Aim. Rifampicin and fluoroquinolone based therapy is generally considered as first-choice targeted oral antimicrobial therapy for staphylococcal prosthetic joint infections (PJI) treated with debridement, antibiotics and implant retention (DAIR). Alternative equally effective antimicrobial strategies are urgently needed due to toxicity and drug-drug interactions that frequently occur with this strategy. Data from recent clinical studies suggests equipoise for other antimicrobial treatment regimens. The objective of the Rifampicin Combination Therapy versus Targeted Antimicrobial Monotherapy in the Oral Antimicrobial Treatment Phase of Staphylococcal Prosthetic Joint Infection (RiCOTTA)-trial is to evaluate whether monotherapy with clindamycin is non-inferior to rifampicin/fluoroquinolone combination therapy in patients with staphylococcal PJI that are treated with DAIR. Method. The RiCOTTA-trial is a multicenter, non-inferiority, open-label, randomized controlled trial evaluating clindamycin versus rifampicin/fluoroquinolone combination therapy in the oral treatment phase in patients with staphylococcal PJI managed with DAIR. The trial is performed in 16 hospitals in the Netherlands. Eligible patients are adults with staphylococcal knee or hip PJI managed by DAIR. Patients are included one to six days before antibiotic treatment is switched from intravenous to oral therapy. Patients with a contraindication for rifampicin, with a megaprosthesis or who receive intravenous antibiotics for more than three weeks after initial debridement are excluded. Primary outcome is treatment success one year after finishing antimicrobial treatment. Success is defined as the absence of: i. Infection related re-surgery, ii. New episode of antibiotic treatment for infection of the index joint after the initial treatment phase of 12 weeks, iii. Ongoing use of antibiotics for the index joint at the end of follow-up, iv. Death. The estimated treatment success of rifampicin combination therapy is 85% and the monotherapy strategy is considered not inferior when the difference in treatment success will be less than 10%. Enrolment of 158 patients per group (316 in total) is needed to confirm non-inferiority of monotherapy with a power of 80%. The trial is currently open for enrolment. The study is approved by the Medical Ethics Committee Leiden, the Hague, Delft, the Netherlands and registered under EU trial number 2022-501620-26-00 in Clinical Trial Information System. Conclusions. Currently, the RiCOTTTA study is the largest randomised clinical trial that compares targeted oral monotherapy with rifampicin combination treatment for staphylococcal PJI. Noninferiority of monotherapy would result in a change in national PJI guidelines and enable clinicians to use a more patient-tailored approach when considering antibiotics for patients during the oral treatment phase of PJI

Aim. Periprosthetic joint infections follow 1-3% of arthroplasty surgeries, with the biofilm nature of these infections presenting a significant treatment challenge. 1. Prevention strategies include antibiotic-loaded bone cement; however, increases in cementless procedures means there is an urgent need for alternative local antimicrobial delivery methods. 2. A novel, ultrathin, silica-based sol-gel technology is evaluated in this research as an anti-infective coating for orthopaedic prosthetic devices, providing local antibiotic release following surgery. Method. Reduction in clinically relevant microbial activity and biofilm reduction by antimicrobial sol-gel coatings, containing a selection of antibiotics, were assessed via disc diffusion and microdilution culture assays using the Calgary biofilm device. 3. Proliferation, morphology, collagen, and calcium production by primary bovine osteoblasts cultured upon antibiotic sol-gel surfaces were examined, and cytotoxicity evaluated using Alamar blue staining and lactate dehydrogenase assays. Concentrations of silica, calcium and phosphorus compounds within the cell layer cultured on sol-gel coatings and concentrations eluted into media, were quantified using ICP-OES. Furthermore, cellular phenotype was assessed using alkaline phosphatase activity with time in culture. Results. Low antibiotic concentrations within sol-gel had an inhibitory effect on clinically relevant biofilm growth, for example 0.8 mg ml. -1. tobramycin inhibited clinically isolated S. aureus (MRSA) growth with an 8-log reduction in viable colony forming units. There was no significant difference in metabolic activity between untreated and sol-gel exposed primary bovine osteoblasts in elution-based assays. Reduction (2-fold) in metabolic activity in direct contact assays after 48 hours exposure was likely to be due to increased osteoinduction, whereas no impact upon cell proliferation were observed (p=0.92 at 14 days culture). The morphology of primary osteoblasts was unaffected by culture on sol-gel coatings and collagen production was maintained. Calcium containing nodule production within bovine osteoblastic cells was increased 16-fold after 14 days culture upon sol-gel. Conclusions. The ultrathin sol-gel coating showed low cytotoxicity, strong biofilm reducing activity and antimicrobial activity, which was comparable to antibiotics alone, demonstrating that sol-gel delivery of antibiotics could provide local antimicrobial effects to inhibit PJI growth without the need for bone cement. Future work will develop and evaluate sol-gel performance in an ex vivo explant bone infection model which will reduce the need for animal experimentation

