Peri-prosthetic infections are notoriously difficult to treat as the biomaterial implant is ideal for bacterial adhesion and biofilm formation, resulting in decreased antibiotic sensitivity. Previously, we reported that vancomycin covalently attached to a Ti alloy surface (Vanc-Ti) could prevent bacterial colonization. Herein we examine the effect of this Vanc-Ti surface on Staphylococci epidermidis, a Gram-positive organism prevalent in orthopaedic infections. By direct colony counting and fluorescent visualization of live bacteria, S. epidermidis colonization was significantly inhibited on Vanc-Ti implants. In contrast, the gram-negative organism Escherichia coli readily colonized the Vanc-Ti rod, suggesting retention of antibiotic specificity. By histochemical and SEM analysis, Vanc-Ti prevented S. epidermidis biofilm formation, even in the presence of serum. Furthermore, when challenged multiple times with S. epidermidis, Vanc-Ti rods resisted bacterial colonization. Finally, when S. epidermidis was continuously cultured in the presence of Vanc-Ti, the bacteria maintained a Vanc sensitivity equivalent to the parent strain. These findings indicate that antibiotic derivatization of implants can result in a surface that can resist bacterial colonization. This technology holds great promise for the prevention and treatment of periprosthetic infections. b s t r a c tPeri-prosthetic infections are notoriously difficult to treat as the biomaterial implant is ideal for bacterial adhesion and biofilm formation, resulting in decreased antibiotic sensitivity. Previously, we reported that vancomycin covalently attached to a Ti alloy surface (Vanc-Ti) could prevent bacterial colonization. Herein we examine the effect of this Vanc-Ti surface on Staphylococci epidermidis, a Gram-positive organism prevalent in orthopaedic infections. By direct colony counting and fluorescent visualization of live bacteria, S. epidermidis colonization was significantly inhibited on Vanc-Ti implants. In contrast, the gram-negative organism Escherichia coli readily colonized the Vanc-Ti rod, suggesting retention of antibiotic specificity. By histochemical and SEM analysis, Vanc-Ti prevented S. epidermidis biofilm formation, even in the presence of serum. Furthermore, when challenged multiple times with S. epidermidis, Vanc-Ti rods resisted bacterial colonization. Finally, when S. epidermidis was continuously cultured in the presence of Vanc-Ti, the bacteria maintained a Vanc sensitivity equivalent to the parent strain. These findings indicate that antibiotic derivatization of implants can result in a surface that can resist bacterial colonization. This technology holds great promise for the prevention and treatment of periprosthetic infections.

The simple colorimetric strip test that detects the presence of leukocyte esterase in synovial fluid appears to be an extremely valuable addition to the physician's armamentarium for the diagnosis of periprosthetic joint infection. The leukocyte esterase reagent strip has the advantages of providing real-time results, being simple and inexpensive, and having the ability to both rule out and confirm periprosthetic joint infection. However, additional multicenter studies are required to substantiate the results of our preliminary investigation before the reagent strip can be used confidently in the clinic or intraoperative setting.

Periprosthetic infections are life-threatening complications that occur in about 6% of medical device insertions. Stringent sterile techniques have reduced the incidence of infections, but many implant patients are at high risk for infection, especially the elderly, diabetic, and immune compromised. Moreover, because of low vascularity at the site of the new implant, antibiotic prophylaxis is often not effective. To address this problem, we designed a covalent modification to titanium implant surfaces to render them bactericidal. Specifically, we aminopropylated titanium, a widely used implant material and extended a tether by solid phase coupling of ethylene glycol linkers, followed by solid phase coupling of vancomycin. Vancomycin covalently attached to titanium still bound soluble bacterial peptidoglycan, reduced Staphylococcus aureus colony-forming units by 88% +/- 16% over 2 hr, and retained antibacterial activity upon a repeated challenge.

Periprosthetic infection is a devastating consequence of implant insertion and can arise from hematogenous sources or surgical contamination. Microbes can preferentially colonize the implant surface and, by forming a biofilm, escape immune surveillance. We hypothesized that if an antibiotic can be tethered to a titanium alloy (Ti) surface, it will inhibit bacterial colonization, prevent biofilm formation, and avert late-stage infection. To test this hypothesis, a Ti rod was covalently derivatized with vancomycin. Reaction efficiencies were evaluated by colorimetric and spectrophotometric measurements. The vancomycin-modified surface was stable in aqueous solutions over extended time periods and maintained antibiotic coverage, even after pressfit insertion into a cadaverous rat femora. When evaluated using fluorescently labeled bacteria, or by direct colony counts, the surface-bound antibiotic prevented bacterial colonization in vitro after: (1) exposure to high levels of S. aureus; (2) extended incubation in physiological buffers; and (3) repeated bacterial challenges. Importantly, whereas the vancomycin-derivitized pins prevented bacterial colonization, S. aureus adhered to control pins, even in the presence of concentrations of vancomycin that exceeded the strain MIC. These results demonstrate that we have effectively engineered a stable, bactericidal Ti surface. This new surface holds great promise in terms of mitigating or preventing periprosthetic infection. ß

