Hydroxyapatite-coated orthopaedic screws as infection resistant materials: in vitro study

Definitive Taylor Spatial Frame management for the treatment of high-energy open tibial fractures: Clinical and patient-reported outcomes

BACKGROUND

High energy open tibial fractures are complex injuries with no consensus on the optimal method of fixation. Treatment outcomes are often reported with union and re-operation rates, often without specific definitions being provided.  We sought to describe union, reoperation rates, and patient reported outcomes, using the validated EQ-VAS and Disability Rating Index (DRI) scores, following stabilisation with a Taylor Spatial Frame (TSF) and a combined orthoplastic approach for the management of soft tissues. A literature review is also provided.

METHOD

A prospective cross-sectional follow up of open tibial fractures, treated at a level 1 major trauma centre, managed with a TSF using a one ring per segment technique between January 2014 and December 2019 were identified. Demographic, injury and operative data were recorded, along with Patient Reported Outcome Measures (PROM) scores, specifically the EQ-VAS and Disability Rating Index (DRI). Union rates, defined by radiographic union scale in tibia (RUST) scores, and re-operation rates were recorded. Appropriate statistical analyses were performed, with a p<0.05 considered statistically significant.

RESULTS

Overall, 51 patients were included. Mean age was 51.2 ± 17.4 years, with a 4:1 male preponderance. Diaphyseal and distal fractures accounted for 76% of cases. Mean time in frame was 206.7 ± 149.4 days. Union was defined and was achieved in 41/51 (80.4%) patients. Deep infection occurred in 6/51 (11.8%) patients. Amputation was performed in 1 case (1.9%). Overall re-operation rate was 33%. Time to union were significantly longer if re-operation was required for any reason (uncomplicated 204±189 vs complicated 304±155 days; p = 0.0017) . EQ-VAS and DRI scores significantly deteriorated at 1 year follow-up (EQVAS 87.5 ± 11.7 vs 66.5 ± 20.4;p<0.0001 and DRI 11.9 ± 17.8 vs 39.3 ± 23.3;p<0.0001). At 1 year post op, 23/51(45.1%) required a walking aid, and 17/29 (58.6%) of those working pre-injury had returned to work.

CONCLUSION

Open tibial fracture have significant morbidity and long recovery periods as determined by EQVAS and DRI outcome measures.  We report the largest series of open tibial feature treated primarily with a TSF construct, which has similar outcomes to other techniques, and should therefore be considered as a useful technique for managing these injuries.

Role of coatings and materials of external fixation pins on the rates of pin tract infection: A systematic review and meta-analysis

BACKGROUND

Infection at the pin tract is a frequent and feared complication of external fixators (EF). The type of pin material and coatings have been regarded as possibly influencing infection rates. Over the last 20 years, few prospective clinical studies and systematic reviews addressed the role of coated pins on the rate of pin site infection in human clinical studies.

AIM

To assess the EF literature over the past 20 years on the clinical benefits of pins manufactured from varied materials and coating systems and their possible role in pin tract infection rates.

METHODS

We performed a systematic review according to the PRISMA and PICOS guidelines using four scientific platforms: PubMed, LiLacs, SciELO, and Cochrane. We searched the literature for related publications over the past 20 years.

RESULTS

A literature search yielded 29 articles, among which seven met the inclusion criteria. These studies compared stainless-steel pins and pins coated with hydroxyapatite (HA), titanium and silver. The pin tract infection definitions were arbitrary and not standardized among studies. Most studies included a low number of patients in the analysis and used a short follow-up time. Three meta-analyses were carried out, comparing stainless steel vs silver pins, stainless steel vs HA-coated pins, and titanium vs HA-coated pins. None of this analysis resulted in statistically significant differences in pin tract infection rates.

CONCLUSION

Currently, no clinical evidence supports the advantage of EF pins manufactured with materials other than stainless steel or coated over uncoated pins in reducing the rates of pin tract infections. A standardized definition of pin tract infection in external fixation is still lacking.

Ozonized Gel Against Four Candida Species: A Pilot Study and Clinical Perspectives

Ozone therapy can display a wide range of clinical beneficial effects, including antimicrobial, immune-stimulant, analgesic, anti-hypoxic actions. However, there is still a paucity of data regarding the ozone fungicide activity. Oral Candida is the most common fungal infection in the mouth among denture wearers and people with weakened immune systems. In the case of generalized candidiasis or immunocompromised patients, systemic therapy is needed, while localized infections are treated with topic medications. However, many Candida strains are resistant to antifungal drugs. The aim of this preliminary analysis is to evaluate the antimycotic efficacy of a new ozonided oil (GeliO₃), as a possible terapeutic alternative in local treatments of these infections, compared to chlorhexidine digluconate (Plak gel®). Chlorhexidine is a chemical synthesis disinfectant with a broad-spectrum antiseptic action, active against bacteria and fungi. Antimycotic activity was tested against the following four Candida species: C. albicans, C. parapsilosis, C. glabrata, C. tropicalis, through an agar diffusion method. No significant differences were found between the growth inhibition zone diameters of the ozonized gel and chlorhexidine. The results indicated that the ozonized gel may help to combat Candida infections. Moreover, useful applications could be used to counteract Candida colonization of endosseous implants.

In Vitro Re-Hardening of Bleached Enamel Using Mineralizing Pastes: Toward Preventing Bacterial Colonization

The search for materials able to remineralize human hard tissues is a modern medical challenge. In this study, the protective effect on the enamel microhardness by a paste based on hydroxyapatite and sodium fluoride (Remin Pro) was evaluated after two different enamel bleaching procedures. Forty sound human incisors were randomly assigned to different treatments: bleaching with an in-office agent (Perfect Bleach Office+); bleaching with an at-home agent (Perfect Bleach); bleaching with the in-office agent followed by the prophylaxis paste; bleaching with the at-home agent followed by the prophylaxis paste; no treatment (control). Bleaching was performed at 0, 8, 24 and 32 h, followed by a 3-min re-mineralizing treatment in the subgroups designed to receive it. Specimens underwent a micro-hardness tester and a mean Vickers Hardness number was considered for each specimen. ANOVA exhibited significant differences among groups. Post-hoc Tukey testing showed significant micro-hardness decrease after the application of both the two bleaching agents. The treatment with prophylaxis paste significantly increased the micro-hardness values of bleached enamel.