Aim. Local antibiotic treatment for bone and joint infections offers direct delivery of high concentrations of antibiotics with reduced systemic exposure and favourable safety profile. However, the possibility of prolonged release of antibiotics at sub-therapeutic levels creates concern about the possible development of antimicrobial resistance. We investigated patients with recurrent bone and joint infection for evidence of antimicrobial resistance emerging from the use of local antibiotics. Method. 125 patients with recurrent infection (prosthetic joint infection, fracture related infection and osteomyelitis) in the UK between 2007 and 2021 were identified. Electronic patient records (including operative notes, pathology results and prescriptions) were reviewed to extract site of infection, date of surgery, the use of local antibiotics, culture results, empiric and definitive antibiotic therapy. All antibiotic sensitivity results were recorded as sensitive, intermediate or resistant according to contemporary guidelines (BSAC and EUCAST). Results. Local antibiotics were used in 74/125 (59.2%) of patients. Agents used were Gentamicin 53/125 (42.4%), Tobramycin 18/125 (14.4%), and vancomycin in 19/125 (15.2%). Combined gentamicin and vancomycin usage was seen in 16/125 patients (12.8%). Gentamicin non-sensitivity was common in this cohort with frequent aminoglycoside use. At index procedure, a Gentamicin non-sensitive organism was cultured in 51/125 patients (40.8%). At re-operation this proportion was lower: 40/125 (32%). There was no statistically significant difference in the rate of Gentamicin resistance at reoperation comparing patients who previously received local aminoglycosides with those who had not (21/71, 29.8% vs 19/54, 35.2% p=0.6, chi-squared test). In 48/125 (38.4%) of patients, the same species was isolated during the index and recurrence surgery. We identified 7 cases with new aminoglycoside resistance arising at the second procedure. In 2/7 – S. aureus and E. faecalis - aminoglycoside resistance was the only change in antimicrobial sensitivity. In 5/7, there were at least 2 additional changes in observed antimicrobial sensitivity. 3/74 (4%) of cases who initially received local aminoglycoside cultured organisms with aminoglycoside resistance at recurrence. 4/51 (7.8%) of those who did not receive local or systemic aminoglycoside at index surgery cultured resistant organisms (chi square 0.82; p=0.365). Conclusions. As a group, patients whose treatment for orthopaedic infection included local antibiotics did not exhibit higher rates of specific antimicrobial resistance compared with those not treated with local antibiotics. However we did identify cases where Gram positive bacteria developed aminoglycoside resistance regardless of their initial antimicrobial therapy. This should be considered in antimicrobial choice during surgery for recurrence

Aim. In 10% of the presumed aseptic hip or knee revisions, a low-grade infection is unexpectedly diagnosed based on the tissue samples taken during revision. Extended antimicrobial prophylaxis can possibly reduce the failure rate in cases of unexpected PJI, because the prophylaxis can be considered as early empiric treatment. In this randomized controlled study we analysed whether extended antimicrobial prophylaxis compared to a single dose is beneficial to improve the outcome of treatment in unexpected PJI in revision arthroplasty. Method. This study was nested in a randomized clinical trial comparing single-dose cefazolin with prolonged prophylaxis (15 doses of cefazolin over 5 days) for revision arthroplasty of the hip or knee. For this analysis, patients were included if an unsuspected PJI (defined as ≥2 positive intraoperative tissue samples with the same microorganism) was diagnosed. PJI treatment consisted of 12 weeks of a rifampicin-based regimen in Staphylococcal PJI, without removal of the prosthesis. We examined Infection characteristics and success of treatment after one year, defined as the absence of signs or treatment for PJI during follow-up. Results. After randomization of 662 patients, 68 unexpected PJI were diagnosed. In 5 cases no antimicrobial treatment was started. The success rate after one year follow-up for those who received PJI treatment was 96% (28/29) in the single dose group and 91% (31/34) in the extended prophylaxis group (p=1.00). The most frequently identified pathogens in unexpected PJI were Cutibacterium acnes (n=50) and Staphylococcus epidermidis (n=14). The causatives were susceptible for the cefazolin prophylaxis in 61 of the 63 cases. The interval between the stopped prophylaxis and the re-start of antimicrobial treatment was on average 10 days (SD 4) for the single dose and 5 days (SD 4) for the extended group. The mean duration of antimicrobial treatment was 83 days (SD 12) and did not differ between both groups (p=0.16). Conclusions. This is the first randomized controlled trial in which extended prophylaxis showed no benefit on the prosthesis survival for patients with an unexpected PJI after assumed aseptic revision of the hip or knee prosthesis. The results imply that extended prophylaxis should not be given as part of early empiric therapy

Aim. The use of medical devices has grown significantly over the last decades, and has become a major part of modern medicine and our daily life. Infection of implanted medical devices (biomaterials), like titanium orthopaedic implants, can have disastrous consequences, including removal of the device. For still not well understood reasons, the presence of a foreign body strongly increases susceptibility to infection. These so-called biomaterial-associated infections (BAI) are mainly caused by Staphylococcus aureus and Staphylococcus epidermidis. Formation of biofilms on the biomaterial surface is generally considered the main reason for these persistent infections, although bacteria may also enter the surrounding tissue and become internalized within host cells. To prevent biofilm formation using a non-antibiotic based strategy, we aimed to develop a novel permanently fixed antimicrobial coating for titanium devices based on stable immobilized quaternary ammonium compounds (QACs). Method. Medical grade titanium implants (10×4×1 mm) were dip-coated in a solution of 10% (w/v) hyperbranched polymer, subsequently in a solution of 30% (w/v) polyethyleneimine and 10 mM sodium iodide, using a dip-coater, followed by a washing step for 10 min in ethanol. The QAC-coating was characterized using water contact angle measurements, scanning electron microscopy, FTIR, AFM and XPS. The antimicrobial activity of the coating was evaluated against S. aureus strain JAR060131 and S. epidermidis strain ATCC 12228 using the JIS Z 2801:2000 surface microbicidal assay. Lastly, we assessed the in vivo antimicrobial activity in a mouse subcutaneous implant infection model with S. aureus administered locally on the QAC-coated implants prior to implantation to mimic contamination during surgery. Results. Detailed material characterization of the titanium samples showed the presence of a homogenous and stable coating layer at the titanium surface. Moreover, the coating successfully killed S. aureus and S. epidermidis in vitro. The QAC-coating strongly reduced S. aureus colonization of the implant surface as well as of the surrounding tissue, with no apparent macroscopic signs of toxicity or inflammation in the peri-implant tissue at 1 and 4 days after implantation. Conclusions. An antimicrobial coating with stable quaternary ammonium compounds on titanium has been developed which holds promise to prevent BAI. Non-antibiotic-based antimicrobial coatings have great significance in guiding the design of novel antimicrobial coatings in the present, post-antibiotic era

