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1.
Z Evid Fortbild Qual Gesundhwes ; 141-142: 53-61, 2019 May.
Article in German | MEDLINE | ID: mdl-31072809

ABSTRACT

BACKGROUND: In Germany, the final year of medical school consists of a series of clinical externships termed "Practical Year" (PY). Logbooks have been introduced to document the clinical experience and the value of the teaching program (First Ordinance amending the Licensing Regulations for Physicians, July 14, 2012). However, little is known about how PY education is experienced by students, what problems they face, what support they seek to manage their problems, and how the logbooks contribute to training. OBJECTIVE: We assessed the PY education at the Charité Medical School (University Medicine Berlin) in terms of the requirement profile, quality of training, logbooks, satisfaction, and general conditions. MATERIAL AND METHODS: We developed a questionnaire to assess PY education by relying on medical students' experiences. This tool was developed in parallel with the introduction of the logbooks. We contacted 6,068 students between May 2014 to September 2017 via e-mail. The students were asked to participate in the evaluation on a voluntary basis and answer 39 questions. The questionnaire was completed using an anonymous online form, taking into account legal data protection regulations. RESULTS: We evaluated 1,957 questionnaires (31.1 %). The students were mostly satisfied (67.6 %) with their supervision. Patient encounters were, for the most part (85.5 %), perceived as informative, and the quality of continuing education as high (91.3 %), and most students (76.1 %) were directly involved in patient care. The students (87.8 %) felt that they had made progress during the PY teaching period, although the logbooks were rarely (14 %) used and apparently not reviewed by the teaching staff. The students judged some rotations harshly when they were dissatisfied with both teaching and supervision. CONCLUSIONS: In general, the PY experience at the Charité was rated positively. Some rotations receiving poor evaluations desperately need to be reviewed. The role of the logbook seems to be imperfectly defined. The survey results suggest that further evaluation of our program is needed with ongoing participation of students and their representatives.


Subject(s)
Curriculum , Education, Medical, Undergraduate , Internship and Residency , Students, Medical , Adult , Berlin , Female , Germany , Humans , Male , Schools, Medical , Universities
3.
Article in English | MEDLINE | ID: mdl-27158224

ABSTRACT

Osteoarthritis (OA) might affect chondrocyte culture characteristics and complement expression. Therefore, this study addressed the interrelation between macroscopical and microscopical structure, complement expression, and chondrocyte culture characteristics in non-OA and OA cartilage. Femoral head cartilage samples harvested from patients with femoral neck fractures (FNFs) and OA were analyzed for macroscopical alterations using an in-house scoring system, graded histologically (Mankin score), and immunolabeled for complement regulatory proteins (CRPs) and receptors. Morphology of monolayer cultured chondrocytes isolated from a subset of samples was assessed. The macroscopical score distinguished the FNF and OA cartilage samples and correlated significantly with the histological results. Chondrocyte phenotype from FNF or OA cartilage differed. Complement receptor C5aR, CRPs CD55 and CD59, and weakly receptor C3AR were detected in the investigated FNF and OA cartilage, except for CD46, which was detected in only two of the five investigated donors. The in-house score also allows inexperienced observers to distinguish non-OA and OA cartilage for experimental purposes.