Zirconium Carboxyaminophosphonate Nanosheets as Support for Ag Nanoparticles

A layered insoluble inorganic-organic solid, namely zirconium phosphate glycine-N,N-bismethylphosphonate, was used to prepare dispersions of nanosheets to support active metals such as metallic silver nanoparticles and zinc ions. Zr phosphate-phosphonate microcrystals were first exfoliated with methylamine to produce a stable colloidal dispersion and then the methylamine was removed by treatment with hydrochloric acid. The obtained colloidal dispersion of Zr phosphate-phosphonate nanosheets was used to immobilize silver or zinc cations, via ion exchange, with the acidic protons of the sheets. The layered matrix showed a great affinity for the metal cations up taking all the added cations. The treatment of the dispersions containing silver ions with ethanol yielded metal silver nanoparticles grafted on the surface of the layered host. The samples were characterized by X-ray powder diffraction, elemental analysis transmission electron microscopy, and selected samples were submitted to antimicrobial tests. The nanocomposites based on Ag nanoparticles showed good bactericidal properties against the bacterial reference strain Staphylococcus epidermidis (S. epidermidis).

Antibacterial Properties of a Novel Zirconium Phosphate-Glycinediphosphonate Loaded with Either Zinc or Silver

A novel compound consisting of a zirconium phosphate-glycinediphosphonate (ZPGly) has recently been introduced. This 2D-structured material forming nanosheets was exfoliated under appropriate conditions, producing colloidal aqueous dispersions (ZPGly-e) which were then loaded with zinc (Zn/ZPGly) or silver ions. Silver ions were subsequently reduced to produce metallic silver nanoparticles on exfoliated ZPGly nanosheets (Ag@ZPGly). In the search for new anti-infective materials, the present study investigated the properties of colloidal dispersions of ZPGly-e, Zn/ZPGly, and Ag@ZPGly. Ag@ZPGly was found to be a bactericidal material and was assayed to define its minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) on the five most prevalent pathogens of orthopaedic implant infections, namely: Staphylococcus aureus ATCC25923, Staphylococcus epidermidis RP62A, Enterococcus faecalis ATCC29212, Escherichia coli ATCC51739, and Pseudomonas aeruginosa ATCC27853. MIC and MBC were in the range of 125–250 μg/mL and 125–1000 μg/mL, respectively, with E. coli being the most sensitive species. Even colloidal suspensions of exfoliated ZPGly nanosheets and Zn/ZPGly exhibited some intrinsic antibacterial properties, but only at greater concentrations. Unexpectedly, Zn/ZPGly was less active than ZPGly-e.

Titanium Kirschner Wires Resist Biofilms Better Than Stainless Steel and Hydroxyapatite-coated Wires: An In Vitro Study

Aim

External fixation surgery is frequently complicated by percutaneous pin site infection focused on the surface of the fixator pin. The primary aim of this study was to compare biofilm growth of clinically isolated pin site bacteria on Kirschner wires of different materials.

Materials and methods

Two commonly infecting species, Staphylococcus epidermidis and Proteus mirabilis, were isolated from patients’ pin sites. A stirred batch bioreactor was used to grow these bacteria as single culture and co-cultured biofilms on Kirschner wires made of three different materials: stainless steel, hydroxyapatite-coated steel and titanium alloy.

Results

We found that the surface density of viable cells within these biofilms was 3x higher on stainless steel and 4.5x higher on hydroxyapatite-coated wires than on the titanium wires.

Conclusion

Our results suggest that the lower rates of clinical pin site infection seen with titanium Kirschner wires are due to, at least in part, titanium’s better bacterial biofilm resistance.

Clinical significance

Our results are consistent with clinical studies which have found that pin site infection rates are reduced by the use of titanium relative to stainless steel or hydroxyapatite-coated pins.

How to cite this article

McEvoy JP, Martin P, Khaleel A, et al. Titanium Kirschner Wires Resist Biofilms Better Than Stainless Steel and Hydroxyapatite-coated Wires: An In Vitro Study. Strategies Trauma Limb Reconstr 2019;14(2):57–64.

Etiology of Implant Orthopedic Infections: A Survey on 1027 Clinical Isolates

In spite of the recent achievements derived from modern protocols of prophylaxis, orthopedic surgical infections still remain unacceptably frequent, especially in light of the often devastating outcomes of septic complications. The spectrum and the prevalence of the bacteria most frequently involved in orthopedic infections are here explored, with particular reference to those infections associated to implant biomaterials, which were grouped based on device typology. During a 30 months period (from September 2000 to April 2003), 1027 microbial strains were consecutively isolated from 699 patients undergoing revision surgery at the Rizzoli Orthopedic Institute. 775 (75.5%) of all these microorganisms were identified as belonging to the Staphylococcus genus, 82 (8%) to the Enterobacteriaceae family, 75 (7.3%) to the Pseudomonas genus, 54 (5.3%) to the Enterococcus genus and 20 (1.9%) to the Streptococcus genus. While confirming the importance of staphylococci as the most diffuse cause of infection, our data indicate an unexpectedly high prevalence of S. epidermidis on infected hip and knee arthroprostheses, respectively of 42% and 44%. The spectrum of bacteria infecting either internal or external fracture fixation devices appears to differ from that of hip and knee arthroprostheses and more closely resembles that of infections non-associated to medical devices, being characterized by a relatively higher prevalence of Staphylococcus aureus (over 40%) and Pseudomonas aeruginosa. Enterobacteriaceae and members of the Streptococcus and Corynebacterium genera are frequently associated with implants in which surgical incisions were made near the perineum, determining a completely altered spectrum.

Implant Infection and Infection Resistant Materials: A Mini Review

Implant infection is an aggressive, often irreducible post-surgical infection. It remains the primary cause of implant failure. Bacterial contamination during surgery and subsequent adhesion onto biomaterial surface of opportunistic microorganisms, such as staphylococcal species, exopolysaccharidic slimes or specific adhesins, initiates the implant infection.

Pathogenesis of periprosthestic infection is the focus of studies aimed at developing infection resistant materials.

Innate Immune Response in Implant-Associated Infections: Neutrophils against Biofilms

Biofilm has been recognized as a well-protected form of living for bacteria, contributing to bacterial pathogenicity, particularly for opportunistic species. Biofilm-associated infections are marked by their persistence. Extensive research has been devoted to the formation and composition of biofilms. The immune response against biofilms remains rather unexplored, but there is the notion that bacteria within a biofilm are protected from host defences. Here we glance at the mechanisms by which neutrophils recognize and face biofilms in implant infections and discuss the implications of this interplay, as well as speculate on its significance.

