Biomedical subjects

Mathias Herrmann

Publications and source records attributed to Mathias Herrmann.

At least 19 recordsLinked to original sources

PubMed2006

The extracellular adherence protein from Staphylococcus aureus abrogates angiogenic responses of endothelial cells by blocking Ras activation.

The extracellular adherence protein (Eap), a broad-spectrum adhesin secreted by Staphylococcus aureus, was previously shown to curb acute inflammatory responses, presumably through its binding to endothelial cell (EC) ICAM-1. Examining the effect of Eap on endothelial function in more detail, we here show that, in addition, Eap functions as a potent angiostatic agent. Concomitant treatment of EC with purified Eap resulted in the complete blockage of the mitogenic and sprouting responses elicited by vascular endothelial growth factor (VEGF)165 or basic fibroblast growth factor (bFGF). Moreover, the induction of tissue factor and decay-accelerating factor were repressed by Eap, as determined by qRT-polymerase chain reaction (qRT-PCR), with a corresponding reduction in Egr-1 protein up-regulation seen. This angiostatic activity was accompanied by a corresponding inhibition in ERK1/2 phosphorylation, while activation of p38 was not affected. Inhibition occurred downstream of tyrosine kinase receptor activation, as comparable effects were seen on TPA-induced ERK1/2 phosphorylation. Similar to previously described angiostatic agents like angiopoietin-1 or the 16-kDa prolactin fragment, Eap blockage of the Ras/Raf/MEK/ERK cascade was localized by pull-down assay at the level of Ras activation. Eap's combined anti-inflammatory and antiangiogenic properties render this bacterial protein not only an important virulence factor during S. aureus infection but open new perspectives for therapeutic applications in pathological neovascularization.

Bacterial Proteins↗

PubMed2006

Quorum-sensing systems in staphylococci as therapeutic targets.

The staphylococci are an ever-present threat in our world, capable of causing a wide range of infections, and are a persistent presence in the clinical environment. As the number of antimicrobial compounds effective against staphylococci decreases, because of the acquisition and spread of antibiotic resistance, there is a growing need for novel therapeutic molecules. Intra and inter-species communication (quorum sensing) is a biologically significant phenomenon that has been associated with virulence, intracellular survival, and biofilm formation. Quorum sensing molecules of staphylococci and other species (e.g. Pseudomonas aeruginosa) can inhibit virulence factor production and/or growth of staphylococci, leading to the possibility that interference with staphylococcal quorum-sensing systems could be a way of controlling the diverse infections caused by the staphylococci. In this article, we discuss the potential of quorum-sensing systems of staphylococci as therapeutic targets.

Anti-Bacterial Agents↗

PubMed2006

Suppression of experimental autoimmune encephalomyelitis by extracellular adherence protein of Staphylococcus aureus.

Multiple sclerosis (MS) is a devastating inflammatory disorder of the central nervous system (CNS). A major hallmark of MS is the infiltration of T cells reactive against myelin components. T cell infiltration is mediated by the interaction of integrins of the beta1 and beta2 family expressed by lymphocytes with their endothelial counter-receptors, vascular cell adhesion molecule 1 and intercellular adhesion molecule (ICAM)-1, respectively. We have reported previously that extracellular adherence protein (Eap) of Staphylococcus aureus exerts antiinflammatory activities by interacting with ICAM-1 and blocking beta2-integrin-dependent neutrophil recruitment. Here, we report that Eap inhibits experimental autoimmune encephalomyelitis (EAE) in mice. In vitro, Eap reduced adhesion of peripheral blood T cells to immobilized ICAM-1 as well as their adhesion and transmigration of TNF-activated human endothelium under static and shear flow conditions. These inhibitory effects were corroborated in two mouse models of inflammation. In a delayed-type hypersensitivity model, both T cell infiltration and the corresponding tissue edema were significantly reduced by Eap. In addition, Eap administration prevented the development of EAE and markedly decreased infiltration of inflammatory cells into the CNS. Strikingly, intervention with Eap after the onset of EAE suppressed the disease. Collectively, our findings indicate that Eap represents an attractive treatment for autoimmune neuroinflammatory disorders such as MS.