4.
Cells Tissues Organs ; 201(5): 354-65, 2016.
Article in English | MEDLINE | ID: mdl-27160711

ABSTRACT

Tissue-engineered intervertebral discs (IVDs) utilizing decellularized extracellular matrix (ECM) could be an option for the reconstruction of impaired IVDs due to degeneration or injury. The objective of this study was to prepare a cell-free decellularized human IVD scaffold and to compare neotissue formation in response to recellularization with human IVD cells (hIVDCs) or human bone marrow-derived (hBM) mesenchymal stromal cells (MSCs). IVDs were decellularized via freeze-thaw cycles, detergents and trypsin. Histological staining was performed to monitor cell removal and glycosaminoglycan (GAG) removal. The decellularized IVD was preconditioned using bovine serum albumin and fetal bovine serum before its cytocompatibility for dynamically cultured hBM-MSCs (chondrogenically induced or not) and hIVDCs was compared after 14 days. In addition, DNA, total collagen and GAG contents were assessed. The decellularization protocol achieved maximal cell removal, with only few remaining cell nuclei compared with native tissue, and low toxicity. The DNA content was significantly higher in scaffolds seeded with hIVDCs compared with native IVDs, cell-free and hBM-MSC-seeded scaffolds (p < 0.01). The GAG content in the native tissue was significantly higher compared to the others groups except for the scaffolds reseeded with chondrogenically induced hBM-MSCs (p < 0.05). In addition, there was a significantly increased total collagen content in the chondrogenically induced hBM-MSCs group (p < 0.01) compared with the native IVDs, cell-free and hIVDC-seeded scaffolds (p < 0.01); both recolonizing cell types were more evenly distributed on the scaffold surface, but only few cells penetrated the scaffold. The resulting decellularized ECM was cytocompatible and allowed hBM-MSCs/hIVDCs survival and ECM production.


Subject(s)
Bone Marrow Cells/cytology , Chondrogenesis , Extracellular Matrix/metabolism , Intervertebral Disc/cytology , Mesenchymal Stem Cells/cytology , Aged , Aged, 80 and over , Cell Survival , Cell-Free System , Collagen/metabolism , DNA/metabolism , Female , Glycosaminoglycans/metabolism , Humans , Male , Middle Aged , Staining and Labeling
5.
Inflamm Res ; 64(11): 917-28, 2015 Nov.
Article in English | MEDLINE | ID: mdl-26350038

ABSTRACT

INTRODUCTION: Inflammatory processes driven by cytokines play a crucial role during osteoarthritis (OA) progression. Dendritic polyglycerol sulfate (dPGS) was analyzed in vitro for its effects on articular chondrocytes, cartilage and cytokines involved in the OA process. METHODS: The metabolic activity of cultured human articular chondrocytes stimulated for 24 h with dPGS (10(-3)-10(-6) mol/L) was monitored using AlamarBlue(®) assay. The dPGS uptake was studied using fluorescence labeled nanoparticles. Further, chondrocytes were either treated with 10(-6) M dPGS, TNFα (10 ng/mL) alone or with a combination of both. The influence on extracellular matrix components, pro- and anti-inflammatory cytokines, matrix metalloproteinase (MMP)1 and the anaphylatoxin receptor C3aR was analyzed by RTD-PCR, flow cytometry and ELISA. RESULTS: Even at higher dosages (10(-3) mol/L), dPGS did not influence chondrocytes viability. Uptake of dPGS was successfully monitored in human articular chondrocytes and synovial fibroblasts, penetration into cartilage chips was up to ~50 µm. Cellular treatment with dPGS had no effect on synthesis of pro-inflammatory cytokines TNFα and IL-6, but expression of the anti-inflammatory IL-10 was upregulated. Cotreatment with TNFα and dPGS reduced the TNFα level, while IL-1ß, IL-6 and IL-10 expression did not change. Collagen type II gene expression was significantly reduced after preincubating cells with dPGS, but remained unaffected at the protein level. CONCLUSION: Results indicate that dPGS could play a role in regulation of cytokines associated with the inflammatory aspect of OA progression.


Subject(s)
Chondrocytes/drug effects , Dendrimers/pharmacology , Glycerol/pharmacology , Polymers/pharmacology , Aged , Aged, 80 and over , Animals , Cartilage, Articular/cytology , Cell Line , Cells, Cultured , Chondrocytes/metabolism , Collagen Type II/genetics , Collagen Type II/metabolism , Cytokines/metabolism , Extracellular Matrix/metabolism , Female , Fibroblasts/metabolism , Gene Expression Regulation/drug effects , Humans , Male , Mice , Middle Aged , Swine
7.
Mater Sci Eng C Mater Biol Appl ; 50: 160-72, 2015 May.
Article in English | MEDLINE | ID: mdl-25746258

