Aim

Ciprofloxacin is recommended as anti-biofilm therapy for gram-negative periprosthetic joint infection. With ciprofloxacin monotherapy, resistance in gram-negative bacteria was observed. Therefore, we evaluated in vitro synergistic activity of fosfomycin, ciprofloxacin and gentamicin combinations against biofilms formed by E. coli and P. aeruginosa strains.

Aim. We aimed to assess the incidence and the outcome of Gram-negative prosthetic-joint infections (PJI) in 3 international tertiary hospital. Method. We included patients with Gram-negative PJI at Humanitas Clinical and Research Hospital (Milan, Italy), Centre Hospitalier Universitaire Vaudois (Lausanne, Switzerland) and Hospital Parc de Salut Mar (Barcelona, Spain) between 2014 and 2018 in a retrospective cohort. We described the treatment's success rate according to Gram-negative species and type of surgical procedure. Results. In the present cohort we have 780 PJI out of which 71 (9.1%) were caused by Gram-negative bacteria (polymicrobial infection 30%, Escherichia coli 25%, Pseudomonas aeruginosa 20%, Proteus spp. 4%, Klebsiella spp. 3%, Morganella morganii 3%, Enterobacter 3%, others 12%). Gram-negative PJI were more common in females (60%) than males (40%). Sixty percent had a hip infection, 40% a knee infection, the median age was 74 years and the median ASA score was 3. It was a chronic infection in 60% of the cases and an acute one in 40%. Two-step exchange was performed in 55%, débridement and retention (DAIR) in 30%, one-step exchange in 11% and implant removal without replacement in 4% of the patients. The overall treatment success rate was 89%. The success rate was better for two-step exchange (95%) compared to DAIR (81%) and one-step exchange (87%) (p=0.068). The median antibiotic duration was 68 days and ciprofloxacin was used in 70% of the cured patients versus in 88% of the failures (p=0.388). Infections caused by Escherichia coli were associated with a lower success rate (83%) especially compared to Pseudomonas aeruginosa (93%) and polymicrobial infections (90%) (p=0.358). Finally, the success rate was better in knee PJI compared to hip PJI (97% versus 83%, p=0.121) and in females compared to males (93% versus 82%, p=0.121). Conclusions. The treatment's success of Gram-negative PJI is comparable to reported rates for all bacteria. However, our results suggest that surgical management with two-step exchange might be useful in selected patients’ groups such as those with Escherichia coli PJI. Moreover, ciprofloxacin use seems not to improve cure rate

Hypochlorous acid (HOCl) is a potent anti-bacterial agent which could reduce periprosthetic joint infection. Early infection complications in joint replacements are often considered to be due to local contamination at the time of surgery and result in a significant socioeconomic cost. Current theatre cleaning procedures produce “clean” operating theatres which still contain bacteria (colony forming units, CFU). Reducing this bacterial load may reduce local contamination at the time of surgery. HOCl is produced naturally in the human neutrophil and has been implicated as the primary agent involved in bacterial killing during this process. In vitro research confirms its efficacy against essentially all clinically relevant bacteria. The recent advent of commercial production of HOCl, delivered as a fog, has resulted in extensive use in the food industry. Reported lack of corrosion and high anti-bacterial potency are seen as two key factors for the use of HOCl in the orthopaedic environment. Prior work by the authors comparing human cell toxicity of HOCl, chlorhexidine and iodine solutions shows favourable results. This study evaluates use of neutral HOCl applied as a dry room fog to decrease bacteria in the operating theatre environment. Using an animal operating theatre as the test site, bacterial swabs were taken from ten 100cm. 2. sample areas before standard cleaning with detergent, after standard cleaning, and again after 60 minutes exposure to HOCl fog. After standard cleaning, 6 of 10 sample sites recorded significant bacterial growth (>10 CFU/100cm. 2. ). After exposure to HOCl fog, growth in all 10 sites was below detection limits (<10 CFU/100cm. 2. ). This was repeated with specific exposure to Staphylococcus aureus and Escherichia coli. We can conclude that HOCl is effective when used as a fogging agent to reduce bacterial loading within an operating theatre environment and as such has significant potential to reduce intraoperative contamination and periprosthetic infection