Aim. Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is commonly associated with serious cases of community-onset skin and musculoskeletal infections (Co-SMSI). Molecular epidemiology analysis of CA-MRSA recovered from skin and soft tissues specimens is lacking in Latin America. This study aimed to identify phenotypic and genotypic features of MRSA isolates recovered from patients presenting Co-SMSI. Methods. Consecutive MRSA isolates recovered from Co-SMSI of patients admitted from March 2022 to January 2023 in a Brazilian teaching hospital were tested for antimicrobial resistance and characterized by their genotypic features. Identification was carried out by automated method and through MALDI-TOF MS. Antimicrobial susceptibility was tested by disk diffusion, broth microdilution and E-test strips for determination of the minimal inhibitory concentration (MIC) according to recommendations from the Brazilian Committee on Antimicrobial Susceptibility Testing (BrCAST) and European Committee on Antimicrobial Susceptibility Testing (EUCAST). Gene mecA characterization and Sccmec typing were performed by multiplex polymerase chain reaction (PCR) assay, and gene lukF detection by single PCR. Patients were prospectively followed up for two months, in order to determine their clinical characteristics and outcomes. Results. Overall, 48 Staphylococcus aureus isolates were obtained from 68 samples recovered from patients with Co-SMSI. Twenty two (42%) were phenotypically characterized as MRSA, although mecA gene was only identified in 20 of those samples. Sccmec was untypable in 12 isolates, Sccmec was type II in 4 isolates and 2 were classified as type IVa. LukF gene was identified in 5 isolates. Antimicrobial resistance profile showed that all isolates were susceptible to linezolid and vancomycin with MIC = 1 and MIC = 2 in 66,7% and 33.3%, respectively. Susceptibility to quinolones was worryingly low and none of the isolates were sensitive to usual doses of ciprofloxacin and levofloxacin, and showed increased rates of resistance to increased exposure to these drugs, as well. Isolates were both susceptible to gentamicin and tetracycline in 85% and resistance to also Sulfamethoxazole/Trimethoprim occurred in only 2 isolates. Mortality rate evaluated within 1 month of the initial evaluation was 10% among MRSA isolates. Conclusions. Our results showed that CA-MRSA isolates causing Co-SMSI demonstrated an alarming pattern of multidrug resistance, including to β-lactam and quinolones, which have been commonly prescribed as empirical therapy for patients with skin, soft tissue and musculoskeletal infections

Background. Treatment of staphylococcal prosthetic joint infection (PJI) usually consists of surgical debridement and prolonged rifampicin combination therapy. Tailored antimicrobial treatment alternatives are needed due to frequent side effects and drug-drug interactions with rifampicin combination therapy. We aimed to assess the effectiveness of several alternative antibiotic strategies in patients with staphylococcal PJI. Methods. In this prospective, multicenter registry-based study, all consecutive patients with a staphylococcal PJI, treated with DAIR or one-stage revision surgery between January 1. st. , 2015 and November 3. rd. , 2020, were included. Patients were treated according to a predefined protocol for PJI. Antimicrobial treatment strategies differed between centers, which was accepted and used as pseudorandomization. Depending on the hospital patients were admitted to, they were treated with either a long-term rifampicin strategy (consisting of 12 weeks rifampicin combination therapy) ore one of several short-term rifampicin strategies, consisting of only five days of rifampicin combination treatment, started immediately postoperative, followed by clindamycin, flucloxacillin or vancomycin monotherapy. Patients were stratified in different groups, depending on the used antimicrobial strategy. Cox proportional hazards models were used to compare outcome between the groups. Results. Two hundred patients were included and, based on the antimicrobial treatment, stratified in one long-term rifampicin group (n=23) or one of the three short-term rifampicin groups: clindamycin (n=56), flucloxacillin (n=47), vancomycin (n=26), other (n=48). Outcome of PJI after DAIR or one-stage exchange was not statistically different between patients treated with long-term rifampicin combination therapy and patients treated with clindamycin or flucloxacillin monotherapy including only five days of rifampicin combination therapy. Moreover, treatment duration was four weeks shorter in the clindamycin-based and flucloxacillin-based groups. Adjusted hazard ratios for failure for patients treated with either flucloxacillin or clindamycin were almost equal to patients treated with long-term rifampicin combination therapy (aHR 1.21, 95%CI 0.34–4.40). Conclusions. A short-term rifampicin strategy with either clindamycin or flucloxacillin and only five days of rifampicin was found to be as effective as traditional long-term rifampicin combination therapy. A randomized controlled trial is needed to further address efficacy and safety of alternative treatment strategies for staphylococcal PJI