ABSTRACT

To overcome the limited intrinsic cartilage repair, autologous chondrocyte or bone-marrow-derived mesenchymal stromal cell (BM-MSC) was implanted into cartilage defects. For this purpose suitable biocompatible scaffolds are needed to provide cell retention, chondrogenesis and initial mechanical stability. The present study should indicate whether a recently developed highly porous alginate (Alg) foam scaffold supplemented with chondroitin sulfate (CS) allows the attachment, survival and chondrogenesis of BM-MSCs and articular chondrocytes. The foams were prepared using a freeze-drying method; some of them were supplemented with CS and subsequently characterized for porosity, biodegradation and mechanical profile. BM-MSCs were cultured for 1-2 weeks on the scaffold either under chondrogenic or maintenance conditions. Cell vitality assays, histology, glycosaminoglycan (sGAG) assay, and type II and I collagen immunolabelings were performed to monitor cell growth and extracellular matrix (ECM) synthesis in the scaffolds. Scaffolds had a high porosity ~93-95% with a mean pore sizes of 237±48 µm (Alg) and 197±61 µm (Alg/CS). Incorporation of CS increased mechanical strength of the foams providing gradually CS release over 7 days. Most of the cells survived in the scaffolds. BM-MSCs and articular chondrocytes formed rounded clusters within the scaffold pores. The BM-MSCs, irrespective of whether cultured under non/chondrogenic conditions and chondrocytes produced an ECM containing sGAGs, and types II and I collagen. Total collagen and sGAG contents were higher in differentiated BM-MSC cultures supplemented with CS than in CS-free foams after 14 days. The cell cluster formation induced by the scaffolds might stimulate chondrogenesis via initial intense cell-cell contacts.


Subject(s)
Alginates/pharmacology , Chondrogenesis/drug effects , Chondroitin Sulfates/pharmacology , Mesenchymal Stem Cells/cytology , Aged , Aged, 80 and over , Cartilage, Articular/cytology , Cell Differentiation/drug effects , Cell Proliferation/drug effects , Cell Survival/drug effects , Cells, Cultured , Chondrocytes/cytology , Collagen Type I/metabolism , Collagen Type II/metabolism , DNA/metabolism , Female , Glucuronic Acid/pharmacology , Glycosaminoglycans/metabolism , Hexuronic Acids/pharmacology , Humans , Male , Mesenchymal Stem Cells/drug effects , Middle Aged , Porosity , Spectrometry, X-Ray Emission , Spectroscopy, Fourier Transform Infrared , Tissue Scaffolds/chemistry
8.
Int J Mol Sci ; 15(9): 15821-44, 2014 Sep 09.
Article in English | MEDLINE | ID: mdl-25207597

ABSTRACT

Chondrogenic differentiated mesenchymal stromal cells (MSCs) are a promising cell source for articular cartilage repair. This study was undertaken to determine the effectiveness of two three-dimensional (3D) culture systems for chondrogenic MSC differentiation in comparison to primary chondrocytes and to assess the effect of Interleukin (IL)-10 and Tumor Necrosis Factor (TNF)α on chondrogenesis by MSCs in 3D high-density (H-D) culture. MSCs were isolated from femur spongiosa, characterized using a set of typical markers and introduced in scaffold-free H-D cultures or non-woven polyglycolic acid (PGA) scaffolds for chondrogenic differentiation. H-D cultures were stimulated with recombinant IL-10, TNFα, TNFα + IL-10 or remained untreated. Gene and protein expression of type II collagen, aggrecan, sox9 and TNFα were examined. MSCs expressed typical cell surface markers and revealed multipotency. Chondrogenic differentiated cells expressed cartilage-specific markers in both culture systems but to a lower extent when compared with articular chondrocytes. Chondrogenesis was more pronounced in PGA compared with H-D culture. IL-10 and/or TNFα did not impair the chondrogenic differentiation of MSCs. Moreover, in most of the investigated samples, despite not reaching significance level, IL-10 had a stimulatory effect on the type II collagen, aggrecan and TNFα expression when compared with the respective controls.


