Use of fibrinolytic agents to coat wire implants to decrease infection. An animal model

Novel dalbavancin-PLLA implant coating prevents hematogenous Staphylococcus aureus infection in a minimally invasive mouse tail vein model

Infective/bacterial endocarditis is a rare but life-threatening disease with a hospital mortality rate of 22.7% and a 1-year mortality rate of 40%. Therefore, continued research efforts to develop efficient anti-infective implant materials are of the utmost importance. Equally important is the development of test systems that allow the performance of new materials to be comprehensively evaluated. In this study, a novel antibacterial coating based on dalbavancin was tested in comparison to rifampicin/minocycline, and the suitability of a recently developed mouse tail vein model for testing the implant coatings was validated. Small polymeric stent grafts coated with a poly-L-lactic acid (PLLA) layer and incorporated antibiotics were colonized with Staphylococcus (S.) aureus before implantation into the tail vein of mice. The main assessment criteria were the hematogenous spread of the bacteria and the local tissue reaction to the contaminated implant. For this purpose, colony-forming units (CFU) in the blood, spleen and kidneys were determined. Tail cross sections were prepared for histological analysis, and plasma cytokine levels and expression values of inflammation-associated genes were examined. Both antibiotic coatings performed excellently, preventing the onset of infection. The present study expands the range of available methods for testing the anti-infectivity of cardiovascular implants, and the spectrum of agents for effective surface coating.

Microbial biofilm in human health - an updated theoretical and practical insight

The term biofilm designates an aggregate of microorganisms belonging to one or more species which adhere to various surfaces but also to each another. These microbial communities are included and interconnected within an organic structure known as slime, composed of protein substances, polysaccharides, and DNA.

The Center for Disease prevention and control considers infections with bacteria in biofilms among the 7 most important challenges which must be overcome in order to improve the safety of health services. The risk of microbial biofilm development exists for a long list of medical devices and equipment, as well as in certain diseases such as cystic fibrosis. An aggravating aspect is represented by the almost 1,000 times higher antimicrobial resistance of bacteria growing and multiplying within biofilms. Thus, in case of biofilm-infected medical devices, the resistance to antimicrobial treatments requires the removal of the device which essentially means the failure of the exploratory or therapeutic intervention in question.

The role of microbial biofilms in medical pathology is a subject that raises interest for both researchers and clinicians in order to establish new methods for prevention and treatment of biofilms. This paper is intended as an overview in the management of microbial biofilms, presenting future insights, with technological progress in microscopy, molecular genetics, and genome analysis. Therefore the present paper will focus on describing the mechanisms involved in biofilm development, biofilm related infections, methods of detection and quantification of microbial communities and therapeutical approaches.

Bacterial adherence and biofilm formation on medical implants: a review

Biofilms are a complex group of microbial cells that adhere to the exopolysaccharide matrix present on the surface of medical devices. Biofilm-associated infections in the medical devices pose a serious problem to the public health and adversely affect the function of the device. Medical implants used in oral and orthopedic surgery are fabricated using alloys such as stainless steel and titanium. The biological behavior, such as osseointegration and its antibacterial activity, essentially depends on both the chemical composition and the morphology of the surface of the device. Surface treatment of medical implants by various physical and chemical techniques are attempted in order to improve their surface properties so as to facilitate bio-integration and prevent bacterial adhesion. The potential source of infection of the surrounding tissue and antimicrobial strategies are from bacteria adherent to or in a biofilm on the implant which should prevent both biofilm formation and tissue colonization. This article provides an overview of bacterial biofilm formation and methods adopted for the inhibition of bacterial adhesion on medical implants.

Drenaje de colecciones abscesificadas abdominales. Ventajas del uso de fibrinolíticos

Image-guided percutaneous abscess drainage has become the standard method of treatment for most abdominal abscesses. In many cases, it should be considered the treatment of choice, but there are certain circumstances that require specific approaches and methods. Typical abscesses within solid parenchymal organs or those in the peritoneal spaces can be reliably detected by imaging techniques and efficiently drained. Abscesses that are multiple or long and circuitous require careful placement of one or more catheters. Management of the drainage catheters includes irrigation with saline solution to prevent obstruction. Despite the use of saline irrigations and large caliber catheters, catheter drainage sometimes fails and conventional surgery is required. In selected cases, fibrinolytic agents have been proved to be effective in shortening drainage times and length of hospital stay. The use of fibrinolytic agents in the drainage of some anatomical sites, such as the spleen and pancreas, is controversial and the technique should be meticulously selected. Successful treatment is most likely when an interdisciplinary approach is used. The present article reviews the state of the art of the use of fibrinolytic agents to improve percutaneous abdominal abscess drainage.

[Animal models of osteomyelitis]

Despite new approaches in biochemical testing, radiologic and nuclear medicine and advances in surgical techniques, the problem of diagnosis and therapy of acute and chronic osteitis has not been finally solved. Clinical research on osteitis is problematic as there are many variables influencing the inflammatory process and a wide spectrum in therapeutic options exists, hampering research under defined conditions. Consequently, there was an early need for animal models. In vivo experimental settings were established to gain reproducible and reliable results under standardized conditions on the pathogenesis and therapy of osteitis. In this article, an overview of the hitherto established experimental animal models and the results of osteitis research on these models is given.

Computed Tomography-guided Drainage of Intra-abdominal Infections

Image-guided percutaneous abscess drainage has become a standard method of treatment of most abdominal abscesses. In most cases, it should be considered the treatment of choice, but there are selected areas and circumstances that require specific approaches and methods. Typical abscesses within solid parenchyma organs or those in the peritoneal spaces can be reliably detected and efficiently drained. Abscesses that are multiple or long and circuitous require careful placement of catheters. Management of the drainage catheters includes irrigation with fluid to minimize accumulations of material that may impair egress of fluid. In selected cases, fibrinolytic agents have proved effective in shortening the drainage times and shortening hospital stays. Some controversial areas such as splenic abscesses, pancreatic abscesses, echinococcal abscesses, and fungal abscesses should only be attempted with careful selection and meticulous technique. Successful treatment is most likely with candid consultation among the various clinical services.