Aim. Suppressive antimicrobial therapy (SAT) is used worldwide for patients with a prosthetic joint infection (PJI but clear definitions or guidelines regarding the indications, antimicrobial strategy or treatment duration are currently lacking in the literature. The aim of this study was to identify the global differences in the clinical practice of SAT for PJI. Method. An online survey was designed to investigate the current opinion on indication and treatment goals, preferred antimicrobial drugs, dosing and treatment duration and follow-up of patients with PJI on suppression. The survey was distributed using e-mail lists of several international bone and joint infection societies and study groups. Recipients were asked to share the survey with colleagues who were not a member of one of the societies but who were involved in PJI care. Results. The questionnaire was fully completed by 330 physicians from 43 different countries on six continents (Europe, n=134, 41%; Oceania n=112, 34%; North America, n=51, 16%; other, n=33, 10%; total response rate 14%). Antimicrobial treatment for PJI was discussed in a multidisciplinary team in Europe (90%), Oceania (42%) and North America (12%). In six of eight (75%) different clinical scenarios, respondents from North America would most often place a patient on SAT. In seven of eight (88%) scenarios, SAT was started least often by European respondents. The presence of a fistula was considered a contra-indication for suppression by 74 respondents (22%). First choices of SAT for staphylococcal PJI were: oral cephalosporins (39%) and tetracyclines (31%) in North America; anti-staphylococcal penicillins (55%) and oral cephalosporins (24%) in Oceania; tetracyclines (27%) and anti-staphylococcal penicillins (22%) in Europe. For streptococcal PJI, most clinicians preferred penicillins (91% in Oceania, 67% in Europe, and 53% in North America). Preferred SAT for gram negative PJI was: fluoroquinolones and a penicillin/betalactamase inhibitor in North America (26% and 18%, respectively) and Oceania (23% and 27%, respectively); fluoroquinolones (31%) and Cotrimoxazole (28%) in Europe. The dosage of SAT was never lowered (n=126, 38%), standardly lowered for all antibiotics (n=79, 24%) or only lowered for specific antibiotics (n=125, 38%). SAT was prescribed for an indefinite duration (n=43, 13%), as fixed duration between six months and three years (n=104, 32%) or for an undetermined prespecified duration (n=154, 47%). Conclusions. Substantial variation in the practice of SAT for PJI exists between physicians worldwide and throughout the different continents. This reflects the paucity of data regarding the indication and treatment of PJI with SAT

Aim. Antimicrobial suppression has shown to significantly improve treatment success of streptococcal periprosthetic joint infection (PJI) compared to 12-week standard antimicrobial therapy, however, only short-term follow-up was investigated. In this study we assessed the impact of suppression on the long-term outcome of streptococcal PJI. Method. Consecutive patients with streptococcal PJI (defined by EBJIS criteria) treated 2009–2021 were prospectively included and allocated into standard and suppression (> 6 months) treatment group. Infection-free survival was assessed with Kaplan-Meier-method and compared between the groups with log rank test. Rates of infection-free, streptococcal infection-free and relapse-free status as well as tolerability of suppression were assessed. Results. Sixty-three PJI episodes (36 knee, 26 hip and one shoulder prosthesis) of patients with a median age of 70 (35–87) years were included. Twenty-seven (43%) were females. Predominant pathogens were S. agalactiae (n=20), S. dysgalactiae (n=18) and S. mitis/oralis (n=13). The main surgical procedures used were two-stage exchange (n=35) and prosthesis retention (n=21). Standard 12-week treatment was administered in 33 patients and suppression in 30 patients, of whom 10 had ongoing suppression and 20 had discontinued antibiotics at time of follow-up. Used oral antibiotics for suppression were amoxicillin (n=29), doxycycline (n=5) and clindamycin (n=2); 6 patients changed antibiotic substance due to side effects. The median follow-up time was 3.9 (0.3–13.3) years. Infection-free survival after 7.5 years was 38% with standard treatment and 62% with suppression (p=0.038). Of all failures, 52% (14/27) were due to streptococci. Suppression was effective in preventing streptococcal infection for the duration of antimicrobial treatment, however, after discontinuation relapses or new infections due to streptococci occurred in 5/20 (25%) patients and infection with any Streptococcus spp. was observed in 9/19 (47%) failures with standard treatment, 5/6 (83%) failures after discontinuing suppression and none during suppression. All failures in patients with ongoing suppression were caused by gram-negative rods. Conclusion. At long-term follow-up, the success rate was superior with suppression compared to standard treatment. Most failures after stopping suppression were caused by streptococci, whereas failures under suppression were caused by aerobic gram-negative rods