Prevention of pin site infection in external fixation: a review of the literature

Pin site infections are a common complication of external fixation that places a significant burden on the patient and healthcare system. Such infections increase the number of clinic visits required during a patient’s course of treatment, can result in the need for additional treatment including antibiotics and surgery, and most importantly can compromise patient outcomes should osteomyelitis or instability result from pin loosening or need for pin or complete construct removal. Factors that may influence the development of pin site infections include patient-specific risk factors, surgical technique, pin design characteristics, use of prophylactic antibiotics, and the post-operative pin care protocol including cleansing, dressing changes, and showering. Despite numerous studies that work to derive evidence-based recommendations for prevention of pin site infections, substantial controversy exists in regard to the optimal protocol. This review comprehensively evaluates the current literature to provide an overview of factors that may influence the incidence of pin site infections in patients undergoing treatment with external fixators, and concludes with a description of the preferred surgical and post-operative pin site protocols employed by the senior authors (ATF and SRR).

Biofilm-based implant infections in orthopaedics

The demand for joint replacement surgery is continuously increasing with rising costs for hospitals and healthcare systems. Staphylococci are the most prevalent etiological agents of orthopedic infections. After an initial adhesin-mediated implant colonization, Staphylococcus aureus and Staphylococcus epidermidis produce biofilm. Biofilm formation proceeds as a four-step process: (1) initial attachment of bacterial cells; (2) cell aggregation and accumulation in multiple cell layers; (3) biofilm maturation and (4) detachment of cells from the biofilm into a planktonic state to initiate a new cycle of biofilm formation elsewhere. The encasing of bacteria in biofilms gives rise to insuperable difficulties not only in the treatment of the infection, but also in assessing the state and the nature of the infection using traditional cultural methods. Therefore, DNA-based molecular methods have been developed to provide rapid identification of all microbial pathogens. To combat biofilm-centered implant infections, new strategies are being developed, among which anti-infective or infective-resistant materials are at the forefront. Infection-resistant materials can be based on different approaches: (i) modifying the biomaterial surface to give anti-adhesive properties, (ii) doping the material with antimicrobial substances, (iii) combining anti-adhesive and antimicrobial effects in the same coating, (iv) designing materials able to oppose biofilm formation and support bone repair.

Bacterial adhesion to poly-(D,L)lactic acid blended with vitamin E: toward gentle anti-infective biomaterials

Anti-infective properties of biomedical materials are often achieved by loading or coating them with powerful bactericides. Undesirably, these bioactive molecules can damage the host cells at the biomaterial-tissues interface and, sometimes, even determine systemic toxic effects. The search for biomaterials able to actively resist infection while displaying a safe cytocompatibility profile toward eukaryotic cells is being progressively developed. Poly-(D,L)lactic acid (PLA) is a broadly used resorbable material with established biocompatibility properties. The dissolving surfaces of a biodegradable material tend to be per se elusive for bacteria. Here, films of pristine PLA, of PLA blended with vitamin E (VitE) and PLA blended with vitamin E acetate (VitE ac) were challenged in vitro with the biofilm-producers Staphylococcus epidermidis RP62A and Staphylococcus aureus ATCC25923. The bacterial adhesion properties of the different materials were investigated on small film disc specimens by a method based on microtiter plates. Adherent bacteria were quantified by both CFU plating and bioluminescence. Significant decrease in bacterial adhesion and biofilm accumulation was found on the surface of both the enriched polymers. These findings, together with the favorable intrinsic properties of PLA and the desirable bioactivities conferred by VitE, point up the VitE-blended PLA polymers as gentle anti-infective biomaterials.

Biofilm formation on titanium implants counteracted by grafting gallium and silver ions

Biofilm-associated infections remain the leading cause of implant failure. Thanks to its established biocompatibility and biomechanical properties, titanium has become one of the most widely used materials for bone implants. Engineered surface modifications of titanium able to thwart biofilm formation while endowing a safe anchorage to eukaryotic cells are being progressively developed. Here surfaces of disks of commercial grade 2 titanium for bone implant were grafted with gallium and silver ions by anodic spark deposition. Scanning electron microscopy of the surface morphology and energy dispersive X-ray spectroscopy were used for characterization. Gallium-grafted titanium was evaluated in comparison with silver-grafted titanium for both in vivo and in vitro antibiofilm properties and for in vitro compatibility with human primary gingival fibroblasts. Surface-modified materials showed: (i) homogeneous porous morphology, with pores of micrometric size; (ii) absence of cytotoxic effects; (iii) ability to support in vitro the adhesion and spreading of gingival fibroblasts; and (iv) antibiofilm properties. Although both silver and gallium exhibited in vitro strong antibacterial properties, in vivo gallium was significantly more effective than silver in reducing number and viability of biofilm bacteria colonies. Gallium-based treatments represent promising titanium antibiofilm coatings to develop new bone implantable devices for oral, maxillofacial, and orthopedic applications.

The interaction of bacteria with engineered nanostructured polymeric materials: a review

Bacterial infections are a leading cause of morbidity and mortality worldwide. In spite of great advances in biomaterials research and development, a significant proportion of medical devices undergo bacterial colonization and become the target of an implant-related infection. We present a review of the two major classes of antibacterial nanostructured materials: polymeric nanocomposites and surface-engineered materials. The paper describes antibacterial effects due to the induced material properties, along with the principles of bacterial adhesion and the biofilm formation process. Methods for antimicrobial modifications of polymers using a nanocomposite approach as well as surface modification procedures are surveyed and discussed, followed by a concise examination of techniques used in estimating bacteria/material interactions. Finally, we present an outline of future sceneries and perspectives on antibacterial applications of nanostructured materials to resist or counteract implant infections.

Cytocompatibility and antibacterial properties of capping materials

The aim of this study was to evaluate and compare the antimicrobial activity and cytocompatibility of six different pulp-capping materials: Dycal (Dentsply), Calcicur (Voco), Calcimol LC (Voco), TheraCal LC (Bisco), MTA Angelus (Angelus), and Biodentine (Septodont). To evaluate antimicrobial activity, materials were challenged in vitro with Streptococcus mutans, Streptococcus salivarius, and Streptococcus sanguis in the agar disc diffusion test. Cytocompatibility of the assayed materials towards rat MDPC-23 cells was evaluated at different times by both MTT and apoptosis assays. Results significantly differed among the different materials tested. Both bacterial growth inhibition halos and cytocompatibility performances were significantly different among materials with different composition. MTA-based products showed lower cytotoxicity and valuable antibacterial activity, different from calcium hydroxide-based materials, which exhibited not only higher antibacterial activity but also higher cytotoxicity.

