Objectives . The objective of this study is to determine an optimal antibiotic-loaded bone cement (ALBC) for infection prophylaxis in total joint arthroplasty (TJA). Methods. We evaluated the antibacterial effects of polymethylmethacrylate (PMMA) bone cements loaded with vancomycin, teicoplanin, ceftazidime, imipenem, piperacillin, gentamicin, and tobramycin against methicillin-sensitive Staphylococcus aureus (MSSA), methicillin-resistant Staph. aureus (MRSA), coagulase-negative staphylococci (CoNS), Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Standardised cement specimens made from 40 g PMMA loaded with 1 g antibiotics were tested for elution characteristics, antibacterial activities, and compressive strength in vitro. . Results. The ALBC containing gentamicin provided a much longer duration of antibiotic release than those containing other antibiotic. Imipenem-loading on the cement had a significant adverse effect on the compressive strength of the ALBC, which made it insufficient for use in prosthesis fixation. All of the tested antibiotics maintained their antibacterial properties after being mixed with PMMA. The gentamicin-loaded ALBC provided a broad antibacterial spectrum against all the test organisms and had the greatest duration of antibacterial activity against MSSA, CoNS, P. aeruginosa and E. coli. . Conclusion. When considering the use of ALBC as infection prophylaxis in TJA, gentamicin-loaded ALBC may be a very effective choice. Cite this article: Bone Joint Res 2013;2:220–6

There is a lack of carriers for the local delivery of rifampicin (RIF), one of the cornerstone second defence antibiotic for Staphylococcus aureus deep bone infections (DBIs). RIF is also associated with systemic side effects, and known for causing rapid development of antibiotic resistance when given as monotherapy. We evaluated a clinically usedbi-phasic calcium sulphate/hydroxyapatite (CaS/HA) biomaterial as a carrier for dual delivery of RIF with vancomycin (VAN) or gentamicin (GEN). It was hypothesized that this combined approach could provide improved biofilm eradication and prevent the development of RIF resistance. Methods: 1) Biofilm eradication: Using a modified crystal violet staining biofilm quantification method, the antibiotics released at different time points (Day 1, 3, 7, 14, 21, 28 and 35) from the hemispherical pellets of CaS/HA(500 mg)-VAN (24.57 mg) / GEN (10.35 mg) composites with or without RIF (8.11 mg) were tested for their ability to disrupt the preformed 48-h old biofilms of S. aureus ATCC 25923, and S. aureus clinical strain P-3 in 96-well microtitre plate. For each tested group of antibiotic fractions, five separate wells were used (n=5). 2) Testing for resistance development: Similar to the method mentioned above the 48-h biofilm embeded bacteria exposed to antibiotic fractions from different time points continuously for 7 days. The biofilms remained were then tested for RIF resistant strains of bacteria. Overall, there was clear antibiofilm biofilm activity observed with CaS/HA-VAN/GEN+RIF combinations compared with CaS/HA-VAN/GEN alone. The S. aureus strains developed resistance to RIF when biofilms were subjected to CaS/HA-RIF alone but not with combinations of CaS/HA-VAN/GEN+RIF. Enhanced antibiofilm effects without development of RIF resistance indicates that biphasic CaS/HA loaded with VAN or GEN could be used as a carrier for RIF for additional local delivery in clinically demanding DBIs. Acknowledgement: We deeply acknowledge the Royal Fysiographic Society of Lund, Landshövding Per Westlings Minnesfond and the Stina and Gunnar Wiberg fond for financial support

Whilst the SIGN Guidelines state that the use of prophylactic antibiotics in surgery unequivocally reduces major morbidity, reduces hospital costs and is likely to decrease overall consumption of antibiotics they state the chosen antibiotics must reflect local, disease-specific information about the common pathogens and their antimicrobial susceptibility. Growing healthcare concern regarding the rates of Clostridium Difficile (C. Diff) within the hospital setting have led to rationalised and better streamlined prescribing practice within the NHS. In NHS Lanarkshire this led to revised guidelines for prophylactic antibiotic use in Orthopaedics in 2010. Routine use of 3. rd. generation Cephalosporin has been replaced by Flucloxacillin 1g and Gentamicin 1mg/kg. Anecdotally the surgeons within our department were concerned that they were recognising more post-operative renal impairment than before 2010. Our study took 902 consecutive cases treated surgically with either Total Hip Replacement, Total Knee Replacement, Dynamic Hip Screw for fracture and Hemiarthroplasty for fracture since the introduction of the new antibiotic policy. We compared this with a similar number of cases treated with the same operations pre-2010. We looked at the pre admission Urea & Electrolystes compared with immediate post-operative results and applied the definition of Acute Kidney Injury (AKI) as defined by the Acute Kidney Injury Network. A. A rapid time course (less than 48 hours) and B. Reduction of kidney function either as an absolute increase in serum creatinine of ≥26.4μmol/l (≥0.3 mg/dl) or a percentage increase in serum creatinine of ≥50%. Based on this definition we found an increased rate of AKI of 13.7% after the introduction of the use of Gentamicin from 9.8% before its routine use. We wish to highlight that the routine widespread use of Gentamicin may be increasing the rate of acute renal dysfunction seen in Orthopaedic patients undergoing major surgery