Aim. Antimicrobial resistance (AMR) aggravates an already difficult treatment of periprosthetic joint infections (PJI). The prevalence of drug-resistant pathogens varies across countries and increases over time. Regular monitoring of bacteriological analyses should be performed. Due to many factors influencing the AMR, the correct choice of antimicrobial management remains arguable. The primary purpose of this retrospective study was to identify and compare causative bacteria and to compare the incidence of antibiotic resistance between the septic revision total knee arthroplasty (TKA) and septic revision total hip arthroplasty (THA). Method. A review of all revision TKAs and revision THAs, undertaken between 2007 and 2020 in a tertiary referral centre, was performed. Included were cases meeting the consensus criteria for PJI, in which an organism has been identified. There were no major differences in tissue sampling between revision TKAs and revision THAs over time. Results. A total of 228 bacterial strains, isolated after revision TKA and THA, were analysed for their resistance to 20 different antibiotics. There was a statistically significant higher occurrence of Gram-negative bacteria (p=0.002) and Enterococcus species (p=0.026) identified after revision THAs compared to TKA. The comparison of antibiotic resistance between revision TKAs and revision THAs was statistically significant in 9 of 20 analysed antibiotics. Pathogens isolated after revision THA were much more resistant compared to pathogens isolated after revision TKA. Resistance in revision THAs was significantly higher to oxacillin (p=0.03), ciprofloxacin (p<0.001), levofloxacin (p<0.001), moxifloxacin (p=0.005), clindamycin (p<0.001), co-trimoxazole (p<0.001), imipenem (p=0.01), rifampicin (p=0.005) and tetracycline (p=0.009). There was no significantly higher resistance of pathogens isolated after revision TKAs detected. No statistically significant difference in antibiotic resistance of Gram-negative bacteria between revision TKA and revision THA was observed. Conclusions. The occurrence and the resistance of bacteria to antibiotics differs significantly between revision TKAs and revision THAs. This has implications on of the choice of empirical antibiotic in revision surgery as well as prophylactic antibiotic in primary surgery, depending on the joint that is to be replaced

Staphylococcus aureus is the most frequently isolated organism in periprosthetic joint infections. The mechanism by which synovial fluid (SF) kills bacteria has not yet been elucidated, and a better understanding of its antibacterial characteristics is needed. We sought to analyze the antimicrobial properties of exogenous copper in human SF against S. aureus. SF samples were collected from patients undergoing total elective knee or hip arthroplasty. Different S. aureus strains previously found to be sensitive and resistant, UAMS-1 and USA300 WT, respectively, were used. We performed in-vitro growth and viability assays to determine the capability of S. aureus to survive in SF with the addition of 10µM of copper. We determined the minimum bactericidal concentration of copper (MBC-Cu) and evaluated the sensitivity to killing, comparing WT and CopAZB-deficient USA300 strains. UAMS-1 evidenced a greater sensitivity to SF when compared to USA300 WT, at 12 (p=0.001) and 24 hours (p=0.027). UAMS-1 significantly died at 24 hours (p=0.017), and USA300 WT survived at 24 hours. UAMS-1 was more susceptible to the addition of copper at 4 (p=0.001), 12 (p=0.005) and 24-hours (p=0.006). We confirmed a high sensitivity to killing with the addition of exogenous copper on both strains at 4 (p=0.011), 12 (p=0.011), and 24 hours (p=0.011). Both WT and CopAZB-deficient USA300 strains significantly died in SF, evidencing a MBC-Cu of 50µM against USA300 WT (p=0.011). SF has antimicrobial properties against S. aureus, and UAMS-1 was more sensitive than USA300 WT. The addition of 10µM of copper was highly toxic for both strains, confirming its bactericidal effect. We evidenced CopAZB-proteins involvement in copper effluxion by demonstrating the high sensitivity of the mutant strain to lower copper concentrations. Thus, we propose CopAZB-proteins as potential targets and the use of exogenous copper as possible treatment alternatives against S. aureus

Aim. Antimicrobial peptides occur naturally in our intrinsic immune system. PLG0206 is a novel, engineered, 24-amino acid peptide which has broad-spectrum antimicrobial activity, including in biofilm and against multi-drug resistant pathogens (1,2). This is the first clinical study to evaluate the safety and tolerability of PLG0206 when administered via an irrigation solution in patients with periprosthetic joint infections (PJI) following total knee arthroplasty (TKA) during debridement, antibiotics, and implant retention (DAIR). Secondary objectives were to evaluate pharmacokinetics (PK), biomarkers and initial clinical efficacy at one year post-DAIR procedure. Method. This prospective, multicenter, open-label, interventional study assessed two dose levels of PLG0206. Fourteen patients underwent revision for PJI after TKA. At the end of debridement, they received a single intra-articular irrigation of PLG0206 into the wound cavity lasting 15 minutes at concentrations of 3 mg/mL (n=7) or 10 mg/mL (n=7). Patients received post-operative care and intravenous/oral antimicrobial therapy as per their institutional guidelines. Patients were monitored for safety and signs of relapse or persistent infection for 12 months post study drug administration and PK and blood biomarkers were assessed. Results. All patients completed their final study assessment at Day 365. Over the 1-year follow-up, only one recurrence (7%) was noted at Day 169 in the low-dose cohort. Following dosing, nine patients (64.3%) had limited systemic exposure; maximum plasma concentration occurred 1-hour post-administration and declined rapidly to undetectable levels by 24 hours following treatment in all patients. The incidence of drug related treatment-emergent adverse events (TEAEs) was low. Two patients, both in the higher dose cohort, experienced a transient drug related TEAE; one of hypertransaminasaemia and one of neuralgia. Both events were moderate in severity and resolved within two weeks of onset. Conclusions. A single 15-minute irrigation of PLG0206 into the wound cavity of patients undergoing a DAIR procedure for PJI following TKA, is safe and well tolerated by patients. This new antimicrobial peptide offers a promising therapeutic option in musculoskeletal infection. The initial clinical efficacy is encouraging but now needs to be investigated in a much larger clinical trial