Amino Acid Sequence↗

PubMed2006

The anchorless adhesin Eap (extracellular adherence protein) from Staphylococcus aureus selectively recognizes extracellular matrix aggregates but binds promiscuously to monomeric matrix macromolecules.

Besides a number of cell wall-anchored adhesins, the majority of Staphylococcus aureus strains produce anchorless, cell wall-associated proteins, such as Eap (extracellular adherence protein). Eap contains four to six tandem repeat (EAP)-domains. Eap mediates diverse biological functions, including adherence and immunomodulation, thus contributing to S. aureus pathogenesis. Eap binding to host macromolecules is unusually promiscuous and includes matrix or matricellular proteins as well as plasma proteins. The structural basis of this promiscuity is poorly understood. Here, we show that in spite of the preferential location of the binding epitopes within triple helical regions in some collagens there is a striking specificity of Eap binding to different collagen types. Collagen I, but not collagen II, is a binding substrate in monomolecular form. However, collagen I is virtually unrecognized by Eap when incorporated into banded fibrils. By contrast, microfibrils containing collagen VI as well as basement membrane-associated networks containing collagen IV, or aggregates containing fibronectin bound Eap as effectively as the monomeric proteins. Therefore, Eap-binding to extracellular matrix ligands is promiscuous at the molecular level but not indiscriminate with respect to supramolecular structures containing the same macromolecules. In addition, Eap bound to banded fibrils after their partial disintegration by matrix-degrading proteinases, including matrix metalloproteinase 1. Therefore, adherence to matrix suprastructures by S. aureus can be supported by inflammatory reactions.

Bacterial Adhesion↗

PubMed2006

Small colony variants: a pathogenic form of bacteria that facilitates persistent and recurrent infections.

Small colony variants constitute a slow-growing subpopulation of bacteria with distinctive phenotypic and pathogenic traits. Phenotypically, small colony variants have a slow growth rate, atypical colony morphology and unusual biochemical characteristics, making them a challenge for clinical microbiologists to identify. Clinically, small colony variants are better able to persist in mammalian cells and are less susceptible to antibiotics than their wild-type counterparts, and can cause latent or recurrent infections on emergence from the protective environment of the host cell. This Review covers the phenotypic, genetic and clinical picture associated with small colony variants, with an emphasis on staphylococci, for which the greatest amount of information is available.

Aminoglycosides↗

PubMed2006

[Antimicrobial therapy in dermatology].

The extensive and sometimes indiscriminate use of antibiotics sometimes without strict indications has led to increases in both bacterial resistance and sensitization of patients. Systemic antibiotics in skin infections are indicated when a severe local infection occurs which spreads into the surrounding tissue or when there are signs of systemic infection. There are special indications in patients with peripheral arterial occlusive disease,diabetes or immunosuppression. Topical use of antibiotics should be abandoned and replaced by antiseptics. The beta-lactam antibiotics are the antibiotics of first choice for many skin infections. They are usually effective, have a well-defined profile of adverse events and most are affordable. Penicillin G or V are the first line treatment for erysipelas. Infections with Staphylococcus aureus are usually treated with isoxazolyl penicillins or second generation cephalosporins. In mixed infections in patients with diabetes or peripheral arterial occlusive disease,the treatment of choice is metronidazole plus beta-lactam-/beta-lactamase inhibitor antibiotics, but quinolones or second generation cephalosporins can also be used, once again with metronidazole. The aim of this review is to define the indications for antibiotics in dermatology, to highlight their modes of action and adverse effects and to make suggestions for rational antibiotic therapy in cutaneous infections frequently encountered in the practice of dermatology.

Administration, Topical↗

PubMed2006

Very low ethanol concentrations affect the viability and growth recovery in post-stationary-phase Staphylococcus aureus populations.