C. Difficile infections in elderly patients with hip fractures is associated with high morbidity and mortality. Antibiotic regimens with penicillin and its derivatives is a leading cause. Antibiotic prophylactic preferences vary across different hospitals within NHS. We compared two antibiotic prophylactic regimens - Cefuroxime only prophylaxis and Teicoplanin with Gentamicin prophylaxis in fracture neck of femur surgery, and evaluated the incidence of C. Difficile diarrhea and Surgical Site Infection (SSI). To assess the Surgical Site Infection and C. Difficile infection rate associated with different regimens of antibiotics prophylaxis in fracture neck of femur surgery. Data was analyzed retrospectively. Neck of femur fracture patients treated surgically from 2009 in our unit were included. Age, gender, co morbidities, type of fracture, operation, ASA grade was collected. 1242 patients received Cefuroxime only prophylaxis between January 2009 and December 2012 (Group 1) and 486 patients received Teicoplanin with Gentamicin between October 2015 and March 2017 (Group 2). There were 353 males and 889 female patients in Group 1 and 138 males and 348 female patients in Group 2. The co morbidities in both groups were comparable. Incidence of C. Difficile diarrhea and Surgical Site Infection (SSI) was noted. Statistical analysis with chi square test was performed to determine the ‘p’ value. C. Diff diarrhea rate in Group 2 was 0.41 % as compared to 1.29 % in Group 1. The Surgical Site Infection (SSI) rate in Group 2 was 0.41 % as compared to 3.06 % in Group 1. The comparative results were statistically significant (p = 0.0009). Prophylactic antibiotic regimen of Teicoplanin with Gentamicin showed significant reduction in C. Difficile diarrhea & Surgical Site Infection in fracture neck of femur patients undergoing surgery

The implantation of endoprosthesis is a routine procedure in orthopaedics. Endoprosthesis are mainly manufactured from ceramics, polymers, metals or metal alloys. To ensure longevity of the implants they should be as biocompatible as possible and ideally have antibacterial properties, to avoid periprosthetic joint infections (PJI). Various antibacterial implant materials have been proposed, but have so far only been used sporadically in patients. PJI is one of the main risk factors for revision surgeries. The aim of the study was to identify novel implant coatings that both exhibit antibacterial properties whilst having optimal biocompatibility. Six different novel implant coatings and surface modifications (EBM TiAl6V4, strontium, TiCuN, TiNbN, gentamicin phosphate (GP), gentamicin phosphate+cationic polymer (GP+CP)) were compared to standard CoCrMo-alloy. The coatings were further characterized with regard to the surface roughness. E. coli and S. capitis were cultured on the modified surfaces to investigate the antibacterial properties. To quantify bacterial proliferation the optical density (OD) was measured and viability was determined using colony forming units (CFU). Murine bone marrow derived macrophages (BMMs) were cultured on the surfaces and differentiated into osteoblasts to quantify the mineralisation using the alizarin red assay. All novel coatings showed reduced bacterial proliferation and viability compared to standard CoCrMo-alloy. A significant reduction was observed for GP and GP+CP coated samples compared to CoCrMo (OD. GP,E.coli. = 0.18±0.4; OD. GP+CP,E.coli. = 0.13±0.3; p≤0.0002; N≥7-8). An increase in osteoblast-mediated mineralisation was observed on all surfaces tested compared to CoCrMo. Furthermore, GP and GP+CP coated samples showed a statistically significant increase (M. GP. = 0.21±0.1; M. GP+CP. = 0.25±0.2; p<0.0001; N≥3-6). The preliminary data indicates that the gentamicin containing surfaces have the most effective antibacterial property and the highest osseointegrative capacity. The use of antibiotic coatings on prostheses could reduce the risk of PJI while being applied on osseointegrative implant surfaces