Prevention of infection in external fixator pin sites

Infection in external fixator pins is known to be a significant problem, with incidences between 3% and 80% reported in the literature. An infection occurs when planktonic bacteria adhere to external fixator pins and subsequently produce a biofilm which protects the bacteria from host defences. The most commonly implicated organisms are Staphylococcus aureus and Staphylococcus epidermidis. Once an infection occurs, treatment is difficult. Systemic antibiotics have limited benefits and considerable side-effects. The only definitive management is removal of the pin. This review will consider the current and potential future strategies for reducing pin site infection. Techniques to prevent infection must prevent bacterial adhesion, allow good osteointegration and have a low toxicity. Current areas of interest reviewed are titanium-copper alloys, nanosilver coatings, nitric oxide coatings, chitosan coatings, chlorhexidine and iodine, hydroxyapatite and antibiotic coatings. At present there is no consensus on the prevention of pin site infection, and there is a paucity of randomized controlled trials on which to draw a conclusion. Whilst a number of these strategies have potential future use, many of the above strategies need further studies in animal models to ensure no cytotoxicity and prevention of osteointegration. Following this, well-designed randomized controlled clinical trials are required to give future ways to prevent external fixator pin site infections.

Hydroxyapatite-coated external fixation pins

The aim of this review is to report on studies of hydroxyapatite-coated external fixation pins as a solution to enhance pin fixation. In a highly loaded animal study, three tapered pin types were compared: Type A uncoated, Type B coated with hydroxyapatite and Type C coated with titanium. There was a 13-fold increase in the extraction torque of Type B pins compared with Type A, and a twofold increase compared with Type C pins. Extraction torque was significantly lower compared with the corresponding insertion torque in both Types A (p < 0.001) and C (p = 0.003). Conversely, with the hydroxyapatite-coated pins there was no difference between extraction and insertion torque. In a clinical study of 76 external fixation pins in 19 patients treated with hemicallotasis for osteoarthritis on the medial side of the knee, pin insertion and extraction torque forces were measured. The patients were randomized to be treated with either standard tapered pins or tapered pins coated with hydroxyapatite. Extraction torque of the hydroxyapatite-coated pins was higher than the extraction torque of the standard pins in both cancellous and cortical bone (p < 0.005). In a prospective, randomized clinical study of osteoporotic wrist fractures, extraction torque of the coated pins was higher than with standard pins (p < 0.0001). These studies demonstrate that with the use of hydroxyapatite-coated pins, no deterioration of pin fixation occurs, and that there is no significant pin loosening and infection, regardless of bone type and loading conditions.

Immobilized antibiotics to prevent orthopaedic implant infections

Many surgical procedures require the placement of an inert or tissue-derived implant deep within the body cavity. While the majority of these implants do not become colonized by bacteria, a small percentage develops a biofilm layer that harbors invasive microorganisms. In orthopaedic surgery, unresolved periprosthetic infections can lead to implant loosening, arthrodeses, amputations and sometimes death. The focus of this review is to describe development of an implant in which an antibiotic tethered to the metal surface is used to prevent bacterial colonization and biofilm formation. Building on well-established chemical syntheses, studies show that antibiotics can be linked to titanium through a self-assembled monolayer of siloxy amines. The stable metal-antibiotic construct resists bacterial colonization and biofilm formation while remaining amenable to osteoblastic cell adhesion and maturation. In an animal model, the antibiotic modified implant resists challenges by bacteria that are commonly present in periprosthetic infections. While the long-term efficacy and stability is still to be established, ongoing studies support the view that this novel type of bioactive surface has a real potential to mitigate or prevent the devastating consequences of orthopaedic infection.

Biofilm formation in Staphylococcus implant infections. A review of molecular mechanisms and implications for biofilm-resistant materials

Implant infections in orthopaedics, as well as in many other medical fields, are chiefly caused by staphylococci. The ability of growing within a biofilm enhances the chances of staphylococci to protect themselves from host defences, antibiotic therapies, and biocides. Advances in scientific knowledge on structural molecules (exopolysaccharide, proteins, teichoic acids, and the most recently described extracellular DNA), on the synthesis and genetics of staphylococcal biofilms, and on the complex network of signal factors that intervene in their control are here presented, also reporting on the emerging strategies to disrupt or inhibit them. The attitude of polymorphonuclear neutrophils and macrophages to infiltrate and phagocytise biofilms, as well as the ambiguous behaviour exhibited by these innate immune cells in biofilm-related implant infections, are here discussed. Research on anti-biofilm biomaterials is focused, reviewing materials loaded with antibacterial substances, or coated with anti-adhesive/anti-bacterial immobilized agents, or surfaced with nanostructures. Latter approaches appear promising, since they avoid the spread of antibacterial substances in the neighbouring tissues with the consequent risk of inducing bacterial resistance.

Internalization by osteoblasts of two Staphylococcus aureus clinical isolates differing in their adhesin gene pattern

Staphylococcus aureus is the leading etiologic agent of implant orthopedic infections. Until recently S. aureus was considered a mere extracellular pathogen; it then turned out to be able to invade eukaryotic cells. Adhesion of S. aureus to peri-prosthesis tissues represents the starting of the infection pathogenesis and the first step of the subsequent internalization of S. aureus by host cells. In the present work the experimental observations on two epidemic clinical strains differing in their adhesin pattern demonstrate the crucial role of the fibronectin-binding protein A in the internalization process and suggest that CNA and Bbp adhesins can play a synergistic role by acting in the initial adhesion of S. aureus to osteoblasts, thus favoring the subsequent FnBPA-mediated internalization.

Concise Survey of Staphylococcus Aureus Virulence Factors that Promote Adhesion and Damage to Peri-Implant Tissues

Staphylococcus aureus is the leading cause of infection in orthopedic implants and of osteomyelitis consequent to it. Here we focus on the wide array of virulence factors that endow S. aureus with its abilities to colonize peri-prosthesis tissues and to attack and damage them. Following an infective strategy orchestrated by agr locus, Staphylococcus aureus first deploys virulence factors for adhesion to the prosthesis and peri-prosthesis tissues and then launches its attack by delivering destructive factors.