Aim. Success rate of debridement, antimicrobial and implant retention (DAIR) in high suspicion of early PJI after primary arthroplasty is 70–80%. No studies have been performed focusing on outcome of DAIR after revision arthroplasty of the hip (THA) or knee (TKA). The aim of this study is to investigate the outcome of DAIR in suspected early PJI after revision THA or TKA and to identify risk factors for failure. Method. In this retrospective study, we identified early DAIRs after revision THA or TKA performed between January 2012 and August 2019. All patients received empirical antibiotics directly after the DAIR procedure. Antimicrobial treatment was adjusted to the tissue culture results. Success was defined as: 1) implant retention; 2) no repeated revision arthroplasty or supervised neglect after treatment; 3) no persistent or recurrent PJI after treatment and no administration of suppressive antimicrobial therapy; 4) survival of the patient. Infection free success was defined as: 1) no persistent or recurrent PJI after treatment; 2) no administration of suppressive antimicrobial therapy. Results. The overall success rate after one year of 100 cases with early DAIR after revision THA or TKA was 79% and infection free success rate was 85%. In PJI cases, empirical antimicrobial mismatch with causative micro-organisms was associated with lower success rate (70%) than non-mismatch (95%) (p=0.02). No patients from the non-PJI group failed after one year versus 13 failures within the PJI group. A consecutive DAIR within 90 days after the first DAIR was warranted in 24 cases. Only 4 of 20 PJI cases failed despite the consecutive DAIR. Conclusions. In high suspicion of early PJI after revision arthroplasty, DAIR is a good treatment option with comparable outcome with DAIR after primary arthroplasty. A consecutive DAIR should not be avoided when infection control fails within 90 days after the first DAIR to prevent explantation of the prosthesis. Antimicrobial mismatch is associated with failure and should be avoided

Aims. Prosthetic joint infection (PJI) remains the most severe complication of arthroplasty. Failure of intensive, long-term antibiotic treatment for PJI often requires removal of the implant. Antibiotic failure is thought to be caused by biofilm and persister formation. Novel anti-biofilm and anti-persister strategies are urgently needed. Here, we investigated the effects of several antimicrobial peptides on the bacteria within antibiotic-treated biofilms in an in vitro mature biofilm model on abiotic surfaces. Methods. On polystyrene, a mature (7 day-old) methicillin-resistant Staphylococcus aureus (MRSA) biofilm was developed. Thereafter, bacteria in the biofilm were exposed to rifampicin and ciprofloxacin (both 10× >MIC) for three days. Surviving bacteria in the antibiotic-treated biofilm, presumed to include persisters, were exposed to increasing doses of the antimicrobial peptides SAAP-148, acyldepsipeptide 4 (ADEP4), LL-37 and pexiganan. SAAP-148 was further tested on antibiotic-treated mature biofilms on titanium/aluminium/niobium (TAN) discs and prosthetic joint liners. Results. Daily exposure of the mature biofilm for seven days with antibiotics resulted in a 4-log reduction of MRSA without elimination of the bacteria. The surviving bacteria within the biofilm were eliminated upon subsequent exposure to SAAP-148 and pexiganan but not with LL-37 ad ADEP4. Antibiotic treatment of mature biofilms on TAN discs followed by SAAP-148 also resulted in eradication of bacteria within the biofilm. SAAP-148 also fully eliminated bacteria within antibiotic-treated mature MRSA biofilms on an ex vivo liner of a prosthetic joint. Conclusions. A novel mature biofilm model has been developed in which the efficacy of antimicrobial peptides against bacteria, including persisters, residing within a biofilm was investigated. SAAP-148 and pexiganan were highly effective against the bacteria residing in antibiotic-exposed mature MRSA biofilms. This in vitro model system will be used to analyze the effects of novel antibiotic strategies and other anti-PJI agents

Aim. Fracture-related infection (FRI) is a serious complication after trauma. More often resistant micro-organisms are cultured. Gentamicin covers a wide variety of causative agents for FRI. A bio-absorbable antibiotic carrier, Cerament-G®, combines dead space management with local release of gentamicin in a one-stage approach. The achieved tissue concentrations of locally applied antibiotics are 4–8 thousand times higher than after systemic administration. Does Cerament-G® have antimicrobial activity towards bacteria that are not susceptible to systemic gentamicin administration. Method. The four most often cultured bacterial species found in FRI were used; Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Enterobacter cloacae. For each species, four different isolates were obtained, each with a different susceptibility for gentamicin. This susceptibility, expressed in the minimal inhibitory concentration (MIC), varied from completely susceptible (MIC 0,064 mg/L – 4mg/L), minimal resistance (4mg/L – 16mg/L), moderate resistance (8 mg/L – 96 mg/L) to high resistance (24 mg/L - >1024 mg/L), depending on each different organism. Antimicrobial activity of Cerament-G. ®. was determent by a Kirby-Bauer test, according to the EUCAST disc protocol. Each test was done in five-fold for each of the 16 cultured isolates, four of each species. The zone of inhibition (ZOI), obtained by the test, was compared between each bacterial isolate and within each of the four separate species. Results. Cerament-G. ®. shows antimicrobial activity against S. aureus, S. epidermidis, P. aeruginosa and E. cloacae. ZOI-values varied from 11 to 44 mm. It was negatively correlated with the MIC; the higher the MIC, the less the antimicrobial effect of Cerament-G. ®. Between bacterial isolates with the same MIC, within the same species, there was no significant difference in ZOI between the five-fold repetitions of the test, indicating an accurate test. The ZOI of the different bacterial isolates (with different MIC's), belonging to the same bacterial species, differed significantly. Of all 16 isolates, only the S. aureus with a MIC of >1024 mg/L did not show antimicrobial activity of Cerament-G. ®. ; ZOI =0mm. Conclusions. This study shows that Cerament-G. ®. has antimicrobial activity against bacterial isolates, resistant to gentamicin when systemically treated. This confirms that the cut-off point for systemic application is not very useful for the local use of Cerament-G. ®. and emphasizes the need for optimization and change of current antibiotic protocols to increase the durability and sustainability of antibiotic FRI treatment