An increasing elderly population means joint replacement surgery numbers are projected to increase, with associated complications such as periprosthetic joint infections (PJI) also rising. PJI are particularly challenging due to antimicrobial resistant biofilm development on implant surfaces and surrounding tissues, with treatment typically involving invasive surgeries and systemic antibiotic delivery. Consequently, functionalisation of implant surfaces to prevent biofilm formation is a major research focus. This study characterises clinically relevant antimicrobials including gentamicin, clindamycin, daptomycin, vancomycin and caspofungin within a silica-based, biodegradable sol-gel coating for prosthetic devices. Antimicrobial activity of the coatings against clinically relevant microorganisms was assessed via disc diffusion assays, broth microdilution culture methods and the MBEC assay used to determine anti-biofilm activity. Human and bovine cells were cultured in presence of antimicrobial sol-gel to determine cytotoxicity using Alamar blue and antibiotic release was measured by LC-MS. Biodegradability in physiological conditions was assayed by FT-IR, ICP-MS and measuring mass change. Effect of degradation products on osteogenesis were studied by culturing mesenchymal stem cells in the presence of media in which sol-gel samples had been immersed. Antimicrobial-loaded coatings showed strong activity against a wide range of clinically relevant bacterial and fungal pathogens with no loss of activity from antibiotic alone. The sol-gel coating demonstrated controlled release of antimicrobials and initial sol-gel coatings showed no loss of viability on MSCs with gentamicin containing coatings. Current work is underway investigating cytotoxicity of sol-gel compositions against MG-63 cells and primary osteoblasts. This research forms part of an extended study into a promising antimicrobial delivery strategy to prevent PJI. The implant coating has potential to advance PJI infection prevention, reducing future burden upon healthcare costs and patient wellbeing

Abstract. OBJECTIVES. Staphylococcus aureus is one of the most common pathogens in orthopaedic biomaterial-associated infections. The transition of planktonic S. aureus to its biofilm phenotype is critical in the pathogenesis of biomaterial-associated infections and the development of antimicrobial tolerance, which leads to ineffective eradication in clinical practice. This study sought to elucidate the effect of non-lethal dispersion on antimicrobial tolerance in S. aureus biofilms. METHODS. Using a methicillin-sensitive S. aureus reference strain, the effect of non-lethal dispersion on gentamicin tolerance, cellular activity, and the intracellular metabolome of biofilm-associated bacteria were examined. Gentamicin tolerance was estimated using the dissolvable bead biofilm assay. Cellular activity was estimated using the triphenyltetrazolium chloride assay. Metabolome analysis was performed using tandem high-performance liquid chromatography and mass spectrometry. RESULTS. Non-lethal dispersion of biofilm-associated S. aureus was associated with a four-fold reduction in gentamicin tolerance and a 25% increase in cellular respiration of both dispersed and adherent cells. Metabolome analysis found non-lethal dispersion reduced intracellular levels of L-ornithine and L-proline, with increased levels of cyclic nucleotides (p<0.05) in both liberated cells and the remaining biofilm-associated bacteria. These metabolomic changes have previously been shown to be associated with inactivation of the carbon catabolite repression mechanism, which is a key regulatory gatekeeper in the cellular resuscitation of dormant S. aureus cells. CONCLUSION. The metabolomic pipeline described in this study presents a valuable tool in the elucidation of molecular mechanistic pathways in biofilm pathogenesis. Kreb's cycle reactivation, through the carbon catabolite repression regulatory mechanism, has been shown to be associated with the reversal of biofilm-associated gentamicin tolerance. Understanding of the biosynthetic changes associated with the biofilm state will assist in the discovery of novel therapeutic targets in the management of biomaterial-related infections. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction and Objective. The continued effectiveness of antibiotic loaded bone cements is threatened by antibiotic resistance. The common antiseptic, chlorhexidine (CHX), is a potential alternative to antibiotics in bone cements, but conventional salts are highly soluble, causing burst release and rapid decline to subinhibitory local CHX concentrations. Here, chlorhexidine triphosphate (CHX-TP), a low solubility CHX salt, is investigated as an alternative antimicrobial in PMMA bone cements. The aim was to assess duration of antimicrobial release and antimicrobial efficacy, along with handling, setting and mechanical properties of CHX-TP loaded cements, compared with an existing cement formulation containing gentamicin. Materials and Methods. Palacos R (Heraeus Medical, Newbury, UK) with 0, 1, 4, 7 and 12% CHX-TP (w/w) cements were prepared by combining solid CHX-TP with Palacos R components, and compared with Palacos R+G. All cements were prepared without vacuum and under ISO 5833:2002 conditions. Cements were tested under ISO 5833:2002 for compressive and bending properties, setting time, maximum temperature and doughing time. Antimicrobial release from the cements into deionised water was studied and antimicrobial efficacy of unaged and aged cements against Staphylococcus aureus (ATCC 29213) was assessed using a disc diffusion assay. Results. Compressive strength of CHX-TP loaded cements was not significantly different to Palacos R or Palacos R+G (p > 0.05, all exceeding ISO 5833:2002 minimum of 70 MPa). Mean bending strength was significantly lower with CHX-TP loading (p < 0.05) than bending strength of Palacos R and Palacos R+G, though all bending moduli exceeded the ISO 5833:2002 minimum (1800 MPa). All cements studied were within the ISO 5833:2002 limits for setting time (3 to 15 min), doughing time (≤ 5 min) and maximum temperature (90 . o. C). Mean doughing time for Palacos R, Palacos R+G and Palacos R + 12 % CHX-TP respectively: 52.5 s, 45 s and 45 s. Mean setting time and mean maximum temperature for Palacos R, Palacos R+G and Palacos R + 1, 4, 7 and 12% CHX-TP respectively: 11.00 min (73 . o. C), 11.25 min (72 . o. C), 12.25 min (66 . o. C), 10.50 min (70 . o. C), 10.00 min (70 . o. C), 10.75 min (62 . o. C). Sustained CHX release into deionised water was observed from all Palacos R + CHX-TP cements. Duration varied according to CHX-TP dosing and diminished over time, although to an extent that itself varied with dosing. 1 % CHX-TP ceased releasing CHX at 6.9 weeks; 4 % CHX-TP ceased at 67.7 weeks; 7 % and 12 % CHX-TP were ongoing at 75.5 weeks. Palacos R+G cements ceased releasing detectable levels of gentamicin after 14.4 weeks. Palacos R+G and Palacos R + CHX-TP cement discs showed efficacy against S. aureus (ATCC 29213) when applied as prepared (unaged) to S. aureus bacterial lawns in disc diffusion assays, with CHX-TP cements showing dose dependency. Zone of inhibition (ZOI) size was significantly reduced for Palacos R+G cements and Palacos R + 1% CHX-TP cements after 1 week and 6 weeks aging, compared to ZOI from unaged cements (p < 0.05). ZOI size produced by Palacos R + 4, 7, and 12 % CHX-TP cements did not decline significantly after 6 weeks aging (p > 0.05). Conclusions. CHX-TP can be incorporated into the Palacos R cement matrix up to 12% w/w without deterioration of compressive strength, bending modulus, doughing time, setting time or maximum temperature. Bending strength was significantly reduced at all CHX-TP loadings studied. Palacos R + 4, 7 and 12% CHX-TP cements provided sustained CHX release, exceeding the duration of gentamicin release from Palacos R+G, and showed sustained efficacy against S. Aureus after 6 weeks aging, which was not achieved by Palacos R+G cements