Subject(s)
Chondrocytes/cytology , Chondrogenesis , Interleukin-10/pharmacology , Mesenchymal Stem Cells/cytology , Tumor Necrosis Factor-alpha/metabolism , Aggrecans/genetics , Aggrecans/metabolism , Cells, Cultured , Chondrocytes/drug effects , Chondrocytes/metabolism , Collagen Type II/genetics , Collagen Type II/metabolism , Humans , Mesenchymal Stem Cells/drug effects , Mesenchymal Stem Cells/metabolism , Polyglycolic Acid/pharmacology , SOX9 Transcription Factor/genetics , SOX9 Transcription Factor/metabolism , Tumor Necrosis Factor-alpha/genetics , Tumor Necrosis Factor-alpha/pharmacology
9.
IEEE Comput Graph Appl ; 33(1): 70-4, 2013.
Article in English | MEDLINE | ID: mdl-24807883

ABSTRACT

In a workshop, high school students built a virtual world for a car-racing game. The prerequisites were math-rather than programming-skills; instructional scaffolding (OpenGL templates and tutors) aided students through their programming tasks. This workshop was an alternative to other measures (for example, Microsoft's recent campaign) to get high school students interested in computer science.


Subject(s)
Computer Graphics , Informatics/education , Students , User-Computer Interface , Adolescent , Female , Germany , Humans , Imaging, Three-Dimensional , Male , Mathematics
10.
Cell Tissue Res ; 350(3): 465-75, 2012 Dec.
Article in English | MEDLINE | ID: mdl-23053049

ABSTRACT

Tissue trauma induces an inflammatory response associated with a cytokine release that may engage complement pathways. Cytokine-mediated complement expression may contribute to cartilage degradation. Hence, we analysed the complement expression profile in primary articular and non-articular chondrocytes and its interrelation with cytokines. The expression of the anaphylatoxin receptors (C3aR and C5aR) and the complement regulatory proteins (CPRs) CD35, CD46, CD55 and CD59 was studied in cultured articular, auricular and nasoseptal chondrocytes using RTD-PCR and immunofluorescence labelling. The complement profile of peripheral blood mononuclear cells (PBMCs) was opposed to the expression in articular chondrocytes. The time-dependent regulation (6 and 24 h) of these complement factors was assessed in articular chondrocytes in response to the cytokines TNFα, IL-10 or TNFα combined with IL-10 (each 10 ng/mL). C3aR, C5aR, CD46, CD55 and CD59 but almost no CD35 mRNA was expressed in any of chondrocyte types studied. The anaphylatoxin receptor expression was lower and that of the CRPs was higher in chondrocytes when compared with PBMCs. The majority of the studied complement factors were expressed at a significantly lower level in non-articular chondrocytes compared with the articular chondrocytes. TNFα significantly increased the C3aR expression in chondrocytes after 6 and 24 h. TNFα + IL-10 significantly downregulated C5aR and IL-10 significantly inhibited the CD46 and CD55 gene expression after 24 h. C5aR and CD55 could be localised in cartilage in situ. Anaphylatoxin receptors and CRPs are regulated differentially by TNFα and IL-10. Whether cytokine-induced complement activation occurs in response to cartilage trauma has to be further identified.


Subject(s)
Antigens, CD/biosynthesis , Cartilage, Articular/metabolism , Chondrocytes/metabolism , Interleukin-10/pharmacology , Receptor, Anaphylatoxin C5a/biosynthesis , Receptors, Complement/biosynthesis , Tumor Necrosis Factor-alpha/pharmacology , Aged , Aged, 80 and over , Antigens, CD/genetics , Cartilage, Articular/cytology , Cartilage, Articular/drug effects , Cells, Cultured , Chondrocytes/cytology , Chondrocytes/drug effects , Complement System Proteins/biosynthesis , Complement System Proteins/genetics , Female , Fluorescent Antibody Technique, Indirect , Gene Expression , Humans , Immunohistochemistry , Leukocytes/metabolism , Male , Middle Aged , RNA, Messenger/biosynthesis , RNA, Messenger/genetics , Receptor, Anaphylatoxin C5a/genetics , Receptors, Complement/genetics
11.
Acta Orthop Belg ; 73(5): 571-9, 2007 Oct.
Article in English | MEDLINE | ID: mdl-18019911