Aim. Treatment of enterococcal periprosthetic joint infections (PJI) is challenging due to heterogeneous pathogenesis, non-standardized management strategies and lack of biofilm-active antibiotics. Previous studies report treatment success from 50–76%. We evaluated the characteristics and outcome of enterococcal PJI, in particular the influence of antimicrobial treatment regimens. Method. Consecutive patients with enterococcal PJI treated at two specialized orthopaedic institutions were retrospectively included from 2010 to 2017. PJI was defined by the proposed European Bone and Joint Infection Society (EBJIS) criteria. Adequate antimicrobial treatment was considered when the antibiotic was appropiate for the treatment of enterococcal bone infections (activity, dose, oral bioavailability, bone penetration). The treatment success (defined as no relapse of enteroccal infection) and clinical success(i.e. infection-free status) was evaluated and compared using Fishers exact test. Results. We included 75 episodes with enterococcal PJI, involving 41 hip, 30 knee, 2 elbow, 1 shoulder prosthesis. The median patient age was 76 years (range, 30–90 years), 48 (64%) were female. The infection occurred perioperatively in 61 episodes (81%), haematogenously in 13 (17%) and by contiguous spread in 1 case. Sinus tract was present in 16 patients (21%), predominantly in polymicrobial compared to monomicrobial infections (13 vs. 3 episodes, p= 0.01). Preoperative serum C-reactive protein level was elevated in 63/75 patients (84%) and synovial fluid leukocyte count was increased in 25/29 patients (86%). Enterococci grew in synovial fluid in 76%, in periprosthetic tissue in 78% and in sonication fluid in 73% of patients. Predominantly, E. faecalis was identified (n=64), followed by E. faecium (n=10) and E. casseliflavus (n=1); mixed infections were diagnosed in 38 patients (51%). Two-stage prosthesis exchange was performed in 44 (59%), debridement and retention in 13 (17%), resection arthroplasty in 11 (15%) and one-stage exchange in 10 patients (13%). Of 66 patients with available follow-up data (median, 31.8 months; range, 0.3–83.3 months), the treatment success was 85% (56/66), however, clinical success was only 68% (45/66). Treatment success was similar in monomicrobial and polymicrobial infections. Adequate antimicrobial treatment was associated with significant better outcome (91% vs. 38%, p=0.002). Treatment with fosfomycin (19/20, 95%) and combination therapy (45/50, 90%) was associated with better outcome, however, did not reach statistical significance (p >0.05). Conclusions. The treatment outcome of enterococcal PJI was high (85%), however, a second episode of PJI caused by a new pathogen was common in the later course. Adequate antimicrobial treatment was the only significant factor associated with better treatment success

Acrylic bone cements are used rather extensively in orthopedic and spinal applications. The incorporation of calcium phosphate additives to bone cements, to induce osteoconductivity, have typically resulted in increased cement viscosity, decreased handling, and detrimental effects of the mechanical performance of the cement. Additionally, bioactive bone cements are offered at a premium cost, which limits clinical use of these materials. The goal of this study was to examine and characterize an alternative two-solution poly (methyl Methacrylate) (PMMA) bone cement (referred to as TSBC), after incorporation of several calcium phosphate additives and antimicrobials. These bioactive and antimicrobial two-solution cements were designed to have adjustable properties that meet specific requirements of orthopedic applications. The addition of a bioactive agent would lead to increased levels of bone reformation after surgery, while an antibiotic within the cement would decrease the ability for pathogens to grow in the interface between the bone and new implant. TSBC is a pre-mixed bone cement that exhibits a combination of attractive properties including high strength, adjustable viscosity, adequate exothermal properties, as well as offering the possibility of using the same batch multiple times. The addition of antibiotics has not been previously explored in two-solution bone cements. Therefore, it is desirable to induce antibacterial activity with this formulation. Hydroxyapatite (Ca5(PO4)3(OH)), Brushite (CaHPO4•2H2O), and Tricalcium Phosphate (Ca3(PO4)2)(TCP) were incorporated into the TSBC in varying concentrations (25 and 50 wt%), and the rheological characteristics were examined to verify the feasibility of adding high concentrations of fillers to this cement formulation. Results demonstrated that unlike commercial powder-liquid formulations, calcium phosphate additives in TSBC do not detrimentally affect handling and the rheological properties of the material, while also providing maintenance of cement strength and other physical properties. TSBC material spends a dramatically increased amount of time in the swelling phase, as compared to powder-liquid formulations and thus is better suited to incorporate additives fully into its polymer matrix. Current two-solution bone cements do not contain any osteoconductive or antimicrobial agents. This study investigated the effects of addition of these bioactive agents in the physical and mechanical properties of the cement. Cement porosity was investigated to ensure that the porous nature of the bioactive cement does not damage the mechanical stability of the material. Further imaging will be conducted to demonstrate the improved osteointegration of these bioactive cement with osteoblasts (Figure 1). Degradation studies have been conducted to validate the biodegradable properties of the bioactive components and antibiotics release profile. It is further hypothesized that the degradation time will correlate to the antimicrobial activity. As the cement is replaced with natural bone, more and more antimicrobial will become exposed to the physiologic environment causing a continuous antimicrobial release as the material is partially replaced with new bone over time. Antimicrobial effectiveness and antimicrobial release studies are under-way to illustrate the cements ability to restrict growth at the cement surface, as well as show the antimicrobial release profile over time