Staphylococcus aureus is responsible for 60–70% infections of surgical implants and prostheses in Orthopaedic surgery, costing the NHS £120–200 million per annum. Its ability to develop tolerance to a diverse range of antimicrobial compounds, threatens to halt routine elective implant surgery. One strategy to overcome this problem is to look beyond traditional antimicrobial drug therapies and investigate other treatment modalities. Biophysical modalities, such as ultrasound, are poorly explores, but preliminary work has shown potential benefit, especially when combined with existing antibiotics. Using a methicillin-sensitive S. aureus reference strain and the dissolvable bead assay, bacterial biofilms were challenged by gentamicin +/− low-intensity ultrasound (1.5MHz, 30W/cm2, pulse duration 200µs/1KHz) for 20 minutes. The outcome measures were colony-forming units/mL (CFU/mL) and the minimum biofilm eradication concentration (MBEC) of gentamicin. The mean number of S. aureus within control biofilms was 1.04 × 109 CFU/mL. There was no clinically or statistically significant (p=0.531) reduction in viable S. aureus following ultrasound therapy alone. The MBEC of gentamicin for this S. aureus strain was 256 mg/L. The MBEC of gentamicin with the addition of ultrasound was 64mg/L. Low intensity pulsed ultrasound was associated with a four-fold reduction in the effective biofilm eradication concentration of gentamicin; bringing the MBEC of gentamicin to within clinically achievable concentrations