Extracellular DNA in Biofilms

Extracellular DNA (eDNA) is an important biofilm component that was recently discovered. Its presence has been initially observed in biofilms of Pseudomonas aeruginosa, Streptococcus intermedius, Streptococcus mutans, then Enterococcus faecalis and staphylococci. Autolysis is the common mechanism by which eDNA is released. In P. aeruginosa eDNA is generated by lysis of a bacterial subpopulation, under control of quorum sensing system. In E. faecalis autolysis proceeds in a fratricide mode, resulting from a process similar to necrosis of eukaryotic cells. In Staphylococcus aureus autolysis originates by an altruistic suicide, i.e., a programmed cell death similar to apoptosis of eukaryotic cells. In S. aureus autolysis is mediated by murein hydrolase, while in S. epidermidis by the autolysin protein AtlE. In P. aeruginosa eDNA is located primarily in the stalks of mushroom-shaped multicellular structures. In S. aureus the crucial role of eDNA in stabilizing biofilm is highlighted by the disgregating effect of DNase I. eDNA represents an important mechanism for horizontal gene transfer in bacteria. eDNA and other microbial structural motifs are recognized by the innate immune system via the TLR family of pattern recognition receptors (PRRs).

Exopolysaccharide Production by Staphylococcus Epidermidis and its Relationship with Biofilm Extracellular DNA

Implant-related infections are difficult to treat because they are very often associated with biofilm-forming micro-organisms capable of resisting host immune defenses and surviving conventional antibiotic treatments. In Staphylococcus epidermidis biofilm-forming strains, the polysaccharide intercellular adhesin (PIA), whose expression is encoded by the icaADBC operon, is recognized as a main staphylococcal accumulation mechanism. Nevertheless, various observations have shown that PIA expression is dispensable and a variety of additional/alternative accumulation mechanisms, including extracellular DNA (eDNA) and several other factors of proteic nature, can compensate for icaADBC low expression or even for its absence. A suggestive hypothesis points to the possibility that changes in biofilm extracellular matrix composition can be induced in different environmental niches. In this study we aimed at investigating the relationship between the exopolysaccharide and eDNA biofilm components, screening 55 S. epidermidis clinical isolates by means of a simple fluorescence-based microtiter-plate assay. Our findings indicate the existence of a certain degree of correlation, although not a strict one, between eDNA and the exopolysaccharide component. The presence of exopolysaccharide greatly varied even in strains belonging to the same strain type determined by automated riboprinting.

Emerging Pathogenetic Mechanisms of the Implant-Related Osteomyelitis by Staphylococcus Aureus

Implant-related osteomyelitis is a severe and deep infection of bone that arises and develops all around an implant. Staphylococcus aureus is the first cause of osteomyelitis, whether implant-related or not. Bone is an optimal substratum for S. aureus, since this bacterium expresses various adhesins by which can adhere to bone proteins and to the biomaterial surfaces coated with the proteins of the host extracellular matrix. S. aureus is able not only to colonize bone tissues, but also to invade and disrupt them by entering bone cells and inducing cell death and osteolysis. Here we illustrate the pathogenetic mechanisms that can explain how the osteomyelitis sets in and develops around an implant.

New Trends in Diagnosis and Control Strategies for Implant Infections

In implant infections, a quick and reliable identification of the etiological agent is crucial to realizing efficacious therapies. Among molecular methods, automated ribotyping has proven to be an accurate and rapid technique. More recently, MALDI-TOF/MS and PCR-electrospray ionization (ESI)/ MS have been applied successfully to microbiological diagnosis. In implant infections, biofilm is still the major problem for bacterial persistence and recalcitrance to antibiotic therapy. Among biofilm-disrupting agents, enzymes promise the greatest therapeutic possibilities. DNase I degrades biofilm extracellular DNA and has been shown to sensitize biofilm to various biocides and anionic detergents, while dispersin B acts on biofilm exopolysaccharide and, combined with antiseptic, gives a broad-spectrum antibiofilm and antimicrobial activity. The novel antimicrobial approach based on photodynamic treatment (PDT) applies, in combination with antibiotics, to the implant or medical devices reachable by optical fibers. Better progress could be gained by the development of infection-resistant biomaterials able to both inhibit bacterial adhesion and promote tissue integration. New knowledge regarding the fibronectin-mediated internalization of Staphylococcus aureus by osteoblasts, and on its role in the pathogenesis of implant-related osteomyelitis, paves the way for the development of vaccines against staphylococcal adhesins, to prevent both adhesion on biomaterials and bacterial invasion of bone cells.

Nanotextured titanium surfaces for enhancing skin growth on transcutaneous osseointegrated devices

A major problem with transcutaneous osseointegrated implants is infection, mainly due to improper closure of the implant-skin interface. Therefore, the design of transcutaneous osseointegrated devices that better promote skin growth around these exit sites needs to be examined and, if successful, would clearly limit infection. Due to the success already demonstrated for orthopedic implants, developing surfaces with biologically inspired nanometer features is a design criterion that needs to be investigated for transcutaneous devices. This study therefore examined the influence of nanotextured titanium (Ti) created through electron beam evaporation and anodization on keratinocyte (skin-forming cell) function. Electron beam evaporation created Ti surfaces with nanometer features while anodization created Ti surfaces with nanotubes. Conventional Ti surfaces were largely micron rough, with few nanometer surface features. Results revealed increased keratinocyte adhesion in addition to increased keratinocyte spreading and differences in keratinocyte filopodia extension on the nanotextured Ti surfaces prepared by either electron beam evaporation or anodization compared to their conventional, unmodified counterparts after 4h. Results further revealed increased keratinocyte proliferation and cell spreading over 3 and 5days only on the nanorough Ti surfaces prepared by electron beam evaporation compared to both the anodized nanotubular and unmodified Ti surfaces. Therefore, the results from this in vitro study provided the first evidence that nano-modification techniques should be further researched as a means to possibly improve skin growth, thereby improving transcutaneous osseointegrated orthopedic implant longevity.

Covalent coating of hydroxyapatite by keratin stabilizes gentamicin release

A novel hybrid hydroxyapatite (HAP) matrix, covalently coated with rarely applied, hardly degradable keratin and effectively modified by gentamicin immobilized in mixed-type mode (via interactions of diverse strength), was created. This hybrid showed a remarkably high drug immobilization yield and the most sustainable antibiotic release among all tested composites. It was also able to inhibit bacterial growth, both in surrounding liquid and on matrix surface, much longer (for at least 121 days of experiment) than analogous gelatin-modified and nonmodified matrices. Gentamicin-keratin-coated-HAP granules were nontoxic to human osteoblasts and enabled their proliferation with a rate similar as noncoated HAP. Presence of keratin on HAP granules seemed to slightly enhance the osteoblast proliferation. The results indicate that newly created HAP hybrid with covalently immobilized keratin and gentamicin--nontoxic and osteoblast-friendly--is a promising biomaterial of significantly prolonged antibacterial activity.

