Biomedical subjects

Mathias Herrmann

Publications and source records attributed to Mathias Herrmann.

30 records · Page 2Linked to original sources

PubMed2004

Staphylococcus aureus fibronectin-binding protein (FnBP)-mediated adherence to platelets, and aggregation of platelets induced by FnBPA but not by FnBPB.

BACKGROUND: The ability of Staphylococcus aureus to adhere to platelets and to induce aggregation of platelets is considered to be a critical factor in S. aureus-associated infective endocarditis. METHODS: To identify and characterize further bacterial factors involved in the S. aureus-platelet interaction, we generated a phage-display library of S. aureus genomic DNA by use of the improved phagemid vector pG8SAET. The library was affinity-panned against gel-filtered, immobilized platelets. RESULTS: Repeatedly isolated clones contained overlapping DNA fragments encoding a portion of the S. aureus fibronectin (Fn)-binding proteins (FnBPs). In a flow cytometric adherence assay, Staphylococcus carnosus that heterologously expressed either fnbA or fnbB, which encode FnBPA and FnBPB, respectively, showed increased adherence to activated, gel-filtered platelets. Adherence was promoted by the addition of Fn or fibrinogen (Fg), which most likely act as bridging molecules. Interestingly, promotion of adherence mediated by Fn was in the same range with S. carnosus producing either FnBPA or FnBPB, whereas promotion of adherence mediated by Fg was significantly more pronounced with S. carnosus that produce FnBPA than with S. carnosus that produce FnBPB. Furthermore, FnBPA, but not FnBPB, mediated aggregation of platelets when present on S. carnosus cells. CONCLUSION: Our results indicate a substantial functional difference between FnBPA and FnBPB in the S. aureus-platelet interaction.

Adhesins, Bacterial↗

PubMed2004

Soluble fibrin is the main mediator of Staphylococcus aureus adhesion to platelets.

BACKGROUND: Infective endocarditis (IE) caused by Staphylococcus aureus is associated with significant morbidity and mortality rates. Platelets play a dual role as adhesive cells forming associates with bacteria as well as specialized inflammatory cells. The specific role of the various factors involved in bacteria-platelet association has not yet been fully elucidated. METHODS AND RESULTS: We observed a dramatic increase in the capability to bind S aureus when platelets were activated with thrombin (from 5% to 30%, P<0.001). To pinpoint platelet-binding sites involved in the interaction, platelets from knockout mice and from patients with selective inherited deficiency of membrane proteins or of granules were used. CD36, GPIIb/IIIa, and P-selectin were excluded as receptors for S aureus. Platelets from patients with alpha-delta-storage pool disease and Gray platelet syndrome indicate the requirement of alpha-granule contents. Platelet activation by ADP did not promote platelet-S aureus associate formation, although these platelets were covered with bound fibrinogen. Only small numbers of associates between fibrinogen-covered bacteria and ADP-activated platelets were observed. Formation of fibrin alone was also not sufficient to induce association. Only when fibrin formation and platelet activation occurred together were large numbers of associates formed (P<0.001). A potential receptor for fibrin on S aureus is clumping factor A. Addition of thrombospondin-1 to control platelets increased the number of associates (P=0.02). CONCLUSIONS: Soluble fibrin but not fibrinogen is the main mediator of platelet-S aureus association. In addition, platelet activation and the release of alpha-granule contents, particularly thrombospondin-1, is a requirement for platelet-S aureus association.

Adenosine Diphosphate↗

PubMed2004

Mechanisms of biofilm formation in Staphylococcus epidermidis and Staphylococcus aureus: functional molecules, regulatory circuits, and adaptive responses.

Biomaterial-associated infections, most frequently caused by Staphylococcus epidermidis and Staphylococcus aureus, are of increasing importance in modern medicine. Regularly, antimicrobial therapy fails without removal of the implanted device. The most important factor in the pathogenesis of biomaterial-associated staphylococcal infections is the formation of adherent, multilayered bacterial biofilms. In this review, recent insights regarding factors functional in biofilm formation of S. epidermidis, their role in pathogenesis, and regulation of their expression are presented. Similarly, in S. aureus the biofilm mode of growth affects gene expression and the overall metabolic status. Experimental approaches for analysis of differential expression of genes involved in these adaptive responses and evolving patterns of gene expression are discussed.

Adaptation, Physiological↗

PubMed2003

The adhesive and immunomodulating properties of the multifunctional Staphylococcus aureus protein Eap.