Staphylococcus aureus is responsible for 60–70% infections of surgical implants and prostheses in Orthopaedic surgery, costing the NHS £120–200 million per annum. Its ability to develop resistance or tolerance to a diverse range of antimicrobial compounds, threatens to halt routine elective implant surgery. One strategy to overcome this problem is to look beyond traditional antimicrobial drug therapies and investigate other treatment modalities. Biophysical modalities, such as ultrasound, are poorly explored, but preliminary work has shown potential benefit, especially when combined with existing antibiotics. Using a methicillin-sensitive S. aureus reference strain and the dissolvable bead assay, biofilms were challenged by a low-intensity ultrasound (1.5MHz, 30mW/cm. 2. , pulse duration 200µs/1KHz) for 20 minutes and gentamicin. The outcome measures were colony-forming units/mL (CFU/mL) and the minimum biofilm eradication concentration (MBEC) of gentamicin. The mean number of S. aureus within control biofilms was 1.04 × 10. 9. CFU/mL. There was no clinically or statistically significant (p=0.531) reduction in viable S. aureus following ultrasound therapy alone. The MBEC of gentamicin for this S. aureus strain was 256 mg/L. The MBEC of gentamicin with the addition of ultrasound was 64mg/L. Low intensity pulsed ultrasound was associated with a 4-fold reduction in the effective biofilm eradication concentration of gentamicin; bringing the MBEC of gentamicin to within clinically achievable concentrations

Total joint replacement (TJR), such as hip and knee replacement, is commonly used for the treatment of end stage arthritis. The use of Poly (methylmethacrylate) bone cement is a gold standard in such replacement, where it fixes the implant in place and transfer stresses between bone and implant, and frequently used for local delivery of drugs such as antibiotics. The use of antibiotic loaded bone cement is considered a well-established standard in the treatment and prophylaxis of Prosthetic joint infections (PJI). PJIs is a serious problem that decreases success rate of surgery and can be life threatening to patients, where the incidence can reach up 2% in total and hip replacements and up to 40% for revision surgery. Currently used antibiotic loaded bone cements have many limitations, including burst release of < 10% of antibiotic added. This burst release falls rapidly below inhibitory level within few days, which leads to selection of resistant antimicrobial strains and does not provide prophylaxis from early and delayed stage infection. This study aims to provide a controlled release for gentamicin when loaded on Silica nanoparticles (NP) using layer-by-layer technique (LbL) to provide prophylaxis and treatment from postsurgical infections. The gentamicin loaded NPs were incorporated into PMMA bone cement and the new nanocomposite is characterized for gentamicin release, antimicrobial and mechanical properties. Our results showed that the nanocomposite gentamicin release continued for 30 days at concentration 3 times higher than the commercial formulation containing the same amount of gentamicin, where burst release for few days were observed. Moreover, the nanocomposite showed superior antimicrobial inhibition for bacterial growth and good cytocompatibility without adversely affecting the cement compressive strength, bending and fracture toughness properties

In chronically infected fracture non-unions, treatment requires extensive debridement to remove necrotic and infected bone, often resulting in large defects requiring elaborate and prolonged bone reconstruction. One approach includes the induced membrane technique (IMT), although the differences in outcome between infected and non-infectious aetiologies remain unclear. Here we present a new rabbit humerus model for IMT secondary to infection, and, furthermore, we compare bone healing in rabbits with a chronically infected non-union compared to non-infected equivalents. A 5 mm defect was created in the humerus and filled with a polymethylmethacrylate (PMMA) spacer or left empty (n=6 per group). After 3 weeks, the PMMA spacer was replaced with a beta-tricalcium phosphate (chronOs, Synthes) scaffold, which was placed within the induced membrane and observed for a further 10 weeks. The same protocol was followed for the infected group, except that four week prior to treatment, the wound was inoculated with Staphylococcus aureus (4×10. 6. CFU/animal) and the PMMA spacer was loaded with gentamicin, and systemic therapy was applied for 4 weeks prior to chronOs application. All the animals from the infected group were culture positive during the first revision surgery (mean 3×10. 5. CFU/animal, n= 12), while at the second revision, after antibiotic therapy, all the animals were culture negative. The differences in bone healing between the non-infected and infected groups were evaluated by radiography and histology. The initially infected animals showed impaired bone healing at euthanasia, and some remnants of bacteria in histology. The non-infected animals reached bone bridging in both empty and chronOs conditions. We developed a preclinical in vivo model to investigate how bacterial infection influence bone healing in large defects with the future aim to explore new treatment concepts of infected non-union