Effect of hydroxyapatite coating and polymethylmethacrylate on stainless steel implant-site infection with Staphylococcus epidermidis in a sheep model

We aimed to study the influence of hydroxyapatite (HA) coating and polymethylmethacrylate (PMMA) cement on the risk of development of stainless steel implant-site infection with Staphylococcus epidermidis in a sheep model. Uncoated, HA-coated, and PMMA-cemented stainless steel implants were inserted in the left femur of 30 sheep. For each type of implant, sheep were inoculated with S. epidermidis in the intramedullary canal and one non-inoculated group was used as control. After 6 weeks, infection was evaluated using clinical, radiological, bacteriological, and histological criteria. Radiological and clinical results were normal. Cultures were negative in the control sheep. In the inoculated sheep, interposition tissue and bone cultures were positive in 2 of 6 uncoated, 6 of 6 HA, and 6 of 6 PMMA implants with a mean bacteria count of 5.2 +/- 1.17, 3.5 +/- 0.7, and 3.9 +/- 0.9 log10 cfu/g, respectively (NS), for interposition tissue, and 4 +/- 0.01, 2.9 +/- 0.6, and 2.5 +/- 1.3 log10 cfu/g, respectively (NS) for bone. The polymorphonuclear leukocyte (PMN) score (mean number of PMN per 10 different microscopic high-power fields >or=5) in interposition tissue was >or=3 in 6 of 6 HA, significantly different from uncoated (3 of 6) and PMMA (2 of 6) groups (p = 0.04). The HA and PMMA inoculated groups had a higher infection rate than the uncoated inoculated group (p = 0.06). In this experimental sheep model of S. epidermidis infection at the bone-biomaterial interface, HA seems to be at higher risk of infection compared with uncoated or PMMA-cemented stainless steel, when inoculation is intramedullary and contemporary with implantation.

In vivo effects of coating loaded and unloaded Ti implants with collagen, chondroitin sulfate, and hydroxyapatite in the sheep tibia

The in vivo effects of coating titanium implants with organic extracellular matrix molecules were examined in the sheep tibia. Titanium screws (5.0 mm) were coated with type I collagen (Ti/Coll) or type I collagen and chondroitin sulfate (Ti/Coll/CS) by biomimetic fibrillogenesis. Uncoated screws (Ti) and screws coated with hydroxyapatite (Ti/HA) served as control. Six adult female sheep received one screw of each type to stabilize a midshaft tibial fracture with external fixation. Four cylindrical implants of 4-mm outer diameter and 3.3-mm inner diameter with the same coatings were inserted into the tibial head. No pin track infections were seen at the time of implant retrieval 6 weeks after implantation. Extraction torque was greater for Ti/HA (1181 Nmm) and Ti/Coll/CS (1088 Nmm) compared to Ti/Coll (900 Nmm) and Ti (904 Nmm) [N.S.]. Newly formed bone was noted around all coated screws within the medullary cavity. Macrophage and osteoclast activity was significantly reduced around Ti/Coll/CS in both types of implants compared to uncoated controls (p < 0.05). Osteoblast activity was significantly increased around loaded Ti/Coll and Ti/Coll/CS screws compared to uncoated Ti screws (p < 0.05). Microtomographic evaluation (SRmicroCT) revealed no significant differences in new bone formation around the unloaded tibial head implants. Coating of external fixation devices with of type I collagen and chondroitin sulfate appears to have similar effects with respect to stability and bone healing as HA but with less osteoclast activity. These findings were more pronounced under loaded than unloaded conditions in the sheeptibia.

External Circular Fixation: A Comparison of Infection Rates Between Wires and Conical Half-Pins with Threads Outside or Inside the Skin

BACKGROUND

The purpose of this study was to evaluate if there is a difference in the rates of infection between Ilizarov wires and half-pins and between half-pins with threads outside and inside the skin in circular fixators modified by Catagni and Cattaneo.

METHODS

Between May and December 2004, 218 patients with circular Ilizarov fixators for various orthopaedic indications who visited our Ilizarov clinic were subjected to a one-time evaluation of half-pins and wires.

RESULTS

A total of 1,093 half-pins were checked and 34 (3.11%) of these were infected (50% with threads outside and 50% with threads inside the skin). Among a total number of 951 wires (1,092 pin tracts) checked, 45 (4.73%) were infected.

CONCLUSIONS

We conclude that the circular Ilizarov fixation with conical half-pins and wires has similar rate of infection compared with conventional Ilizarov circular fixator. Moreover, there is no difference in infection rates between pins with threads inside the skin as compared to those with threads outside the skin.

An investigation of the effects of hydroxyapatite coatings on the fixation strength of cortical screws

Hydroxyapatite (HA) are commonly applied to orthopaedic implants for acceleration of osteointegration and so overcoming the loosening problems such as in cortical screws. Electrophoretic deposition (EPD) of hydroxyapatite was applied for coating of cortical screws in this work. The effects of hydroxyapatite-coated and uncoated cortical screws on insertion and extraction torque were investigated through in vivo experiments. Three groups of screws were undertaken: first group with no coating, second group coated with HA and the third group coated with HA+interlayer, a synthetic calcium silicate compound. Five sheep were operated, and 60 cortical (20 x 3) screws from those of groups were implanted in cortical femurs to observe the effect of HA and interlayer on screws. Results show that as an alternative to plasma spray coating method, the EPD process enables to produce a quick, easy, cheap and uniform adjustable coating layer. Also from biomechanical and SEM examinations, HA coating by EPD method of cortical screws resulted in extremely improved fixation with reduced risk of loosening problem.