ABSTRACT

This is a retrospective study of the results of angle-stable plating of displaced 3- or 4- part fractures of the proximal humerus in 92 geriatric patients treated between 2/2000 and 2/2004. At final follow-up patients were clinically evaluated using the Constant-Murley score and were examined radiologically. The mean non-age-related Constant-Murley score was 69.8 points. A clear correlation was found between the final score and the quality of reposition of the tuberosities and/or plate position. Accurate reduction and plate positioning led to a significantly better functional result. For 28 patients (30.4%), sinkage of the humeral head into the shaft occurred despite angle-stable anchoring. The currently celebrated angle-stabilising plates did not lead to a significant improvement in functional outcome, compared with other established osteosynthesis procedures.


Subject(s)
Bone Plates , Fracture Fixation, Internal , Fracture Healing/physiology , Shoulder Fractures/surgery , Humans , Humerus , Joint Dislocations/diagnostic imaging , Joint Dislocations/physiopathology , Joint Dislocations/surgery , Postoperative Complications , Radiography , Range of Motion, Articular , Retrospective Studies , Shoulder Fractures/diagnostic imaging , Shoulder Fractures/physiopathology , Trauma Severity Indices
12.
Acta Orthop ; 78(1): 63-73, 2007 Feb.
Article in English | MEDLINE | ID: mdl-17453394

ABSTRACT

INTRODUCTION: Local application of growth factors to stimulate wound and fracture healing is attracting increasing interest. We studied the effect of local application of a potent angiogenic growth factor, basic fibroblast growth factor (bFGF), on resistance to local infection after soft tissue trauma. METHODS: For in-vitro and in-vivo experiments, we used recombinant human bFGF. The in-vitro investigations were performed by isolation of human leukocyte fractions, cytokine analysis, phagocytosis assay, flow cytometry, and LDH assay. For the in-vivo investigation, a paired comparison of infection rates was carried out on Sprague-Dawley rats after standardized, closed soft tissue trauma and local, percutaneous bacterial inoculation of different concentrations of Staphylococcus aureus (2 x 10(4) to 2 x 10(7) colony-forming units (cfu)). The lower leg was treated with 1, 10 or 100 ng bFGF (16 animals for each concentration) and without bFGF (16 animals). RESULTS: Cytotoxic reactions due to the concentrations of bFGF used could be excluded in the in-vitro tests since incubations of isolated peripheral blood mononuclear cells (PBMCs) with increasing concentrations of bFGF for 24 h did not lead to an increase in the release of lactate dehydrogenase in the culture supernatants compared to corresponding control incubations without any bFGF added. A significant increase in cytokine release was observed after the co-incubation of PBMCs with 100 or 200 ng of the same bFGF that was used for the animal experiments. Furthermore, the capacity of phagocytes in whole blood to phagocytose bacteria was suppressed in the presence of 100 ng exogenously added bFGF. We found continuously reduced granulocytic phagocytosis in FGF-supplemented blood compared to non-supplemented blood. In the in-vivo investigation, the infection rate for the group without bFGF was 0.25. In the groups with 1, 10 and 100 ng bFGF, the infection rates were 0.5, 0.7 and 0.8, respectively. A dose-dependent increase in infection rate was observed after local application of bFGF, compared to the untreated control group. The difference in infection rates for the groups in which 10 and 100 ng bFGF was used, relative to the group without bFGF, was statistically significant. INTERPRETATION: If these initial results are confirmed for other potent angiogenic growth factors, then the local use of growth factors for stimulation of wound and bone healing--a main focus of current research in traumatology--will have to be reconsidered and preceded with a strict evaluation of the risks and benefits.