Staphylococcus aureus is the main cause of osteomyelitis and forms biofilm and staphylococcal abscess communities (SACs) in humans. While S. aureus has several toxins with specificity for human targets and working with human host cells would be preferred, for SACs no in vitro models, two-dimensional (2D) or three-dimensional (3D), have been described in literature to date. Advanced 3D in vitro cell culture models enable the incorporation of human cells and resemble in vivo tissue more closely than conventional 2D cell culture. Therefore, the aim of this study was to develop an in vitro model of SACs by using a 3D system. The model should allow for studies into antibiotic tolerance and S. aureus - human host cells interactions. With a clinical isolate (S. aureus JAR) or a lab strain (S. aureus ATCC 49230-GFP), SACs were grown in a collagen gel (1.78 mg/ml, Gibco) supplemented with 200 µl human plasma at 37 °C. Transmission and scanning electron microscopy was used to obtain a detailed overview of SACs, whereas immunofluorescent stainings were done to determine whether the pseudocapsule around SACs consist of fibrin. Antibiotic tolerance of SACs was assessed with 100× the minimal inhibitory concentration (MIC) of gentamicin (Roth). Bacterial clearance of non-establised SACs and established SACs with or without pseudocapsule was determined by exposure to differentiated PLB neutrophil-like cells (differentiation with 1.25% DMSO and 5% FBS for 5 days; dPLB) or primary neutrophils isolated with lymphoprep from fresh heparin blood. Degradation of the pseudocapsule was done with 7.5 µl/ml plasmin (Sigma). Colony forming unit (CFU) counts were performed as quantification method. Statistical analysis was performed with the ANOVA multiple comparison test or, when data was not normally distributed, with a Mann-Whitney U test. We have developed a 3D in vitro model of SACs which after overnight growth were on average 200 micrometers in diameter, consisted of 8 log10 CFUs and were surrounded by an inner and outer fibrin pseudocapsule. The in vitro grown SACs tolerated 100× the MIC of gentamicin for 24h and did not significantly differ from control SACs (p=0.1000). dPLB neutrophil-like cells or primary neutrophils did not clear established in vitro SACs (p=0.1102 and p=0.8767, respectively). When the fibrin pseudocapsule was degraded by the enzyme plasmin, dPLB neutrophil-like cells or primary neutrophils caused for a significant decrease in total CFU compared the SACs that did had a pseudocapsule (p=0.0333 and p=0.0272, respectively). The in vitro SACs model offers a tool for host-pathogen interaction and drug efficacy assessments and is a valuable starting point for future research

Clinical experience indicates the beneficial effects of antibiotic-loaded bone cement. Although in vitro studies have shown the formation of a biofilm on its surface they have not considered the gap between the cement and the bone. We have investigated bacterial survival in that gap. Samples with gaps 200 μm wide were made of different bone cements. These were stored dry (‘pre-elution’) or submersed in phosphate-buffered saline to simulate the initial release of gentamicin (‘post-elution’). The gaps were subsequently inoculated with bacteria, which had been isolated from infected orthopaedic prostheses and assessed for their sensitivity to gentamicin. Bacterial survival was measured 24 hours after inoculation. All the strains survived in plain cements. In the pre-elution gentamicin-loaded cements only the most gentamicin-resistant strain, CN5115, survived, but in post-elution samples more strains did so, depending on the cement tested. Although high concentrations of gentamicin were demonstrated in the gaps only the gentamicin-sensitive strains were killed. This could explain the increased prevalence of gentamicin-resistant infections which are seen clinically

Introduction and Objective. Management of bone loss associated with bone contamination or infection represents a double biological and clinical challenge frequent in traumatology. The advent of new biomaterials can allow a different approach in the treatment of bone gap. The purpose of this study was to evaluate the prophylactic and therapeutic effectiveness of addition of a new absorbable bone substitute (BS) eluting different antibiotics in reconstruction of bone defects after infections and fractures with soft tissue damage. Materials and Methods. We conducted a review of patients with contaminated or infected bone defects treated using a new biomaterial, a porous composite of collagen matrices and Beta tricalcium phosphate (β TCP), able to provide a long-term release of different antibiotics. We have included treatment of osteomyelitis and osteosynthesis of exposed fracture (Gustilo Anderson 1–3b) or fractures with soft tissue damage and high risk of contamination. Surgical technique included debridement filling bone defect with BS eluting antibiotics, osteosynthesis (plate, nail, external fixator, kirschner wire), soft tissue coverage, and systemic antibiotic therapy. Radiographic and clinical data including complications (wound dehiscence, superficial or deep infection, osteomyelitis) were collected. Results. We treated 25 patients (21 male, 4 female) with mean age 47 yrs. (range 21–83). The locations treated (for incidence) was: 9 femurs (7 plates, 2 nail), 7 calcanei (one bilateral), 3 tibias, 2 forearms, 2 metatarsi, 2 hands, 1 elbow. 6 patients had large bone loss. 7 patients had bone infections (4 were Cierny Madern 4); 8 patients had osteosynthesis of exposed fractures Gustilo Anderson 1–3b (9 plate, one bilateral calcaneus). 8 patients had treatment for pseudoarthrosis of exposed fractures (6 femurs, 1 forearm, 1 metatarsus) and 3 patients a prophylactic treatment for calcaneal fractures with soft tissue damage. 4 deep infection were treated with multiple surgical debridement and new filling bone defect with BS eluting antibiotic with infection eradication. We have used a combination of vancomycin and gentamicin on 15 cases, vancomycin alone on 4 cases, combination of vancomycin and amikacin on 1 case and amikacin and Linezolid in a targeted multi drug resistance. At final follow-up functional outcome was good in all cases with bone healing. Conclusions. Extensive debridement is a fundamental requisite for eradication of bone infections and contamination. Filling of the bone void with loaded bio-composite eluting diversifiable local antibiotics with synergistic anti-biofilm activity is desirable. Treatment of this bone defects are advantaged when combining his reconstruction with BS and the possibility of release high antibiotic concentration at least for 10 days. This is an important complementing prophylactic and therapeutic antimicrobial option with adjuvant role to systemic therapy that enlarges the success rate

