Young Investigator Award. In vivo treatment of infected prosthetic graft material with urokinase: an animal model

Mimicking biofilm formation and development: Recent progress in in vitro and in vivo biofilm models

Biofilm formation in living organisms is associated to tissue and implant infections, and it has also been linked to the contribution of antibiotic resistance. Thus, understanding biofilm development and being able to mimic such processes is vital for the successful development of antibiofilm treatments and therapies. Several decades of research have contributed to building the foundation for developing in vitro and in vivo biofilm models. However, no such thing as an "all fit" in vitro or in vivo biofilm models is currently available. In this review, in addition to presenting an updated overview of biofilm formation, we critically revise recent approaches for the improvement of in vitro and in vivo biofilm models.

Options and Limitations in Clinical Investigation of Bacterial Biofilms

Bacteria can form single- and multispecies biofilms exhibiting diverse features based upon the microbial composition of their community and microenvironment. The study of bacterial biofilm development has received great interest in the past 20 years and is motivated by the elegant complexity characteristic of these multicellular communities and their role in infectious diseases. Biofilms can thrive on virtually any surface and can be beneficial or detrimental based upon the community's interplay and the surface. Advances in the understanding of structural and functional variations and the roles that biofilms play in disease and host-pathogen interactions have been addressed through comprehensive literature searches. In this review article, a synopsis of the methodological landscape of biofilm analysis is provided, including an evaluation of the current trends in methodological research. We deem this worthwhile because a keyword-oriented bibliographical search reveals that less than 5% of the biofilm literature is devoted to methodology. In this report, we (i) summarize current methodologies for biofilm characterization, monitoring, and quantification; (ii) discuss advances in the discovery of effective imaging and sensing tools and modalities; (iii) provide an overview of tailored animal models that assess features of biofilm infections; and (iv) make recommendations defining the most appropriate methodological tools for clinical settings.

From in vitro to in vivo Models of Bacterial Biofilm-Related Infections

The influence of microorganisms growing as sessile communities in a large number of human infections has been extensively studied and recognized for 30–40 years, therefore warranting intense scientific and medical research. Nonetheless, mimicking the biofilm-life style of bacteria and biofilm-related infections has been an arduous task. Models used to study biofilms range from simple in vitro to complex in vivo models of tissues or device-related infections. These different models have progressively contributed to the current knowledge of biofilm physiology within the host context. While far from a complete understanding of the multiple elements controlling the dynamic interactions between the host and biofilms, we are nowadays witnessing the emergence of promising preventive or curative strategies to fight biofilm-related infections. This review undertakes a comprehensive analysis of the literature from a historic perspective commenting on the contribution of the different models and discussing future venues and new approaches that can be merged with more traditional techniques in order to model biofilm-infections and efficiently fight them.

Foreign body infections due to Staphylococcus epidermidis

Staphylococcal infections are one of the main causes of complications in patients with implanted foreign prosthetic material. Implants are associated with a significant reduction of the threshold at which contaminating Gram-positive bacteria, particularly Staphylococcus epidermidis, become infectious and develop a biofilm with phenotypic resistance to almost all antibiotics. A 1000-fold increase in minimal bactericidal levels against most antibiotics except rifampin has been repeatedly observed. Since only removal of the foreign material reverses these phenomena, the clinical challenge consists in finding approaches to cure the infection without removal of the implanted device. Rifampin combinations with other antibiotics, administration of exceedingly high antibiotic concentrations in situ, and early therapy before biofilm development are efficacious. Although these strategies have dramatically improved the outcome of foreign body infections, an improved understanding of biofilm-grown S. epidermidis is necessary to develop new antibacterial agents. Here, we review the pathogenesis, prevention, and treatment of implant infections due to S. epidermidis and highlight some new compounds with already promising in vitro results.

The effect of proteolytic enzyme serratiopeptidase in the treatment of experimental implant-related infection

BACKGROUND

Infection around an implanted orthopaedic device is a devastating complication, and the treatment of infections involving slime-forming bacteria is especially difficult. The purpose of the present study was to evaluate the effectiveness of a proteolytic enzyme, serratiopeptidase, in the eradication of a periprosthetic infection in an in vivo animal model.

METHODS

In sixty Sprague-Dawley rats, the medullary canal of the right femur was drilled through the intercondylar notch and was inoculated with a Staphylococcus epidermidis strain (ATCC 35984) with a high slime-producing capacity. The cavity was filled with polymethylmethacrylate cement, and a Kirschner wire that had contact with the knee joint was inserted. None of the animals received any treatment for two weeks. Twenty rats were killed at two weeks after the inoculation in order to determine if the infection had become established. The remaining forty rats were randomized into two groups. One group received serratiopeptidase enzyme injections into the knee joint in addition to antibiotic therapy for four weeks, and the other group received intra-articular saline solution injections together with the same antibiotic therapy. The animals from both groups were killed two weeks after the end of therapy (on Day 56). The knee specimens were evaluated bacteriologically and histologically to determine the prevalence of persistent infection and the effects of the enzyme on local tissue.

RESULTS

At two weeks, inoculated bacteria grew on culture of specimens from twelve (63.2%) of nineteen animals in the no-treatment group. Microbiological testing suggested that infection persisted in only one (5.6%) of eighteen animals in the serratiopeptidase-and-antibiotic group, whereas it was present in six (37.5%) of sixteen animals in the antibiotic-only group (p = 0.001). Histological evaluation showed similar results (kappa = 0.92).

CONCLUSIONS

Serratiopeptidase was effective for eradicating infection caused by biofilm-forming bacteria in this experimental animal model. The antibiofilm property of the enzyme may enhance antibiotic efficacy in the treatment of staphylococcal infections.

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.

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.

Aortic prosthetic graft infections: radiologic manifestations and implications for management

Prosthetic graft infections are an uncommon complication of aortic bypass. These infections may have serious sequelae such as limb loss and can be lethal. They are hard to eradicate and, under certain circumstances, difficult to diagnose. Usually, computed tomography (CT) is the most efficacious imaging method for diagnosis of graft infections due to its quick availability. The sensitivity of magnetic resonance imaging in detection of perigraft infection has not been thoroughly investigated but is probably similar to that of CT. After the early postoperative period, persistent or expanding perigraft soft tissue, fluid, and gas are the CT findings of graft infection. Aortoenteric fistula should be considered a subset of aortic graft infection; however, perigraft air is more likely to be seen with an aortoenteric fistula. Other conditions associated with graft infection include pseudoaneurysm, hydronephrosis, and osteomyelitis. Adjunctive studies such as sinography, ultrasonography, gallium scanning, and labeled white blood cell scanning can be quite useful in diagnosis, determination of the extent of disease, and selection of the treatment modality. White blood cell scanning is an important complementary test to CT in ambiguous cases, such as in the early postoperative period, and may be more sensitive in detection of early graft infection.

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.

Transthoracic fistula with erosion of the ascending aorta along an IMA-protecting graft

Internal mammary artery (IMA) graft protection with nonbiodegradable material, such as polytetrafluorethylene (PTFE), is recognized as an effective means for preventing overexuberant adhesion development as well as injury of retrosternally crossing arterial grafts in the event of resternotomy and should enable better identification of the IMA graft. It is still uncertain whether the use of PTFE material is suitable for diabetic patients with complete arterial revascularization due to potential infectious complications. We report on a young diabetic patient after arterial T-grafting due to severe coronary disease and readmission with wound infection and retrosternal fistula formation 8 months after operation.