Adherence of Staphylococcus aureus to the host tissue is an important step in the initiation of pathogenesis. At least 10 adhesins produced by S. aureus have been described and it is becoming clear that the expression of these adhesins and their interactions with eukaryotic cells involve complex processes. Some of these, such as the fibronectin-binding proteins (FnBPs) and Clumping Factor A, are well characterized. However, in the last 10 years a number of novel S. aureus adhesins have been described. Functional analyses of these proteins, one of which is Eap (extracellular adherence protein, also known as Map and p70), are revealing important information on the pathogenesis of staphylococcal disease. More than 10 years after the first report of Eap, we are beginning to understand that this protein, which has a broad spectrum of functions, may be a critical factor in the pathogenesis of S. aureus. This review will focus on the interactions of Eap with eukaryotic cells, plasma proteins and the extracellular matrix as well as on the recently recognized role of Eap as an important mediator in the immune response to staphylococcal infection.

Adhesins, Bacterial↗

PubMed2003

Extracellular adherence protein from Staphylococcus aureus enhances internalization into eukaryotic cells.

In this study we have shown that Eap (extracellular adherence protein) plays a role in the internalization process of Staphylococcus aureus into eukaryotic cells. Eap is a protein that is mostly extracellularly and to a lesser extent is bound to the bacterial surface as a result of rebinding. Eap is able to bind to several plasma proteins, such as fibronectin, fibrinogen, and prothrombin. It has the capacity to form oligomers and is able to agglutinate S. aureus. A mutant strain, Newman mAH12 (eap:: Ery(r)), with a deficient eap gene was used in the present study. We have demonstrated that (i) strain Newman mAH12 could adhere to and become internalized to a higher extent by eukaryotic cells than the isogenic mutant, (ii) strain Newman mAH12 complemented with the eap gene displayed restoration of the internalization level, (iii) externally added Eap enhanced the internalization of laboratory and clinical S. aureus strains as well as of S. carnosus (a coagulase-negative species devoid of proteins important for internalization), and (iv) antibodies against Eap were able to block the internalization process in strain Newman mAH12 and clinical isolates. Eap, with its broad binding capacity and its surface localization, thus seems to contribute to the internalization of S. aureus into eukaryotic cells. We therefore propose a novel internalization pathway for S. aureus in which Eap plays an enhancing role.

Adhesins, Bacterial↗

PubMed2003

Thymidine-dependent small-colony variants of Staphylococcus aureus exhibit gross morphological and ultrastructural changes consistent with impaired cell separation.

Thymidine-dependent small-colony variants (SCV) of Staphylococcus aureus exhibited unusual colony morphology with "fried-egg" or pinpoint white colonies on agar plates and pleomorphic cocci as determined by Gram staining. Electron microscopy revealed enlarged cocci with incomplete or multiple cross walls consistent with impaired cell separation. Fried-egg SCV phenotypes could be reversed by thymidine supplementation.

Cell Division↗

PubMed2003

Population dynamics of persistent Staphylococcus aureus isolated from the airways of cystic fibrosis patients during a 6-year prospective study.

Molecular typing of normal (n = 456) and small-colony-variant (SCV; n = 239) Staphylococcus aureus isolates cultured from the airways of 52 of 72 cystic fibrosis (CF) patients (72.2%) during a 6-year prospective study revealed a median long-term persistence of 37 months (range, 6 to 70). SCV persisted longer in the airways than the normal S. aureus (statistically not significant). Pulsed-field gel electrophoresis identified six prevalent clonal lineages, which were cultured from more than one patient (3 to 12 patients), and 39 individual clones, which were isolated only from single patients. The SCV phenotype was not restricted to a distinct clonal lineage but occurred in many different clones. Most patients (33 of 52, 63.46%) harbored single clones. This study provides a basis for improved understanding of S. aureus colonization and infection dynamics in CF patients.

Adolescent↗

PubMed2003

Salicylic acid: an old dog, new tricks, and staphylococcal disease.

Aspirin has been shown to cause a reduction in the virulence of Staphylococcus aureus-associated endocarditis. A new study reveals that salicylic acid, the major metabolite of aspirin, acts at the level of transcription to downregulate the production of fibrinogen, fibronectin, and alpha-hemolysin - virulence factors necessary for bacterial replication in host tissues and, now, potential therapeutic targets.

Anti-Bacterial Agents↗

PubMed2003

New aspects of integrin-mediated leukocyte adhesion in inflammation: regulation by haemostatic factors and bacterial products.

Leukocyte recruitment to sites of inflammation, infection or vascular injury is a complex event, depending on a tightly coordinated sequence of leukocyte-endothelial- and leukocyte-platelet interactions, which are controlled by the expression and activation of various adhesion receptors and protease systems. The present review will focus on novel aspects of the regulation of integrin-dependent leukocyte adhesion by haemostatic factors and bacterial products. In particular, after a short overview of leukocyte recruitment, the review (i) will focus on the crosstalk between haemostatic factors and adhesion molecules with respect to leukocyte extravasation based on the paradigms of the urokinase receptor and high molecular weight kininogen, (ii) will provide information on novel mechanisms for the regulation of leukocyte recruitment by bacterial proteins, on the basis of the anti-inflammatory role of Staphylococcus aureus extracellular adhesive protein and (iii) will draw attention to the junctional adhesion molecules, a novel family of adhesive receptors that are counter-receptors for leukocyte integrins and mediate vascular cell interactions. The better understanding of the interactions between vascular cells and particularly of integrin-dependent leukocyte adhesion may lead to the development of novel therapeutical concepts in inflammatory vascular disorders.