Background. Antibiotic loaded bone cement spacers are used as an adjunct to treatment in 2-stage arthroplasty revisions. If release of the correct choice of antimicrobials is optimised, systemic therapy might be curtailed and emergence of resistance minimised. Aims: To determine the elution period of antimicrobials from bone cement with and without a copolymer, polyvinylpyrrolidone (PVP) and to limit resistance development by the use of two or more antimicrobials. Methods. Triclosan, gentamicin and clindamycin with and without (PVP) in CMW bone cement, was tested against six bacteria using serial plate transfer. Results. While there was little difference between clindamycin and clindamycin with PVP, and between gentamicin and gentamicin with PVP, there was marked enhancement of release of triclosan with PVP. Resistance developed when antimicrobials were used singly but not when used in combination. Conclusion. The addition of water soluble PVP was expected to enhance elution of antimicrobials from bone cement. This occurred with triclosan, a poorly water-soluble agent, but there was no significant difference for gentamicin and clindamycin, which as preferentially water -soluble. Other copolymers are being explored in an attempt to enhance their release. Triclosan used in combination extended the duration of activity against the test bacteria without development of resistance. Combinations of antimicrobials reduce the risk of paradoxical resistance in bone cement

Objectives. Thermal stability is a key property in determining the suitability of an antibiotic agent for local application in the treatment of orthopaedic infections. Despite the fact that long-term therapy is a stated goal of novel local delivery carriers, data describing thermal stability over a long period are scarce, and studies that avoid interference from specific carrier materials are absent from the orthopaedic literature. Methods. In this study, a total of 38 frequently used antibiotic agents were maintained at 37°C in saline solution, and degradation and antibacterial activity assessed over six weeks. The impact of an initial supplementary heat exposure mimicking exothermically curing bone cement was also tested as this material is commonly used as a local delivery vehicle. Antibiotic degradation was assessed by liquid chromatography coupled to mass spectrometry, or by immunoassays, as appropriate. Antibacterial activity over time was determined by the Kirby-Bauer disk diffusion assay. Results. The heat exposure mimicking curing bone cement had minimal effect on stability for most antibiotics, except for gentamicin which experienced approximately 25% degradation as measured by immunoassay. Beta-lactam antibiotics were found to degrade quite rapidly at 37°C regardless of whether there was an initial heat exposure. Excellent long-term stability was observed for aminoglycosides, glycopeptides, tetracyclines and quinolones under both conditions. Conclusions. This study provides a valuable dataset for orthopaedic surgeons considering local application of antibiotics, and for material scientists looking to develop next-generation controlled or extended-release antibiotic carriers. Cite this article: E. Samara, T. F. Moriarty, L. A. Decosterd, R. G. Richards, E. Gautier, P. Wahl. Antibiotic stability over six weeks in aqueous solution at body temperature with and without heat treatment that mimics the curing of bone cement. Bone Joint J 2017;6:296–306. DOI: 10.1302/2046-3758.65.BJR-2017-0276.R1

