C3-C9 consumption was also slower in immunoglobulin-deficient serum than in normal serum, implying that immunoglobulins play a role in attaining maximum rates of complement activation. In all sera studied, PG was less active in complement activation than PCW. These results indicate that a number of cell surface components of S. aureus can play a role in complement activation by this organism and that the presence of teichoic acid has a significant enhancing effect in this regard.

Cell Membrane↗
PubMed1978

Dichotomy between opsonization and serum complement activation by encapsulated staphylococci.

Previous studies have demonstrated that encapsulated Staphylococcus aureus strains are not effectively opsonized by the serum complement system. Encapsulated staphylococci thereby "resist phagocytosis." To test whether this phenomenon might be explained by an inability of encapsulated strains to activate complement, the relationship between staphylococcal opsonization and serum complement activation was studied. Although encapsulation was found to interfere with opsonization by pooled human serum (human polymorphonuclear leukocytes phagocytized significantly fewer encapsulated bacteria than unencapsulated bacteria after incubation in this opsonic source), encapsulated (S. aureus M and Smith diffuse) and unencapsulated (S. aureus M variant and Smith compact) strains had similar capacities for complement activation as measured by C3-C9 consumption. When C2-deficient and immunoglobulin-deficient sera were studied, again C3-C9 consumption was not influenced by the presence or absence of a capsule. In addition, C3 was detected on the surface of both S. aureus M and M variant strains after incubation in pooled serum and staining with fluorescein-conjugated anti-C3 antibody. Thus, encapsulated staphylococci are not effectively opsonized even though complement is activated and C3 is present on the bacterial surface. The exact mechanism by which the capsule interferes with opsonization is still not known; however, inhibition of complement activation appears not to be the explanation of this phenomenon.

Antibodies↗
PubMed1978

Cell wall composition and associated properties of methicillin-resistant Staphylococcus aureus strains.

Methicillin-resistant (MR) Staphylococcus aureus strains have previously been reported to be deficient in surface negative charge; this has been correlated with methicillin resistance and ascribed to a deficiency of teichoic acid at the cell surface (A. W. Hill and A. M. James, Microbios 6:157-167, 1972). Teichoic acid was present in walls of MR organisms as revealed by appreciable phosphate levels and detection of ribitol residues. Phosphate levels in walls from five MR strains (0.54 to 0.77 mumol/mg of wall) were lower than in three unrelated methicillin-sensitive (MS) strains (0.86 to 1.0 mumol/mg of wall). However, two MS strains derived from two of the MR strains had wall phosphate levels very similar to those of the MR strains. No evidence for unusual wall polymers was found. Simple deficiency of wall teichoic acid does not result in methicillin resistance since an independently isolated teichoic acid-deficient strain (0.1 mumol of phosphate per mg of wall) was not methicillin resistant. In studies of biological properties possibly related to wall teichoic acid, it was discovered that walls isolated from MR organisms grown in the presence of methicillin autolyzed more rapidly than those isolated from organisms grown in the absence of the drug. Since methicillin resistance is enhanced by NaCl and suppressed by ethylenediaminetetraacetate, the effects of these compounds on autolysis of isolated walls were studied. NaCl (1.0 M) and ethylenediaminetetraacetate (1.0 mM) inhibited the autolysis of walls isolated from MR and MS strains. An MR strain bound phage 47, 52A, and 3A only slightly less well than their respective propagating strains.

Amino Acids↗
PubMed1978

The key role of peptidoglycan in the opsonization of Staphylococcus aureus.

In an effort to determine the staphylococcal cell surface component(s) of importance in opsonization, cell walls (peptidoglycan and teichoic acid) and peptidoglycan were isolated from Staphylococcus aureus strain H grown in [3H]glycine-containing broth. After incubation of the cell walls and peptidoglycan with various opsonic sources, uptake by human polymorphonuclear leukocytes was measured. The opsonic requirements for phagocytosis of cell walls and peptidoglycan were found to be similar to those of intact bacteria. Removal of teichoic acid from the cell wall did not affect opsonization. Likewise, a teichoic acid-deficient mutant strain of S. aureus H was opsonized in a manner similar to that of the parent strain. Immunoglobulin G functioned as the major heat-stable opsonic factor and both the classical and alternative pathways participated in opsonization. Kinetic studies revealed that opsonization of peptidoglycan, as well as C3-C9 consumption by peptidoglycan, proceeded at a slower rate via the alternative pathway (C2-deficient serum) than when the classical pathway was present (normal serum). The ability of peptidoglycan to activate C3-C9 was significantly reduced when normal and C2-deficient sera were preabsorbed with peptidoglycan at 2 degrees C suggesting that antibodies to peptidoglycan may be involved in activation of both the classical and alternative complement pathways. Thus, peptidoglycan appears to be the key cell wall component involved in staphylococcal opsonization, and it is suggested that host response to peptidoglycan, a major cell wall component of most gram-positive bacteria, may be related to the development of "natural immunity" to this group of microorganisms.

Cell Wall↗
PubMed1977

Cyanide-resistant electron transport in sporulating Bacillus megaterium KM.

The NADH oxidase activity of stage V mother-cell membranes, isolated from sporulating Bacillus megaterium KM, shows a greater inhibition by cyanide and displays this response at lower concentrations of cyanide than the stage V forespore inner membrane. Comparison of the effects of various respiratory inhibitors reveals that the difference in cyanide sensitivity between these membranes is located on the oxidase side of the 2-heptyl-4-hydroxyquinoline N-oxide-sensitive step. Both membranes contain cytochromes a+a3, b-562, b-555, c and d, with three potential oxidases: cytochromes a+a3, o and d. Cyanide difference spectra suggest that cytochromes b-562 and d may be the components involved in the cyanide-resistant electron transport pathway. Membrane ascorbate-N,N,N',N'-tetramethylphenylenediamine and ascorbate 2,6-dichlorophenolindophenol oxidase activities are highly sensitive to cyanide. Evidence is presented for terminal branching of the respiratory chain with branches differing in cyanide sensitivity. The cyanide sensitivity of the NADH oxidase of membranes prepared from various stages of sporulation is compared. Morphogenesis of the mother-cell plasma membrane to a cyanide-sensitive form during stages II and III of sporulation is postulated.

Bacillus megaterium↗