Evaluation of bacterial adhesion of Streptococcus mutans on dental restorative materials

Bacterial adhesion to the surface of composite resins and other dental restorative materials is an important parameter in the aetiology of secondary caries formation. The aim of the present study was to investigate the adhesion of a Streptococcus mutans strain (ATCC 25175) on the surface of different restorative materials. The test materials examined included three flowable composites (Filtek Flow, Tetric Flow, and Arabesk Flow), three microhybrid composites (Clearfil APX, Solitaire 2, and Z250), two glass-ionomers (Fuji IX, Fuji IX fast), a compomer (F2000), an ormocer (Admira), and a control reference material (tissue culture grade, surface treated polystyrene). The adhesion tests were carried out in 24-well plates. Quantitative turbidimetric measurements were finally performed in order to indirectly evaluate the amount of bacteria retained on the material surface after in vitro exposure to the bacteria suspension. Under these conditions, with the exception of the Admira ormocer and the Fuji IX fast glass ionomer, which were found to be more adhesive, all the other material surfaces showed a similar susceptibility to bacterial adhesion, exhibiting values not significantly different than the reference polystyrene control. Furthermore, the release of fluoride from some of the test surfaces did not appear capable to reduce early bacterial adhesion.

Effect of spark plasma sintering on the microstructure and in vitro behavior of plasma sprayed HA coatings

The crystalline phases and degree of crystallinity in plasma sprayed calcium phosphate coatings on Ti substrates are crucial factors that influence the biological interactions of the materials in vivo. In this study, plasma sprayed hydroxyapatite (HA) coatings underwent post-spray treatment by the spark plasma sintering (SPS) technique at 500 degrees C, 600 degrees C, and 700 degrees C for duration of 5 and 30 min. The activity of the HA coatings before and after SPS are evaluated in vitro in a simulated body fluid. The surface microstructure, crystallinity, and phase composition of each coating is characterized by scanning electron microscopy and X-ray diffractometry before, and after in vitro incubation. Results show that the plasma sprayed coatings treated for 5 min in SPS demonstrated increased proportion of beta-TCP phase with a preferred-orientation in the (214) plane, and the content of beta-TCP phase corresponded to SPS temperature, up to 700 degrees C. SPS treatment at 700 degrees C for 30 min enhanced the HA content in the plasma spray coating as well. The HA coatings treated in SPS for 5 min revealed rapid surface morphological changes during in vitro incubation (up to 12 days), indicating that the surface activity is enhanced by the SPS treatment. The thickest apatite layer was found in the coating treated by SPS at 700 degrees C for 5 min.

In vitro corrosion behavior of bioceramic, metallic, and bioceramic-metallic coated stainless steel dental implants

OBJECTIVES

The most common metals and alloys used in dentistry may be exposed to a process of corrosion in vivo that make them cytotoxic. The biocompatibility of dental alloys is primarily related to their corrosion behavior. The aim of this work was to evaluate the corrosion behavior and thus the biocompatibility of the uncoated and coated stainless steels and compare the effect of type of coatings on corrosion behavior.

METHODS

Three types of coatings, hydroxyapatite (HA), titanium (Ti), and a double-layer HA/Ti on AISI 316L stainless steel were made. HA coating was produced using plasma-spraying technique and Ti coating was made using physical vapor deposition process. In order to perform a novel double-layer composite coating, a top layer of HA was plasma-sprayed over a physical vapor deposited Ti layer on AISI 316L stainless steel. Structural characterization techniques including XRD, SEM and EDX were used to investigate the microstructure, morphology and crystallinity of the coatings. Electrochemical potentiodynamic tests were performed in physiological solutions in order to determine and compare the corrosion behavior of the coated and uncoated specimens as an indication of biocompatibility.

RESULTS

Double-layer HA/Ti coating on AISI 316L SS had a positive effect on improvement of corrosion behavior. The decrease in corrosion current densities was significant for these coated specimens and was much lower than the values obtained for uncoated and single HA coated specimens. Ti coating on AISI 316L SS also has a beneficial effect on corrosion behavior. The results were compared with the results of corrosion behavior of HA coated commercially pure titanium (cpTi) and uncoated cpTi.

SIGNIFICANCE

These results demonstrated that the double-layer HA/Ti coated 316L SS can be used as an endodontic implant and two goals including improvement of corrosion resistance and bone osteointegration can be obtained simultaneously.

[Tensile strength of bone fixation of hydroxyapatite coated Schanz screws of the Heidelberg External Fixation System (HEFS)--comparative torque measurements in clinical use and in cadaver tibia]

It is claimed in the literature that hydroxyapatite(HA)-coated screws of external fixators have superior fixation strength in bone, which is postulated to lead to a substantial decrease in loosening and infection rates. We report on a study of the maximum torque values developed while inserting and removing 30 HA-coated Schanz screws of 8 Heidelberg external fixation systems applied to the tibia to correct leg length differences and axial deformities. The infection rate was determined in accordance with defined criteria, and was found to be about 20% for the HA-coated screws. Screws without infection showed an extraction torque above insertion torque, screws with infection an extraction torque below. A significant correlation (p = 0.05) was seen between infection and decrease in fixation strength (quotient: loosening torque/tightening torque). To exclude the impact of such biological processes as osteointegration and bone remodelling, the clinical results were compared with the torques measured for coated and uncoated Schanz screws in a human cadaveric tibia. A significantly higher fixation strength in bone was found for HA-coated screws in comparison with uncoated screws (p = 0.002). These data warrant a clinical study directly comparing HA-coated and uncoated Schanz screws.

In vitro and in vivo biocompatibility testing of Ti-6Al-7Nb alloy with and without plasma-sprayed hydroxyapatite coating

The Ti-6Al-7Nb alloy has been recently developed for biomedical use, particularly for orthopedics and dental applications. Osteosynthesis has been used to analyze biocompatibility and osseoconduction properties. The interaction of the implant with its biological environment, the formation of the implant material/tissue interface, and the long-term success or failure of integration in the human body is strongly connected with the surface properties of the implant device. This study was undertaken to evaluate the processes involved in biological responses of the Ti-6Al-7Nb alloy with and without hydroxyapatite coatings with both in vitro and in vivo tests. The results were analyzed by scanning electron microscopy (SEM) and energy-dispersive x-ray (EDX) microanalysis. The morphology of the in vitro and in vivo testing results with hydroxyapatite coating was similar to those obtained on the uncoated samples. A mineralized extracellular matrix was formed on all materials. Observation of the interface between the cell layer and substrata showed the presence of calcium and phosphorous-rich globular deposits associated with collagen fibers on all materials in vitro and in vivo. A higher density of these globular deposits was observed in all samples.