Pharmaceuticals, culture media used for in vitro diagnostics and research, human body fluids, and environments can retain very low ethanol concentrations (VLEC) (< or =0.1%, vol/vol). In contrast to the well-established effects of elevated ethanol concentrations on bacteria, little is known about the consequences of exposure to VLEC. We supplemented growth media for Staphylococcus aureus strain DSM20231 with VLEC (VLEC(+) conditions) and determined ultramorphology, growth, and viability compared to those with unsupplemented media (VLEC(-) conditions) for prolonged culture times (up to 8 days). VLEC(+)-grown late-stationary-phase S. aureus displayed extensive alterations of cell integrity as shown by scanning electron microscopy. Surprisingly, while ethanol in the medium was completely metabolized during exponential phase, a profound delay of S. aureus post-stationary-phase recovery (>48 h) was observed. Concomitantly, under VLEC(+) conditions, the concentration of acetate in the culture medium remained elevated while that of ammonia was reduced, contributing to an acidic culture medium and suggesting decreased amino acid catabolism. Interestingly, amino acid depletion was not uniformly affected: under VLEC(+) conditions, glutamic acid, ornithine, and proline remained in the culture medium while the uptake of other amino acids was not affected. Supplementation with arginine, but not with other amino acids, was able to restore post-stationary-phase growth and viability. Taken together, these data demonstrate that VLEC have profound effects on the recovery of S. aureus even after ethanol depletion and delay the transition from primary to secondary metabolite catabolism. These data also suggest that the concentration of ethanol needed for bacteriostatic control of S. aureus is lower than that previously reported.

Aerobiosis↗

PubMed2006

Global regulatory impact of ClpP protease of Staphylococcus aureus on regulons involved in virulence, oxidative stress response, autolysis, and DNA repair.

Staphylococcus aureus is an important pathogen, causing a wide range of infections including sepsis, wound infections, pneumonia, and catheter-related infections. In several pathogens ClpP proteases were identified by in vivo expression technologies to be important for virulence. Clp proteolytic complexes are responsible for adaptation to multiple stresses by degrading accumulated and misfolded proteins. In this report clpP, encoding the proteolytic subunit of the ATP-dependent Clp protease, was deleted, and gene expression of DeltaclpP was determined by global transcriptional analysis using DNA-microarray technology. The transcriptional profile reveals a strong regulatory impact of ClpP on the expression of genes encoding proteins that are involved in the pathogenicity of S. aureus and adaptation of the pathogen to several stresses. Expression of the agr system and agr-dependent extracellular virulence factors was diminished. Moreover, the loss of clpP leads to a complete transcriptional derepression of genes of the CtsR- and HrcA-controlled heat shock regulon and a partial derepression of genes involved in oxidative stress response, metal homeostasis, and SOS DNA repair controlled by PerR, Fur, MntR, and LexA. The levels of transcription of genes encoding proteins involved in adaptation to anaerobic conditions potentially regulated by an Fnr-like regulator were decreased. Furthermore, the expression of genes whose products are involved in autolysis was deregulated, leading to enhanced autolysis in the mutant. Our results indicate a strong impact of ClpP proteolytic activity on virulence, stress response, and physiology in S. aureus.

Anaerobiosis↗

PubMed2006

Fibronectin binding proteins contribute to the adherence of Staphylococcus aureus to intact endothelium in vivo.

Staphylococcal adhesins mediate attachment to matrix proteins and endothelial cells in vitro, yet, their role in primary adherence to the physiologic vessel wall has not been studied in vivo, and complex endocarditis models yielded ambiguous results. Recently, we developed a hamster model to study interaction kinetics of S. aureus with intact microvasculature using intravital fluorescence microscopy (Laschke et al. J Infect Dis 2005; 191: 435-443) providing the basis for this study. S. aureus Cowan 1 wild type (WT) log phase cells adhered to postcapillary venules to a significantly larger extent compared to stationary phase staphylococci, a finding in congruence with the fact that the staphylococcal adhesin repertoire largely depends on the growth phase. In comparison, the adherence rate of the fnbA deleted mutant (DU5895) to the vessel wall was significantly reduced to approximately 40% of WT. These DU5895 attachment rates were similar to those of an S. carnosus strain (TM300). In contrast, upon heterologous complementation of TM300 with either fnbA and fnbB, adherence of these transformants to the microvasculature increased, an increase found to be significant for fnbA transformant single cocci and clusters at 30 and 60 min when compared to S. carnosus TM300 WT. In conclusion, these results demonstrate that staphylococcal FnBPs significantly contribute to primary interaction with intact endothelium under physiologic conditions. Accordingly, this attribution of staphylococcal FnBPs provide a rationale for novel intervention strategies such as the use of anti-FnBP antibodies in endovascular S. aureus disease.