Animals↗

PubMed2002

Staphylococcus aureus extracellular adherence protein serves as anti-inflammatory factor by inhibiting the recruitment of host leukocytes.

Staphylococcus aureus is a human pathogen that secretes proteins that contribute to bacterial colonization. Here we describe the extracellular adherence protein (Eap) as a novel anti-inflammatory factor that inhibits host leukocyte recruitment. Due to its direct interactions with the host adhesive proteins intercellular adhesion molecule 1 (ICAM-1), fibrinogen or vitronectin, Eap disrupted beta(2)-integrin and urokinase receptor mediated leukocyte adhesion in vitro. Whereas Eap-expressing S. aureus induced a 2 3-fold lower neutrophil recruitment in bacterial peritonitis in mice as compared with an Eap-negative strain, isolated Eap prevented beta(2)-integrin-dependent neutrophil recruitment in a mouse model of acute thioglycollate-induced peritonitis. Thus, the specific interactions with ICAM-1 and extracellular matrix proteins render Eap a potent anti-inflammatory factor, which may serve as a new therapeutic substance to block leukocyte extravasation in patients with hyperinflammatory pathologies.

Animals↗

PubMed2002

Platelet-binding domains in 2 fibrinogen-binding proteins of Staphylococcus aureus identified by phage display.

The adherence of microorganisms to platelets previously immobilized on the subendocardium in nonbacterial thrombotic endocarditis is considered an important pathogenic step in Staphylococcus aureus endocarditis. To identify and characterize bacterial factors involved in the adherence to platelets, a phage display library of S. aureus was generated by use of the phagemid pG8H6. The library was affinity panned against purified immobilized platelets. After a second panning against platelets, a significant increase in the number of eluted phagemid particles was observed; 27% of 88 randomly isolated clones expressed overlapping deduced amino acid sequences with high similarity to the C-terminal domain of the S. aureus coagulase. In addition, 22% of the clones expressed the N-terminal domain of the fibrinogen-binding protein Efb. The surface-associated fraction of the C-terminal domain of coagulase or the N-terminal domain of Efb may be involved in bacterial adherence to immobilized platelets, and fibrinogen may act as a bridging molecule in that interaction.

Bacterial Adhesion↗

PubMed2002

Insertional inactivation of Eap in Staphylococcus aureus strain Newman confers reduced staphylococcal binding to fibroblasts.

To initiate invasive infection, Staphylococcus aureus must adhere to host substrates, such as the extracellular matrix or eukaryotic cells, by virtue of different surface proteins (adhesins). Recently, we identified a 60-kDa cell-secreted extracellular adherence protein (Eap) of S. aureus strain Newman with broad-spectrum binding characteristics (M. Palma, A. Haggar, and J. I. Flock, J. Bacteriol. 181:2840-2845, 1999), and we have molecularly confirmed Eap to be an analogue of the previously identified major histocompatibility complex class II analog protein (Map) (M. Hussain, K. Becker, C. von Eiff, G. Peter, and M. Herrmann, Clin. Diagn. Lab. Immunol. 8:1281-1286, 2001). Previous analyses of the Eap/Map function performed with purified protein did not allow dissection of its precise role in the complex situation of the staphylococcal whole cell presenting several secreted and wall-bound adhesins. Therefore, the role of Eap was investigated by constructing a stable eap::ermB deletion in strain Newman and by complementation of the mutant. Patterns of extracted cell surface proteins analyzed both by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by Western ligand assays with various adhesive matrix molecules clearly confirmed the absence of Eap in the mutant. However, binding and adhesion tests using whole staphylococcal cells demonstrated that both the parent and mutant strains bound equally well to fibronectin- and fibrinogen-coated surfaces, possibly due to their recognition by other staphylococcal adhesins. Furthermore, Eap mediated staphylococcal agglutination of both wild-type and mutant cells. In contrast, the mutant adhered to a significantly lesser extent to cultured fibroblasts (P < 0.001) than did the wild type, while adherence was restorable upon complementation. Furthermore, adherence to both epithelial cells (P < 0.05) and fibroblasts (not significant) could be blocked with antibodies against Eap, whereas preimmune serum was not active. In conclusion, Eap may contribute to pathogenicity by promoting adhesion of whole staphylococcal cells to complex eukaryotic substrates.

Adhesins, Bacterial↗