Antibiotic concentrations associated with antibiotic bone cements may cause skeletal cell toxicity and prevent fracture healing. We investigated toxicity effects of dose and treatment time after exposure to three antibiotics commonly used in orthopaedic local drug delivery systems. We hypothesized a threshold exists for toxicity of osteoblasts and chondrocytes after treatment with ciprofloxacin, vancomycin, or tobramycin. To test this hypothesis, we first determined whether treatment with antibiotics caused differences in cellular morphology. Cells exposed to ciprofloxacin showed considerable changes in spread, cell membrane, and extensions. We next asked what dosage of antibiotic would cause reductions in osteoblast and chondrocyte cell numbers. Ciprofloxacin at a dose greater than 100 microg/mL and vancomycin and tobramycin at doses greater than 2000 microg/mL severely decreased cellular proliferation. Finally, we questioned whether observed decreases in cell numbers were the result of increased cellular toxicity or senescence. Released lactate dehydrogenase ratios were severely increased in osteoblasts. These data suggest the balance between the targeted microbicidal effects and host cellular toxicity is critical for skeletal cell survival and function.

Biofilm-associated implant-related bone and joint infections are clinically important due to the extensive morbidity, cost of care and socioeconomic burden that they cause. Research in the field of biofilms has expanded in the past two decades, however, there is still an immense knowledge gap related to many clinical challenges of these biofilm-associated infections. This subject was assigned to the Biofilm Workgroup during the second International Consensus Meeting on Musculoskeletal Infection held in Philadelphia USA (ICM 2018) (https://icmphilly.com). The main objective of the Biofilm Workgroup was to prepare a consensus document based on a review of the literature, prepared responses, discussion, and vote on thirteen biofilm related questions. The Workgroup commenced discussing and refining responses prepared before the meeting on day one using Delphi methodology, followed by a tally of responses using an anonymized voting system on the second day of ICM 2018. The Working group derived consensus on information about biofilms deemed relevant to clinical practice, pertaining to: (1) surface modifications to prevent/inhibit biofilm formation; (2) therapies to prevent and treat biofilm infections; (3) polymicrobial biofilms; (4) diagnostics to detect active and dormant biofilm in patients; (5) methods to establish minimal biofilm eradication concentration for biofilm bacteria; and (6) novel anti-infectives that are effective against biofilm bacteria. It was also noted that biomedical research funding agencies and the pharmaceutical industry should recognize these areas as priorities. ß

The gold standard for diagnosing PPI remains bacterial culture, but sensitivity is negatively affected by prior antibiotic exposure, strongly adherent bacteria, slow growing persisters, and biofilms. ESR and CRP are reflective of systemic changes in infection and pose an attractive, less invasive alternative with reasonable sensitivity and specificity. The current study is the first to identify ideal cut-off values for ESR and CRP in THA patients, providing an optimum balance between sensitivity and specificity based on ROC curves.

Peri-prosthetic infection remains a serious complication of joint replacement surgery. Herein, we demonstrate that a vancomycin-containing sol-gel film on Ti alloy rods can successfully treat bacterial infections in an animal model. The vancomycin-containing sol-gel films exhibited predictable release kinetics, while significantly inhibiting S. aureus adhesion. When evaluated in a rat osteomyelitis model, microbiological analysis indicated that the vancomycin-containing sol-gel film caused a profound decrease in S. aureus number. Radiologically, while the control side showed extensive bone degradation, including abscesses and an extensive periosteal reaction, rods coated with the vancomycin-containing sol-gel film resulted in minimal signs of infection. mCT analysis confirmed the radiological results, while demonstrating that the vancomycin-containing sol-gel film significantly protected dense bone from resorption and minimized remodeling. These results clearly demonstrate that this novel thin sol-gel technology can be used for the targeted delivery of antibiotics for the treatment of periprosthetic as well as other bone infections. Keywords: peri-prosthetic infection; osteomyelitis; vancomycin; sol-gel; controlled release Despite the current level of operative success, bone infection remains a major complication of joint replacement surgery, especially after revision surgery. 1 This is borne out by the numbers as the infection rate after revision surgery more than triples. The most serious complication usually involves the development of a periprosthetic infection, requiring removal of the prosthesis, resection of infected soft tissue and bone, placement of an antibiotic cement spacer, prolonged period of systemic antibiotic administration with difficult recovery, and finally, reimplantation. 2,3 A major factor contributing to the development of periprosthetic infection is adherence of bacteria to the implant surface. 4,5 Upon attachment, microorganisms reorganize into specialized communities termed biofilms and produce a protective glycocalyx 6,7 that provides protection against systemic antibiotics. 8 One strategy utilized to overcome the refractivity to treatment engendered by the biofilm is to administer high doses of antibiotics at the bone-implant interface. 2 However, due to the uncontrolled and rapid release of the antibiotic at the target site many of the delivery systems have proved to be of limited value. Moreover, the carrier itself can serve as a nidus for further microbial colonization. [9][10][11] Release from a room temperature processed sol-gel film provides a novel mechanism for the controlled local delivery of drugs or antibiotics. Silica sol-gel based glass has been shown to be an effective carrier for transforming growth factor b1, 12 trypsin inhibitor, 13 vancomycin, 14 and other molecules. 15 Furthermore, because porosity as well as pore size can be varied, predictable and controlled elution kinetics can be generated. We have chosen to test the efficacy of an antibiotic-containi...