Adhesins, Bacterial↗

PubMed2005

The extracellular adherence protein (Eap) of Staphylococcus aureus inhibits wound healing by interfering with host defense and repair mechanisms.

Staphylococcus aureus is a major human pathogen interfering with host-cell functions. Impaired wound healing is often observed in S aureus-infected wounds, yet, the underlying mechanisms are poorly defined. Here, we identify the extracellular adherence protein (Eap) of S aureus to be responsible for impaired wound healing. In a mouse wound-healing model wound closure was inhibited in the presence of wild-type S aureus and this effect was reversible when the wounds were incubated with an isogenic Eap-deficient strain. Isolated Eap also delayed wound closure. In the presence of Eap, recruitment of inflammatory cells to the wound site as well as neovascularization of the wound were prevented. In vitro, Eap significantly reduced intercellular adhesion molecule 1 (ICAM-1)-dependent leukocyte-endothelial interactions and diminished the consequent activation of the proinflammatory transcription factor nuclear factor kappaB (NFkappaB) in leukocytes associated with a decrease in expression of tissue factor. Moreover, Eap blocked alphav-integrin-mediated endothelial-cell migration and capillary tube formation, and neovascularization in matrigels in vivo. Collectively, the potent anti-inflammatory and antiangiogenic properties of Eap provide an underlying mechanism that may explain the impaired wound healing in S aureus-infected wounds. Eap may also serve as a lead compound for new anti-inflammatory and antiangiogenic therapies in several pathologies.

Animals↗

PubMed2005

Fibrinogen and fibronectin binding cooperate for valve infection and invasion in Staphylococcus aureus experimental endocarditis.

The expression of Staphylococcus aureus adhesins in Lactococcus lactis identified clumping factor A (ClfA) and fibronectin-binding protein A (FnBPA) as critical for valve colonization in rats with experimental endocarditis. This study further analyzed their role in disease evolution. Infected animals were followed for 3 d. ClfA-positive lactococci successfully colonized damaged valves, but were spontaneously eradicated over 48 h. In contrast, FnBPA-positive lactococci progressively increased bacterial titers in vegetations and spleens. At imaging, ClfA-positive lactococci were restricted to the vegetations, whereas FnBPA-positive lactococci also invaded the adjacent endothelium. This reflected the capacity of FnBPA to trigger cell internalization in vitro. Because FnBPA carries both fibrinogen- and fibronectin-binding domains, we tested the role of these functionalities by deleting the fibrinogen-binding domain of FnBPA and supplementing it with the fibrinogen-binding domain of ClfA in cis or in trans. Deletion of the fibrinogen-binding domain of FnBPA did not alter fibronectin binding and cell internalization in vitro. However, it totally abrogated valve infectivity in vivo. This ability was restored in cis by inserting the fibrinogen-binding domain of ClfA into truncated FnBPA, and in trans by coexpressing full-length ClfA and truncated FnBPA on two separate plasmids. Thus, fibrinogen and fibronectin binding could cooperate for S. aureus valve colonization and endothelial invasion in vivo.

Adhesins, Bacterial↗

PubMed2005

sae is essential for expression of the staphylococcal adhesins Eap and Emp.

Eap and Emp are two Staphylococcus aureus adhesins initially described as extracellular matrix binding proteins. Eap has since emerged as being important in adherence to and invasion of eukaryotic cells, as well as being described as an immunomodulator and virulence factor in chronic infections. This paper describes the mapping of the transcription start point of the eap and emp promoters. Moreover, using reporter-gene assays and real-time PCR in defined regulatory mutants, environmental conditions and global regulators affecting expression of eap and emp were investigated. Marked differences were found in expression of eap and emp between strain Newman and the 8325 derivatives SH1000 and 8325-4. Moreover, both genes were repressed in the presence of glucose. Analysis of expression of both genes in various regulatory mutants revealed that sarA and agr were involved in their regulation, but the data suggested that there were additional regulators of both genes. In a sae mutant, expression of both genes was severely repressed. sae expression was also reduced in the presence of glucose, suggesting that repression of eap and emp in glucose-containing medium may, in part, be a consequence of a decrease in expression of sae.

Adhesins, Bacterial↗

PubMed2005

Induction of Staphylococcus epidermidis biofilm formation via proteolytic processing of the accumulation-associated protein by staphylococcal and host proteases.