Infection of orthopaedic implants is a significant problem, with increased antibiotic resistance of adherent ‘biofilm’ bacteria causing difficulties in treatment. We have investigated the in vitro effect of a pulsed electromagnetic field (PEMF) on the efficacy of antibiotics in the treatment of infection of implants. Five-day biofilms of Staphylococcus epidermidis were grown on the tips of stainless-steel pegs. They were exposed for 12 hours to varying concentrations of gentamicin or vancomycin in microtitre trays at 37°C and 5% CO. 2. The test group were exposed to a PEMF. The control tray was not exposed to a PEMF. After exposure to antibiotic the pegs were incubated overnight, before standard plating onto blood agar for colony counting. Exposure to a PEMF increased the effectiveness of gentamicin against the five-day biofilms of Staphylococcus epidermidis. In three of five experiments there was reduction of at least 50% in the minimum biofilm inhibitory concentration. In a fourth experiment there was a two-log difference in colony count at 160 mg/l of gentamicin. Analysis of variance (ANOVA) confirmed an effect by a PEMF on the efficacy of gentamicin which was significant at p < 0.05. There was no significant effect with vancomycin

Aim. To determine if systemic toxicity occurs after the use of antibiotic loaded calcium sulphate in the treatment (1) of bone and soft tissue infection. Although antibiotic loaded calcium sulphate is increasingly used for the local treatment of bone and soft tissue infection, there is little data to demonstrate that systemic levels generated by local release of antibiotics are safe. For this reason, we routinely assay systemic levels of antibiotics. Methods. Patients with osteomyelitis or soft tissue infection underwent surgical debridement and lavage of the infected tissue in routine fashion. Patients with osteomyelitis were graded with the Cierny-Mader classification. Bone cavities and soft tissue dead spaces were packed with antibiotic loaded calcium sulphate (10–40 cc) loaded with Vancomycin (1–4 g) and Gentamicin (240–960 mg). The wounds were closed over the antibiotic loaded calcium sulphate. Patients underwent serial assays of Vancomycin and Gentamicin levels on the day of surgery and the first two post-operative days. Renal function was also measured. Results. 12 limbs in 10 patients were treated for osteomyelitis or soft tissue infection. There was 1 Cierny-Mader grade 1, 3 Cierny-Mader grade 3, and 2 Cierny-Mader grade 4. Two had deep soft tissue infection alone. There were 3 type A hosts and 7 type B hosts. The patients age ranged from 24 to 89 (mean 54). In patients without renal dysfunction, the systemic levels were either unmeasurable at the first assay, or below the acceptable trough level. (Mean 2.4 and 1.8 for Vancomycin and Gentamycin respectively). They had unmeasurable systemic levels at the third assay. In patients with renal dysfunction, systemic levels were in the therapeutic range determined for systemically administered antibiotics, but these levels remained high and did not decrease until patients had undergone their routine dialysis. Conclusions. In patients treated with antibiotic loaded Stimulan, antibiotic assays are not necessary in patients who have normal renal function, as they clear the systemic absorption as quickly as it is generated. Patients with impaired renal function should have lower doses of antibiotic used for their topically applied carrier, and should undergo assays regularly to ascertain if levels are remaining below the accepted range determined for systemically administered antibiotics. If they remain high, the antibiotic loaded calcium sulphate could be removed. * Stimulan (Biocomposites, Keele, UK)

Prophylactic antibiotics administered prior to joint arthroplasty have become standard practice. Due to concern over the risk that 2nd generation cephalosporins posed to the elderly, as regards clostridium difficile associated infections the antimicrobial management team in our unit changed the protocol for prophylactic antibiotics. As of 1st September 2009, flucloxacillin and gentamicin were preferred over cefuroxime as the first choice of prophylactic antibiotic. However, it was noted that postoperatively patients were experiencing a decrease in renal function. One hundred patients who underwent a total hip replacement following the policy change were randomly selected from the departmental joint arthroplasty database. This group was age and sex matched to 100 patients undergoing their surgery prior to the change. Data was collected on renal function, length of stay, antibiotic and age. Any change in renal function was categorised using the RIFLE criteria. Exclusion secondary to variations from protocol or treatment for femoral neck fractures resulted in a total number of 156 patients with 78 in each arm. The average age for both groups was 64 years. Non-parametric analysis of preoperative and postoperative serum creatinine concentrations and Glomerular Filtration Rate (GFR) demonstrated a significant difference between the two groups, showing that GFR decreased (p=0.041) and serum creatinine concentration increased (p=0.037) in the cohort receiving gentamicin. Classing the impaired renal function as: risk, injury or failure (RIFLE criteria) demonstrated a statistically significant difference for any criterion positive (p=0.016) but no significant difference for the specific RIFLE groups (p=0.068). Acknowledging the small numbers and potential confounders for renal impairment, this study was able to show a difference in renal function for patients receiving gentamicin over cefuroxime as prophylaxis for joint arthroplasty