Does endotoxin contribute to aseptic loosening of orthopedic implants?

Aseptic loosening of orthopedic implants caused by wear particles is a major clinical problem. This review examines the hypothesis that bacterial endotoxin contributes to aseptic loosening. Clinical findings support this hypothesis: bacterial biofilms exist on many implants from patients with aseptic loosening and antibiotics in bone cement reduce the rate of aseptic loosening. Three approaches were used to demonstrate that adherent endotoxin increases bioactivity of titanium particles. These experiments measured cytokine production and osteoclast differentiation in vitro and murine calvarial osteolysis in vivo. First, removal of >99.9% of the adherent endotoxin from titanium particles significantly ablates their biological activity. Second, adding lipopolysaccharide back to these "endotoxin-free" particles restores their biological activity. Third, cells or mice that are genetically hyporesponsive to endotoxin are significantly less responsive to titanium particles than are wild-type controls. Other investigators have confirmed and extended these results to include virtually all orthopedically relevant types of particles, including authentic titanium alloy particles retrieved from patients with loosening. Our recent studies suggest that adherent endotoxin on orthopedic implants may also inhibit initial osseointegration of the implants. Taken together, these studies suggest that bacterial endotoxin may have a significant role in induction of aseptic loosening.

Adhesion of Staphylococcus to orthopaedic metals, an in vivo study

This study describes a new model of biofilm study in rabbits. The primary focus of this study was to assess biofilm adhesion to orthopaedic metals in their first 48 h in a femoral intramedullary implantation model. Two previous inoculation methods i.e. that of pre- and direct inoculation were studied with two bacterial isolates namely Staphylococcus aureus and epidermidis, on titanium and stainless steel metallic implants. A method of sonication and log dilution/plating was used to assess biofilm bacteria adhering to implants. Silver coated metals were then compared with their respective control metals in the new model. The direct inoculation model gave larger and more reproducible biofilm adhesion to implanted metals. Staphylococcus epidermidis shows lower adhesion ability to metals, and biofilms adhere in greater numbers to stainless steel over titanium. Silver coated metals show no statistical difference over control metals when exposed to orthopaedic biofilms.

Adherent endotoxin on orthopedic wear particles stimulates cytokine production and osteoclast differentiation

Aseptic loosening of orthopedic implants is thought to be caused primarily by osteoclast differentiation induced by bone resorptive cytokines produced in response to phagocytosis of implant-derived wear particles. This study examined whether adherent endotoxin on the wear particles is responsible for inducing osteoclast differentiation as well as production of interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor a (TNF-alpha). Removal of adherent endotoxin almost completely inhibited the responses to titanium (Ti) particles by both murine marrow cells and human peripheral blood monocytes. In vivo experiments showed that endotoxin removal reduced particle-induced osteolysis by 50-70%. Addition of lipopolysaccharide (LPS) to the "endotoxin-free" particles restored their ability to induce cytokine production and osteoclast differentiation in vitro. Moreover, marrow cells from mice that are hyporesponsive to endotoxin because of mutation of Toll-like receptor 4 induced significantly less cytokine production and osteoclast differentiation in response to Ti particles with adherent endotoxin than did marrow cells from normoresponsive mice. This mutation also resulted in significantly less particle-induced osteolysis in vivo. Taken together, these results show that adherent endotoxin is involved in many of the biological responses induced by orthopedic wear particles and should stimulate development of new approaches designed to reduce the activity of adherent endotoxin in patients with orthopedic implants.

Intracavitary urokinase for enhancement of percutaneous abscess drainage: phase II trial

OBJECTIVE

To evaluate the effectiveness of urokinase as an abscess-cavity irrigant during percutaneous abscess drainage.

SUBJECTS AND METHODS

In a prospective study, approved by the Food and Drug Administration and the review board at our institution, urokinase and saline were used as abscess-cavity irrigants. In the study group of 42 patients, half the patients were randomly placed into the urokinase group and the other half were placed into the control saline group. Doses used varied with the size of the abscess. Data collected from patient charts were evaluated with standard statistical methods.

RESULTS

The results indicate definite benefits of the urokinase treatment. The length of stay (p = 0.0025) and treatment costs (p = 0.0021) were significantly less for the urokinase group. Other clinical parameters, including the febrile course, elevated WBC, and days of drainage, trended in a favorable fashion.

CONCLUSION

Urokinase injected intracavitarily is an effective technique for shortening the treatment time and improves the clinical course for patients treated with percutaneous drainage techniques.

Animal models of orthopedic implant infection

Prosthetic infection following total joint replacement can have catastrophic results both physically and psychologically for patients, leading to complete failure of the arthroplasty, possible amputation, prolonged hospitalization, and even death. Although with the use of prophylactic antibiotics and greatly improved operating room techniques the infection rate has decreased markedly during the years, challenges still remain for better preventive and therapeutic measures. In this review the in vivo experimental methods for studies of prosthetic infection are discussed, concentrating on (1) the animal models that have been established and the use of these animal models for studies of pathogenesis of bacteria, behavior of biofilm, effect of biomaterials on prosthetic infection rate, and the effect of infection on biomaterial surfaces, and (2) how to design and conduct an animal model of orthopedic prosthetic infection including animal selection, implant fabrication, bacterial inoculation, surgical technique, and the methods for evaluating the results.