Because of its biofilm forming potential Staphylococcus epidermidis has evolved as a leading cause of device-related infections. The polysaccharide intercellular adhesin (PIA) is significantly involved in biofilm accumulation. However, infections because of PIA-negative strains are not uncommon, suggesting the existence of PIA-independent biofilm accumulation mechanisms. Here we found that biofilm formation in the clinically significant S. epidermidis 5179 depended on the expression of a truncated 140 kDa isoform of the 220 kDa accumulation-associated protein Aap. As expression of the truncated Aap isoform leads to biofilm formation in aap-negative S. epidermidis 1585, this domain mediates intercellular adhesion in a polysaccharide-independent manner. In contrast, expression of full-length Aap did not lead to a biofilm-positive phenotype. Obviously, to gain adhesive function, full-length Aap has to be proteolytically processed through staphylococcal proteases as demonstrated by inhibition of biofilm formation by alpha(2)-macroglobulin. Importantly, also exogenously added granulocyte proteases activated Aap, thereby inducing biofilm formation in S. epidermidis 5179 and four additional, independent clinical S. epidermidis strains. It is therefore reasonable to assume that in vivo effector mechanisms of the innate immunity can directly induce protein-dependent S. epidermidis cell aggregation and biofilm formation, thereby enabling the pathogen to evade clearance by phagocytes.

Adhesins, Bacterial↗

PubMed2005

Thymidine-dependent Staphylococcus aureus small-colony variants are associated with extensive alterations in regulator and virulence gene expression profiles.

Chronic airway infection is a hallmark of cystic fibrosis (CF) and many CF patients are infected persistently by Staphylococcus aureus. Thymidine-dependent trimethoprim-sulfamethoxazole (SXT)-resistant S. aureus small-colony variants (SCVs), often in combination with isogenic normal S. aureus phenotypes, are highly prevalent and persistent in airway secretions of CF patients due to long-term SXT therapy (B. Kahl, M. Herrmann, A. S. Everding, H. G. Koch, K. Becker, E. Harms, R. A. Proctor, and G. Peters, J. Infect. Dis. 177:1023-1029, 1998). In this report, SCVs were compared to normal S. aureus by transcription analysis of important regulator (sigB, sarA, and agr) and virulence (alpha-hemolysin, hla, and protein A, spa) genes. Growth curve analyses revealed longer doubling times and lower final densities for SCVs than for normal strains. sigB activity was measured by transcription analysis of the sigB target gene asp23. For nearly all SCVs, expression of all regulators was decreased as assessed by asp23 reverse transcription-PCR for sigB and Northern analysis for sarA and agr. These results are in agreement with diminished hla signals in all SCVs and increased spa signals in 5 of 10 SCVs compared to the isogenic normal S. aureus. Both supplementation of SCVs with thymidine and activation of the agr quorum-sensing system by the supernatant of the isogenic normal strain reversed transcription to almost normal levels. In conclusion, multiple changes in growth characteristics and in regulator and virulence gene expression render SCVs less virulent and allow them to survive in the hostile environment present in the airways of CF patients, thereby illustrating adaptation of the bacteria during long-term persistence.

Bacterial Proteins↗

PubMed2005

Staphylococcus aureus ClpC is required for stress resistance, aconitase activity, growth recovery, and death.

The ability of Staphylococcus aureus to adapt to various conditions of stress is the result of a complex regulatory response. Previously, it has been demonstrated that Clp homologues are important for a variety of stress conditions, and our laboratory has shown that a clpC homologue was highly expressed in the S. aureus strain DSM20231 during biofilm formation relative to expression in planktonic cells. Persistence and long-term survival are a hallmark of biofilm-associated staphylococcal infections, as cure frequently fails even in the presence of bactericidal antimicrobials. To determine the role of clpC in this context, we performed metabolic, gene expression, and long-term growth and survival analyses of DSM20231 as well as an isogenic clpC allelic-replacement mutant, a sigB mutant, and a clpC sigB double mutant. As expected, the clpC mutant showed increased sensitivity to oxidative and heat stresses. Unanticipated, however, was the reduced expression of the tricarboxylic acid (TCA) cycle gene citB (encoding aconitase), resulting in the loss of aconitase activity and preventing the catabolization of acetate during the stationary phase. clpC inactivation abolished post-stationary-phase recovery but also resulted in significantly enhanced stationary-phase survival compared to that of the wild-type strain. These data demonstrate the critical role of the ClpC ATPase in regulating the TCA cycle and implicate ClpC as being important for recovery from the stationary phase and also for entering the death phase. Understanding the stationary- and post-stationary-phase recovery in S. aureus may have important clinical implications, as little is known about the mechanisms of long-term persistence of chronic S. aureus infections associated with formation of biofilms.

