Biomedical subjects

Llinos G Harris

Publications and source records attributed to Llinos G Harris.

6 recordsLinked to original sources

PubMed2006

Polysaccharide intercellular adhesin or protein factors in biofilm accumulation of Staphylococcus epidermidis and Staphylococcus aureus isolated from prosthetic hip and knee joint infections.

Nosocomial staphylococcal foreign-body infections related to biofilm formation are a serious threat, demanding new therapeutic and preventive strategies. As the use of biofilm-associated factors as vaccines is critically restricted by their prevalence in natural staphylococcal populations we studied the distribution of genes involved in biofilm formation, the biofilm phenotype and production of polysaccharide intercellular adhesin (PIA) in clonally independent Staphylococcus aureus and Staphylococcus epidermidis strains isolated from prosthetic joint infections after total hip or total knee arthroplasty. Biofilm formation was detected in all S. aureus and 69.2% of S. epidermidis strains. Importantly, 27% of biofilm-positive S. epidermidis produced PIA-independent biofilms, in part mediated by the accumulation associated protein (Aap). Protein-dependent biofilms were exclusively found in S. epidermidis strains from total hip arthroplasty (THA). In S. aureus PIA and proteins act cooperatively in biofilm formation regardless of the infection site. PIA and protein factors like Aap are of differential importance for the pathogenesis of S. epidermidis in prosthetic joint infections (PJI) after THA and total knee arthroplasty (TKA), implicating that icaADBC cannot serve as a general virulence marker in this species. In S. aureus biofilm formation proteins are of overall importance and future work should focus on the identification of functionally active molecules.

Adhesins, Bacterial↗

PubMed2006

Microbial interactions in Staphylococcus epidermidis biofilms.

Medical device-associated infections, most frequently caused by coagulase-negative staphylococci, especially Staphylococcus epidermidis, are of increasing importance in modern medicine. The formation of adherent, multilayered bacterial biofilms is the most important factor in the pathogenesis of these infections, which regularly fail to respond to appropriate antimicrobial therapy. Progress in elucidating the factors functional in elaboration of S. epidermidis biofilms and the regulation of their expression with a special emphasis on the role of quorum sensing are reviewed. Significant progress has been made in recent years, which provides the rationale for developing better preventive, therapeutic and diagnostic measures.

Bacterial Physiological Phenomena↗

PubMed2006

Staphylococci and implant surfaces: a review.

Surfaces of internal fracture fixation implants are generally designed to encourage soft- and/or hard-tissue adherence, eventually leading to tissue or osseo integration. Unfortunately, this feature may also encourage bacterial adhesion. About half of the two million cases of nosocomial infections per year in the US are associated with indwelling devices. In the UK, implant-associated infections are estimated to cost pound 7-11 million per year, and with the rise in antibiotic-resistant bacteria, are an important issue. Soft-tissue infections and osteomyelitis are serious complications associated with implants, particularly open fractures, external fixation devices, and intramedullary nailing. Consequences of implant-associated infections include prolonged hospitalization with systemic antibiotic therapy, several revision procedures, possible amputation, and even death. This review discusses the issue of implant-associated infections and some of the methods used to prevent bacterial adhesion to osteosynthesis implants.

Bacterial Adhesion↗

PubMed2005

Assessment of the cytocompatibility of different coated titanium surfaces to fibroblasts and osteoblasts.

Over the years, many metal and polymer implants have been developed for internal fracture fixation. However, there are always some problems associated with their application, such as implant loosening or infection. This study describes how the morphology and adhesion of both fibroblasts and osteoblasts to two manufactured commercially pure, medical implant-quality anodized titanium surfaces (TS and TSS), and five modified titanium surfaces (TLF, low friction gray anodized titanium; TIG, nitrogen ion implanted TSS; THY, TSS grafted with sodium hyaluronate; TAST, TSS coated with hydrophilic hydrogel; and TT, tiodized TS) were used to obtain an indication of their relative cytocompatibility and to assess which modified surface could potentially be used in vivo. Small variations were observed both qualitatively and quantitatively in the spreading and adhesion of fibroblasts and osteoblasts to the studied surfaces. Overall, fibroblast spreading and adhesion were greatest on the TIG and TLF surfaces. Osteoblast spreading and adhesion were greatest on TS, TIG, and TAST surfaces. No fibroblasts or osteoblasts were found attached to the THY-coated surfaces. Coating medical implant-quality anodized titanium surfaces (TS and TSS) with a TLF, TAST, or more specifically TIG could probably improve soft tissue adhesion and/or osseointegration of bone in vivo. However, it seemed that a hyaluronic acid coating (THY) has potential as a coating in areas where cell adhesion is undesirable, such as orbital fractures, where muscles should avoid adhesion to the implant, and distal radius fractures, where tendons should freely glide over the implant.

Animals↗

PubMed2005

Influence of contrast media (iopromide, ioxaglate, gadolinium-DOTA) on blood viscosity, erythrocyte morphology and platelet function.

The influence of contrast media on blood viscosity, erythrocyte morphology and platelet function was studied. In vitro blood was incubated with iopromide (Ultravist), ioxaglate (Hexabrix) or gadolinium-DOTA (Dotarem). Plasma viscosity and whole blood viscosity were measured and the mean erythrocyte volume and morphology were assessed. Platelet aggregation was measured with a PFA-100 instrument. In an ex vivo study on patients receiving these contrast media the same measurements as described above were done. All contrast media increased blood viscosity at high shear rate in a dose dependent manner (e.g. with ioxaglate: from 4.9+/-0.2 mPa x s to 8.6+/-0.5 mPa x s at 160 mg I/ml), decreased low shear viscosity (for ioxaglate: from 44.9+/-2.5 to 27.7+/-4.8 mPa x s), increased plasma viscosity (ioxaglate: from 1.2+/-0.1 to 2.8+/-1.3 mPa x s), decreased the mean erythrocytic volume (ioxaglate: from 89.7+/-1.4 to 79.7+/-2.0 fl) and decreased platelet aggregation. Iopromide induced an echinocytic shape transformation of erythrocytes. Ex vivo a decreased hematocrit and a consecutively decreased whole blood viscosity were found with iopromide and ioxaglate. We conclude that contrast media influenced blood rheology, erythrocytes and platelet aggregation in vitro and ex vivo.

Adult↗

PubMed2002

Analysis of Ebh, a 1.1-megadalton cell wall-associated fibronectin-binding protein of Staphylococcus aureus.

In order for Staphylococcus aureus to adhere to host extracellular matrix (ECM) substrates, it elicits a wide range of surface proteins. We have characterized a novel approximately 1.1-MDa protein in S. aureus, termed Ebh (for ECM-binding protein homologue), which has homology to other ECM-binding proteins. Ebh consists of several domains, including a large central region with 44 imperfect repeats of 126 amino acids. Expression analysis revealed ebh to be growth phase regulated and repressed by agr. A fragment of the central repeat region of Ebh was cloned, overexpressed, and used in ligand-binding studies to determine Ebh function. The recombinant protein was found to specifically bind human fibronectin. Ebh is produced during human infection since serum samples taken from patients with confirmed S. aureus infections were found to contain anti-Ebh antibodies. Localization studies revealed Ebh to be cell envelope associated and is proposed to form a specialized surface structure involved in cellular adhesion.

Abscess↗