Subject(s)
Bacterial Infections/etiology , Fibroblast Growth Factor 2/administration & dosage , Soft Tissue Injuries/complications , Wound Healing/drug effects , Administration, Topical , Animals , Bacterial Infections/immunology , Bacterial Infections/microbiology , Cytokines/metabolism , Fibroblast Growth Factor 2/adverse effects , Humans , In Vitro Techniques , Leukocytes/immunology , Male , Phagocytosis/drug effects , Rats , Rats, Sprague-Dawley , Risk Factors , Soft Tissue Injuries/immunology , Soft Tissue Injuries/microbiology , Wound Healing/immunology
13.
J Orthop Res ; 24(8): 1622-40, 2006 Aug.
Article in English | MEDLINE | ID: mdl-16779814

ABSTRACT

The purpose of this study was to acquire information about the effect of an antibacterial and biodegradable poly-L-lactide (PLLA) coated titanium plate osteosynthesis on local infection resistance. For our in vitro and in vivo experiments, we used six-hole AO DC minifragment titanium plates. The implants were coated with biodegradable, semiamorphous PLLA (coating about 30 microm thick). This acted as a carrier substance to which either antibiotics or antiseptics were added. The antibiotic we applied was a combination of Rifampicin and fusidic acid; the antiseptic was a combination of Octenidin and Irgasan. This produced the following groups: Group I: six-hole AO DC minifragment titanium plate without PLLA; Group II: six-hole AO DC minifragment titanium plate with PLLA without antibiotics/antiseptics; Group III: six-hole AO DC minifragment titanium plate with PLLA + 3% Rifampicin and 7% fusidic acid; Group IV: six-hole AO DC minifragment titanium plate with PLLA + 2% Octenidin and 8% Irgasan. In vitro, we investigated the degradation and the release of the PLLA coating over a period of 6 weeks, the bactericidal efficacy of antibiotics/antiseptics after their release from the coating and the bacterial adhesion of Staphylococcus aureus to the implants. In vivo, we compared the infection rates in white New Zealand rabbits after titanium plate osteosynthesis of the tibia with or without antibacterial coating after local percutaneous bacterial inoculations at different concentrations (2 x 10(5)-2 x 10(8)): The plate, the contaminated soft tissues and the underlying bone were removed under sterile conditions after 28 days and quantitatively evaluated for bacterial growth. A stepwise experimental design with an "up-and-down" dosage technique was used to adjust the bacterial challenge in the area of the ID50 (50% infection dose). Statistical evaluation of the differences between the infection rates of both groups was performed using the two-sided Fisher exact test (p < 0.05). Over a period of 6 weeks, a continuous degradation of the PLLA coating of 13%, on average, was seen in vitro in 0.9% NaCl solution. The elution tests on titanium implants with antibiotic or antiseptic coatings produced average release values of 60% of the incorporated antibiotic or 62% of the incorporated antiseptic within the first 60 min. This was followed by a much slower, but nevertheless continuous, release of the incorporated antibiotic and antiseptic over days and weeks. At the end of the test period of 42 days, 20% of the incorporated antibiotic and 15% of the incorporated antiseptic had not yet been released from the coating. The antibacterial effect of the antibiotic/antiseptic is not lost by integrating it into the PLLA coating. The overall infection rate in the in vivo investigation was 50%. For Groups I and II the infection rate was both 83% (10 of 12 animals). In Groups III and IV with antibacterial coating, the infection rate was both 17% (2 of 12 animals). The ID50 in the antibacterial coated Groups III and IV was recorded as 1 x 10(8) CFU, whereas the ID50 values in the Groups I and II without antibacterial coating were a hundred times lower at 1 x 10(6) CFU, respectively. The difference between the groups with and without antibacterial coating was statistically significant (p = 0.033). Using an antibacterial biodegradable PLLA coating on titanium plates, a significant reduction of infection rate in an in vitro and in vivo investigation could be demonstrated. For the first time, to our knowledge, we were able to show, under standardized and reproducible conditions, that an antiseptic coating leads to the same reduction in infection rate as an antibiotic coating. Taking the problem of antibiotic-induced bacterial resistance into consideration, we thus regard the antiseptic coating, which shows the same level of effectiveness, as advantageous.