Acetates↗

PubMed2005

Mechanism and consequences of invasion of endothelial cells by Staphylococcus aureus.

It has become clear that Staphylococcus aureus is a facultative intracellular microorganism. Adherence and invasion are a prerequisite for endovascular infections caused by S. aureus, such as infective endocarditis. These phenomena may also be involved in the pathogenesis of invasive and metastatic infection upon hematogenous dissemination, such as osteomyelitis and abscess formation. The underlying molecular mechanism has been elucidated in detail, including its likely relevance in vivo. However, the mode of action of recently identified modulators of invasion, such as pls/Pls have not yet been clarified. The potential outcome for host cells and S. aureus following invasion are diverse. Surprisingly, induction of apoptosis in human endothelial cells is more complex than previously thought, since it appears to involve multiple virulence factors. In the light of increasing resistance to antimicrobial therapy, understanding the multifacetted pathogenesis of S. aureus infection in detail is needed for a better prevention and therapy.

Adhesins, Bacterial↗

PubMed2005

Staphylococcus aureus interactions with the endothelium: the role of bacterial "secretable expanded repertoire adhesive molecules" (SERAM) in disturbing host defense systems.

The intravascular manifestation of Staphylococcus aureus infection is often associated with a severe, and sometimes catastrophic disease. Many host factors contribute to endothelial tropism of S.aureus including subendothelial matrix proteins, endothelial cell receptors, and platelets that are engaged together with S. aureus cell wall adhesins such as the fibronectin binding proteins. Recently, the role of secreted staphylococcal factors that were initially identified by virtue of their binding function with host proteins and ligands, has been reappraised in this regard. Among these, bacterial proteins without significant homology among each other, coagulase (Coa), the extracellular fibrinogen binding protein (Efb), the extracellular matrix binding protein (Emp), or the extracellular adhesive protein (Eap), are the most prominent ones to be associated with endovascular disease. Newly discovered interactions with host components may account for profound effects on immunmodulation and wound healing which are summarized in this short review and which ascribe an important role of these molecules in acute and chronic endo- and extravascular staphylococcal disease. Further research in the complex functional role of these "secretable expanded repertoire adhesive molecules" (SERAM) may not only help to increase our understanding in the pathogenesis of S. aureus infection but can specify novel targets for preventive or therapeutic strategies.

Adhesins, Bacterial↗

PubMed2004

Intravital fluorescence microscopy: a novel tool for the study of the interaction of Staphylococcus aureus with the microvascular endothelium in vivo.

BACKGROUND: The ability of Staphylococcus aureus to adhere to endothelial cells is a major prerequisite for the tissue-invasive stage of bacterial infection. METHODS: To develop a model for the study of endothelial attachment and detachment kinetics of S. aureus within the host's microvasculature in vivo, we labeled inactivated staphylococci with fluorescein isothiocyanate and investigated their interaction with the vascular endothelium of arterioles, capillaries, and venules in the dorsal skin-fold chamber of untreated and tumor necrosis factor (TNF)-alpha-treated hamsters by use of intravital fluorescence microscopy. RESULTS: During the first 20 min after injection, >99% of the bacteria were removed from the microvascular bloodstream. In parallel, single bacteria and bacterial clusters adhered to the endothelial lining of postcapillary venules and to nutritive capillaries. Bacterial adherence to the endothelium of arterioles was only rarely observed. TNF-alpha treatment significantly accelerated bacterial clearance and resulted in a significant increase of venular, but not arteriolar and capillary, bacterial adherence, indicating the venular endothelium to be the target structure for bacterial recruitment. CONCLUSION: The insights into host-pathogen interaction gained with this new in vivo model offer highly promising novel aspects of the understanding of infections caused by S. aureus.

Animals↗