Aim. Currently, gram-negative bacteria (GNB), including multidrug-resistant (MDR-GNB) pathogens, are gaining importance in the aetiology of prosthetic joint infection (PJI). To characterize the antimicrobial resistance patterns of Gram-negative bacteria (GNB) causing hip prosthetic joint infections in elderly patients treated at a Brazilian tertiary academic hospital. Method. This is a retrospective, cross-sectional study of patients over 60 years of age undergoing hip arthroplasty from 2018 to 2023 at a tertiary academic trauma, which were diagnosed with hip prosthetic joint infection. PJI diagnosed was based on EBJIS criteria, in which intraoperative tissue cultures identified the pathogens. Demographics, reason for arthroplasty, type of implant and susceptibility patterns using disk diffusion method were analysed. Results. Overall, among 17 elderly patients diagnosed with hip infected arthroplasty, 45 bacterial isolated were identified. Debridement, irrigation, antibiotic and implant retention (DAIR) procedures due to uncontrolled infection occurred in 47.0% (n=8/17), and five patients underwent more than two DAIR surgeries. Tissue cultures yielded eleven different bacterial species, with GNB accounted for 64.4% (n=29/45) of pathogens. Klebsiella pneumoniae, Acinetobacter baumannii, Escherichia coli, and Pseudomonas aeruginosa were identified in 34.5% (n=10/29), 17.25% (n=5/29), 13.8% (n=4/29), and 13.8% (n=4/29), respectively. In the resistance profile analysis, E. coli was most sensitive to antibiotics, whereas K. pneumoniae showed resistance rates higher than 70% for cephalosporins, carbapenems, and quinolones. All A. baumannii isolates were resistant to meropenem, and 80% of these isolates were resistant to amikacin. Conclusions. This study emphasizes the role of GNB in the microbiological profile of PJI among elderly patients at a tertiary hospital in a Brazilian centre. The present study portrays a worryingly higher rates of MDR-GNB, mainly to quinolones and cephalosporins resistance which have been the cornerstone of PJI antibiotic treatment. In addition, higher rates carbapenems and aminoglycosides resistance shows a threat to antibiotic treatment of PJI. More global studies need to be carried out to show a likely change in the microbial epidemiology of PJI

Aim. Prosthetic joint infections pose a major clinical challenge. Developing novel material surface technologies for orthopedic implants that prevent bacterial adhesion and biofilm formation is essential. Antimicrobial coatings applicable to articulating implant surfaces are limited, due to the articulation mechanics inducing wear, coating degradation, and toxic particle release. Noble metals are known for their antimicrobial activity and high mechanical strength and could be a viable coating alternative for orthopaedic implants [1]. In this study, the potential of thin platinum-based metal alloy coatings was developed, characterized, and tested on cytotoxicity and antibacterial properties. Method. Three platinum-based metal alloy coatings were sputter-coated on medical-grade polished titanium discs. The coatings were characterized using optical topography and scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS). Ion release was measured using inductively coupled plasma optical emission spectrometry (ICP-OES). Cytotoxicity was tested according to ISO10993-5 using mouse fibroblasts (cell lines L929 and 3T3). Antibacterial surface activity, bacterial adhesion, bacterial proliferation, and biofilm formation were tested with gram-positive Staphylococcus aureus ATCC 25923 and gram-negative Escherichia coli ATCC 25922. Colony forming unit (CFU) counts, live-dead fluorescence staining, and SEM-EDS images were used to assess antibacterial activity. Results. Three different platinum-based metal alloys consisting of platinum-iridium, platinum-copper, and platinum-zirconium. The coatings were found 80 nm thick, smooth (roughness average < 60 nm), and non-toxic. The platinum-copper coating showed a CFU reduction larger than one logarithm in adherent bacteria compared to uncoated titanium. The other coatings showed a smaller reduction. This data was confirmed by SEM and live-dead fluorescence images, and accordingly, ICP-OES measurements showed low levels of metal ion release from the coatings. Conclusions. The platinum-copper coating showed low anti-adhesion properties, even with extremely low metal ions released. These platinum-based metal alloy coatings cannot be classified as antimicrobial yet. Further optimization of the coating composition to induce a higher ion release based on the galvanic principle is required and copper looks most promising as the antimicrobial compound of choice. Acknowledgments. This publication is supported by the DARTBAC project (with project number NWA.1292.19.354) of the research program NWA-ORC which is (partly) financed by the Dutch Research Council (NWO); and the AMBITION project (with project number NSP20–1-302), co-funded by the PPP Allowance made available by Health-Holland, Top Sector Life Sciences & Health to ReumaNederland