Aim. Tourniquet is widely used in extremity surgery. In order to prevent surgical site infection, correct timing of antimicrobial prophylaxis and tourniquet inflation is important. We aimed to evaluate the time for which the free drug concentration of cefuroxime is maintained above the minimal inhibitory concentration (T>MIC) in subcutaneous tissue and calcaneal cancellous bone during three clinically relevant tourniquet application scenarios. Method. Twenty-four female pigs were included. Microdialysis catheters were placed for sampling of cefuroxime concentrations bilaterally in calcaneal cancellous bone and subcutaneous tissue, and a tourniquet cuff was applied on a randomly picked leg of each pig. Subsequently, the pigs were randomized into three groups to receive 1.5 g of cefuroxime by intravenous injection 15 min prior to tourniquet inflation (Group A), 45 min prior to tourniquet inflation (Group B), and at the tourniquet release (Group C). The tourniquet duration was 90 min in all groups. Dialysates and venous blood samples were collected eight-hours postcefuroxime administration. Results. Cefuroxime concentrations were maintained above the clinical breakpoint MIC for Staphylococcus aureus (4 µg/mL) in calcaneal cancellous bone and subcutaneous tissue throughout the 90 min tourniquet duration in Group A and B. Cefuroxime administration at tourniquet release (Group C) resulted in concentrations above 4 µg/mL for a minimum of 3.5 hours in the tissues on the tourniquet side. There were no significant differences in the T>MIC (4 µg/mL) in subcutaneous tissue or calcaneal cancellous bone between the three groups. However, Group A tended toward shorter T>MIC in tourniquet calcaneal cancellous bone compared to Group C (p=0.08). Conclusions. Administration of cefuroxime (1.5 g) in the 15–45 min window prior to tourniquet inflation resulted in sufficient calcaneal cancellous bone and subcutaneous tissue concentrations throughout the 90 min tourniquet application. If the target is to maintain postoperative cefuroxime concentrations above relevant MIC values, our results suggest that a second dose of cefuroxime should be administered at tourniquet release

Osteomyelitis caused by resistant bacterial strains can be dealt with antimicrobial agents which have a different mode of action compared to antibiotics. A very promising appears to be antimicrobial peptides (AMPs). We found and verified in vitro experiments that one of the most effective and least toxic antimicrobial peptides are contained in the wild bee venom. The aim of this study was to verify the efficacy of topically applied, synthetically prepared antimicrobial peptide (Hal 2/27) with carrier, originally isolated from the venom of the wild bee in experiments on laboratory rats. It was used 18 rats, which were indicated osteomyelitis of the left femurs. After a week of six rats were injected calcium phosphate carrier with AMP Hal 2/27, six rats received only a carrier without AMP and six other rats remained without further intervention. After a week, rats were sacrificed and X-ray was performed in all rats limbs. Rats who received carrier with AMP Hal 2/27 had less X-ray evidence of osteomyelitis of femurs compared to rats after administration of the carrier without AMP. Topical application of a new synthetic antimicrobial peptides isolated from wild bee venom (Hal 2/27) using local carriers seems to be a promising way to treat and prevent infectious complications in orthopedics and traumatology. Internal grant of University Hospital Motol, Advanced Therapies, NO: 9777 and Internal grant of University Hospital Motol, NO 6010

Honey has been used as a topical antiseptic for at least 5,000 years. SurgiHoney is a CE licensed sterile product, which has been proven to be non-toxic and effective when used topically in the treatment of chronically infected wounds. The key difference from other medical grade honey is the broad spectrum antimicrobial characteristics with activity against Gram +ve, Gram –ve and multi-resistant organisms. Its novel role against the bacterial bioburden and biofilm associated with periprosthetic infections around total knee arthroplasties (TKA's) is therefore considered. SurgiHoney was used as an implant coating immediately prior to wound closure after implantation of salvage endoprosthesis for multiply revised, infected TKA's undergoing staged reconstruction. We report a consecutive series of multi-revised, infected revision TKA's where SurgiHoney was used as an active antimicrobial coating. We discuss its intra-operative application and early clinical outcomes. The use of Surgihoney as a novel anti-microbial is established in the management of complex wound infections. This is the first reported use of SurgiHoney as a deep, implant coating in the salvage of prosthetic joint infection