Subject(s)
Anti-Bacterial Agents/pharmacokinetics , Anti-Infective Agents, Local/pharmacokinetics , Coated Materials, Biocompatible , Fracture Fixation, Internal , Prosthesis-Related Infections/prevention & control , Absorbable Implants , Animals , In Vitro Techniques , Materials Testing , Microbiological Techniques , Polyesters/pharmacokinetics , Prosthesis-Related Infections/drug therapy , Rabbits , Staphylococcal Infections/drug therapy , Staphylococcal Infections/prevention & control , Staphylococcus aureus/drug effects , Titanium
14.
J Orthop Res ; 21(2): 373-8, 2003 Mar.
Article in English | MEDLINE | ID: mdl-12568972

ABSTRACT

PURPOSE: The etiology of local posttraumatic infection in the locomotor system depends on the amount, virulence and pathogenicity of the inoculated microorganisms and the local/systemic host damage due to the type and extent of the accident or iatrogenic trauma. The relative effect of these factors remains unclear. In particular, it is still unclear today whether--in presence of microorganisms--soft tissue damage and its pathophysiological consequences lead to infection after soft tissue trauma, or whether the bacterial contamination is the primarily cause for posttraumatic infection. The aim of the project was to gain information on the consequences of a soft tissue injury in terms of resistance to local infection. Since clinical populations are too heterogeneous, the problem was investigated in a standardized, reduced (no surgery or implants) experimental in vivo model. METHOD: In female Sprague-Dawley-rats with a standardized closed soft tissue trauma to the tibialis anterior muscle (group I: n=13) or without (group II: n=13), we compared the incidence of local infection after a pairwise local, percutaneously injected bacterial challenge with various concentrations of Staphylococcus aureus (2 x 10(4)-2 x 10(6) colony forming units, CFU). The standardized closed soft tissue trauma was created by application of a specially designed, computer controlled impact device. The contaminated soft tissue and the underlying bone were removed under sterile conditions after five days and quantitatively evaluated for bacterial growths. Infection was defined as positive bacterial growth at the soft tissue and/or bone. A stepwise experimental design with an "up-and-down" dosage technique was used to adjust the bacterial challenge in the area of the ID50 (50% infection dose). Statistical evaluation of the difference between the infection rates of both groups was performed by two-sided fisher exact test (p<0.05). RESULTS: The overall infection rate was 46%. For the group with soft tissue trauma the ID50 was 1.32 x 10(5) CFU and 1.05 x 10(6) CFU for the group without soft tissue trauma. The infection rate was 69% (9 of 13 animals) for the group with soft tissue trauma and 23% (3 of 13 animals) for the group without soft tissue trauma. This difference is statistically significant (p=0.047). CONCLUSIONS: The infection rate after a standardized closed soft tissue injury was significantly higher and the ID50 lower than without soft tissue trauma. Our results demonstrate that in presence of microorganisms it is not primarily the bacterial contamination but rather the soft tissue damage and its pathophysiological consequences resulting in decreased infection resistance that secondarily lead to infection.


Subject(s)
Disease Models, Animal , Muscle, Skeletal/injuries , Soft Tissue Infections/etiology , Soft Tissue Injuries/complications , Animals , Colony Count, Microbial , Female , Hindlimb , Muscle, Skeletal/microbiology , Rats , Rats, Sprague-Dawley , Soft Tissue Infections/microbiology , Soft Tissue Injuries/microbiology , Staphylococcus aureus/pathogenicity , Staphylococcus aureus/physiology , Tibia/injuries , Tibia/microbiology
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