In catheter infections by Staphylococcus epidermidis the intercellular adhesion (ica) locus is a molecular marker of the virulent slime-producing strains

Recently, it has been shown that S. epidermidis includes the ica operon responsible for slime production. In the operon, coexpression of icaA and icaD genes is required for full slime synthesis. In this study, the presence of icaA and icaD genes was searched for in a collection of 100 Staphylococcus epidermidis strains from catheter-associated infections by an original PCR method. Another 51 strains of S. epidermidis isolated from the skin or mucosa of healthy volunteers (26 of which derived from the hospital staff) were also investigated. Slime-forming ability was phenotypically tested on Congo red agar plates. Sixty-one percent of the strains isolated from catheters were icaA- icaD-positive and produced slime. The results indicate that detection of ica genes by a PCR method is a useful tool for prompt identification of S. epidermidis slime-forming strains isolated from catheter-related infections. Also, three saprophytic strains from the hospital staff were positive for slime synthesis and presence of ica genes, suggesting a potential diffusion of slime-forming strains in hospital personnel.

State of the art review: techniques to avoid pin loosening and infection in external fixation

The purpose of this manuscript is to review techniques of optimizing the interface between the bone and pin in external fixation to minimize pin loosening and infection.

CONCLUSIONS

Among the different techniques to improve the bone-pin interface in external fixation, coating the pins with hydroxyapatite proved to be the most effective. In a highly loaded animal study, three pin types were compared. Type A remained uncoated, type B was coated with hydroxyapatite, and Type C was coated with titanium. Radiographic rarefaction of the bone pin tract was lower in type B pins. Extraction torque was thirteen times higher in type B pins compared to type A and two times higher compared to type C pins. Extraction torque was significantly lower compared to the corresponding insertion torque in both types A and C. In contrast, in the hydroxyapatite coated pins there was no difference between extraction and insertion torque. At sixty times magnification, bone pin contact of type B and C pins was significantly higher than type A. At 10,000 times magnification direct bone pin contact was found only in type B pins. In a clinical study the pin insertion and extraction torque forces were measured in a study of seventy-six external fixation pins in nineteen patients treated with hemicallotasis for osteoarthritis of the medial side of the knee. The patients were randomized to be treated with either standard tapered pins or tapered pins coated with hydroxyapatite. Extraction torque of the hydroxyapatite coated pins was higher than the standard ones in both cancellous and cortical bone. These studies show that in hydroxyapatite coated pins there is no deterioration of the bone-pin interface strength and there is optimal bone-pin contact. Among the various pin types coated with hydroxyapatite, the best results were obtained with the tapered pins.

Presence of icaA and icaD genes and slime production in a collection of staphylococcal strains from catheter-associated infections

Both Staphylococcus epidermidis and Staphylococcus aureus are important causes of infections associated with catheters and other medical devices. It has recently been shown that not only S. epidermidis but also S. aureus can produce slime and carries the ica operon responsible for slime production. In the operon, coexpression of icaA and icaD is required for full slime synthesis. In this study, the presence of icaA and icaD was determined in a collection of 91 staphylococcal (68 S. epidermidis and 23 S. aureus) strains from intravenous catheter-associated infections, in 10 strains from the skin and mucosa of healthy volunteers, and in two reference strains by a PCR method. Slime-forming ability was tested on Congo red agar plates; 49% of S. epidermidis strains from catheters and, surprisingly, 61% of S. aureus strains were icaA and icaD positive and slime forming. All the saprophytic strains turned out to be negative for both icaA and icaD and also non-slime forming. Two S. aureus and one S. epidermidis strain from catheters, detected as icaA and icaD positive by PCR analysis and as slime forming (black colonies) at 24 h on Congo red agar, at 48 h exhibited tiny red spikes at the center of black colonies. The onset of these variants could not be ascribed to a mutagenic potential of Congo red, which, in the Ames test, was devoid of mutagenicity. PCR analysis showed that these red variants were negative for both icaA and icaD and even lacking the entire icaADBC operon. The data reported indicate an important role of ica genes as a virulence marker in staphylococcal infections from intravenous catheters.

In vitro study of blood-contacting properties and effect on bacterial adhesion of a polymeric surface with immobilized heparin and sulphated hyaluronic acid

The blood-contacting properties and the effect on bacterial adhesion of a material based on polyurethane and poly(amido-amine) (PUPA), both in its native form and with the anticoagulant molecules heparin or sulphated hyaluronic acid (HyalS3.5) electrostatically bonded to its surface, were evaluated and compared in vitro. The presence of the biological molecules on the surface was revealed by a dye test and ATR/FTIR analysis. Bound heparin was found to maintain its physiological action, in terms of thrombin inactivation, as well as did free heparin. Moreover, it reduced the degree of platelet adhesion. On the contrary, bound HyalS3.5 lost its anticoagulant activity, though it reduced platelet adhesion. The number of platelets on both modified surfaces was low. Their shape distribution, as determined by SEM, did not differ significantly on the two modified surfaces or with respect to the bare PUPA surface. HyalS3.5 and heparin also inhibited adhesion of Staphylococcus epidermidis to the material. A possible relationship between the platelet and bacterial adhesion is ascribed to the mediating role of plasma proteins.

A rapid PCR method for the detection of slime-producing strains of Staphylococcus epidermidis and S. aureus in periprosthesis infections

In periprosthesis tissues, Staphylococcus epidermidis produces extracellular polysaccharide slime. Recently it has been shown that S. aureus also produces slime and that both S. epidermidis and S. aureus contain the ica operon responsible for slime production. In the operon, icaA encodes for N-acetylglutaminyltransferase, the enzyme for polysaccharide synthesis. However, co-expression of icaA and icaD is required for full slime synthesis. The slime-producing strains of both S. epidermidis and S. aureus are more virulent and are responsible for severe postsurgical or periprosthesis infections. The authors describe a simple, rapid, and reliable polymerase chain reaction method to detect icaA and icaD. The method was applied to the detection of ica genes on two reference strains, 15 strains each of S. epidermidis and S. aureus from periprosthesis infections and 10 strains from the skin and mucosa of healthy volunteers. icaA and icaD were detectable only in slime-producing strains (tested for slime production on Congo Red agar), and never in nonslime-producing ones. This method is a straightforward way of detecting the slime-producing ability by S. epidermidis and S. aureus. In clinical specimens this polymerase chain reaction method enables rapid diagnosis of virulent slime-producing strains with respect to the traditional culture method on Congo Red agar, which requires much more time. Rapid identification of the virulent properties of the bacterial strain responsible for a staphylococcal infection is crucial for deciding treatment.