Pathogenese und Praevention von Polymerassoziierten Staphylokokken-Infektionen. Teilprojekt A: Pathogenese von Polymerassoziierten Staphylokokken-Infektionen. Teilprojekt C: Entwicklung und Anwendung eines Kleintiermodelles zur Untersuchung intravasaler Polymer-Infektionen durch Staphylokokken Schlussbericht

The use of implanted foreign material predisposes the host for the development of bacterial infections, in particular infections caused by staphylococcal species. In this project, the following in vitro and in vivo studies have been performed in order to identify mechanisms resulting in bacterial colonization and to evaluate experimental and clinical foreign body infection: 1. In order to examine the adhesion of staphylococci to polymer surfaces, interaction of S. aureus with von Willebrand factor, a protein secreted by platelets and endothelial cells playing a major role in hemostasis, has been studied. In these experiments it could be demonstrated that vWF binds to S. aureus in suspension and promotes the adhesion of S. aureus when preadsorbed to polymeric surfaces. Additional proteins studies include vitronectin and fibronectin. 2. For identification of pathogenic factors of S. epidermidis contributing to polymer associated infections, a mutant lacking a 140-kDa extracellular protein and deficient in accumulative growth (=biofilm formation) has been studied. As demonstrated using protein chemistry and immunologic methods, the 140-kDa protein has been found to be an 'accumulation-associated protein'. 3. An experimental model of intravascular graft infection has been developed using an implant in the rabbit aorta and challenging the animals with intravascular administration of the inoculum. Several polymer materials and several clinical and laboratory S. epidermidis and S. aureus isolates have been evaluated by determination of the infectious dose of a given strain/material combination. It could be shown that intravascular inoculation results in a reproducible infection of the implanted patch material providing for the first time a model in the small animal to investigate pathogenesis, prophylaxis, and therapy of intravascular foreign body infections. 4. In a clinical study, the first 25 patients receiving a left ventricular assist device for bridging the end-stage failing heart until transplantation have been evaluated using modern molecular typing methods of pathogens isolated from significant clinical materials and from the device surfaces at time of explantation. This study provided evidence that the probability of survival to transplant is significantly correlated with infection of the device while an active device infection does not impose a contraindication to transplantation but rather an urgent need for device removal and organ displacement. (orig.)SIGLEAvailable from TIB Hannover: DtF QN1(64,25) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Comparison of 3D segmented gradient-echo and steady-state free precession coronary MRI sequences in patients with coronary artery disease.

OBJECTIVE: Our objective was to compare two state-of-the-art coronary MRI (CMRI) sequences with regard to image quality and diagnostic accuracy for the detection of coronary artery disease (CAD). SUBJECTS AND METHODS: Twenty patients with known CAD were examined with a navigator-gated and corrected free-breathing 3D segmented gradient-echo (turbo field-echo) CMRI sequence and a steady-state free precession sequence (balanced turbo field-echo). CMRI was performed in a transverse plane for the left coronary artery and a double-oblique plane for the right coronary artery system. Subjective image quality (1- to 4-point scale, with 1 indicating excellent quality) and objective image quality parameters were independently determined for both sequences. Sensitivity, specificity, and accuracy for the detection of significant (> or = 50% diameter) coronary artery stenoses were determined as defined in invasive catheter X-ray coronary angiography. RESULTS: Subjective image quality was superior for the balanced turbo field-echo approach (1.8 +/- 0.9 vs 2.3 +/- 1.0 for turbo field-echo; p < 0.001). Vessel sharpness, signal-to-noise ratio, and contrast-to-noise ratio were all superior for the balanced turbo field-echo approach (p < 0.01 for signal-to-noise ratio and contrast-to-noise ratio). Of the 103 segments, 18% of turbo field-echo segments and 9% of balanced turbo field-echo segments had to be excluded from disease evaluation because of insufficient image quality. Sensitivity, specificity, and accuracy for the detection of significant coronary artery stenoses in the evaluated segments were 92%, 67%, 85%, respectively, for turbo field-echo and 82%, 82%, 81%, respectively, for balanced turbo field-echo. CONCLUSION: Balanced turbo field-echo offers improved image quality with significantly fewer nondiagnostic segments when compared with turbo field-echo. For the detection of CAD, both sequences showed comparable accuracy for the visualized segments

Inhomogenities in wall stress measured by microergometry in the heart muscle in situ

Microergometry is a method which we have developed as a tool to measure local mesh-tension within the myocardial weave at any measuring site of both ventricles and the septum on the beating heart in situ. In a mapping procedure on pig and dog hearts, both in control conditions and in the hypertrophied state after aortic banding, local mesh-tension was measured in several areas and in up to eight depths proceeding from the epicardium to the endocardium: Probe-to-fibre coupling is definitely more stable in the canine myocardium than in the porcine heart muscle, probably due to a more effective connective tissue fettering of the canine myocardial weave. The observed longitudinal gradient, with the highest tension in the base, of control dog hearts was levelled out in the hypertrophied hearts. Furthermore, in control dog hearts mesh-tension in the subepi- and subendocardial layers was higher than in the midlayers. This pronounced midlayerhypotension was smoothed in the hypertrophied hearts . Further studies will be dedicated to the question of whether the impact of ventricular size and shape on intersegmental stress transmission is determined by the Frank-Starling mechanism alone or whether protracted remodelling processes on the level of the local fibre weave cause slow coupling alterations