Aim. The primary objective is to evaluate the diagnostic performance of inoculating homogenized tissue and bone biopsies in blood culture bottles (BCB) for patients with (suspected) orthopaedic device-related infections. As secondary objective the time to positivity (TTP) of BCB and Wilkins-Chalgren broth (conventional method) will be evaluated. Method. Patients undergoing revision surgery due to suspected or proven fracture-related infection (FRI) or periprosthetic joint infection (PJI) according to respectively Consensus definition and EBJIS definition are included. 1,2. A minimal of three macroscopic infected/inflamed tissue/bone samples are collected in a container with saline and glass beads. 1.5 mL of the homogenized suspension is inoculated in BacT/ALERT FA and FN Plus bottles for 14 days. The remaining suspension is inoculated in Wilkins-Chalgren broth for 10 days and subcultured when cloudy or after 10 days. TTP is defined as the time until definite identification of the pathogen in the Laboratory Information System. Results. Up to now, 25 patients have been included, 11 (44%) had concordant results in BCB and the CM. In 11 patients cultures showed negative results for both methods. Three patients tested positive with BCB but remained negative with the same pathogen in CM. In the first patient, the CM failed to identify anaerobic bacteria (i.e. Fusobacterium nucleatum). In the second patient, three BCB were positive with Staphylococcus capitis. The third patient showed an infection with Escherichia coli, which was detected in all samples from the BCB, while all cultures obtained with the CM remained negative. A possible explanation for this discrepancy could be that this patient already received antibiotic therapy. BCB contain resins, which are capable of neutralizing antibiotic activity. Another case illustrating superiority of BCB involved an infection with Cutibacterium acnes, which showed positivity in six BCB, while only three were positive using the CM. We observed the shortest TTP with BCB. The median TTP of BCB was 32.0 hours (IQR 29.8) compared to a median TTP of 77.5 hours (IQR 107.6) when culturing with the CM. Contamination was seen in three patients with both methods, in eight patients contamination was only seen with the CM. For the remaining 14 patients no contamination was found. Conclusions. The results in this ongoing study indicate that the recovery of pathogens and TTP is better using BCB compared to CM. In addition, contamination occurs less frequently with the BCB method. Culturing tissue or bone biopsies in BCB seems a promising and faster detection method

Aim. Antibacterial activity of coatings based on metal and metal oxide nanoparticles (NPs) often depends on materials and biotic targets resulting in a material-specific killing activity of selected Gram-positive and Gram-negative bacteria, including drug-resistant strains. In this perspective, the NPs loading amount, the relative elemental concentration inside the nanogranular building blocks and the deposition method are of paramount importance when the goal is to widen the antimicrobial spectrum, but at the same time to avoid high levels of metal content to limit undesired toxic effects. Aim of the present study was evaluation of the antimicrobial properties of two multielement nanogranular coatings composed of Titanium-Silver and Copper and of Magnesium-Silver and Copper. Method. Ti-Ag-Cu and Mg-Ag-Cu NPs were deposited on circular cover glasses (VWR) by Supersonic Cluster Beam Deposition. Biofilm-producer strains of Staphylococcus aureus (methicillin susceptible and resistant), Staphylococcus epidermidis (methicillin susceptible and resistant), Escherichia coli (fully susceptible and producer of extended spectrum beta lactamases), and Pseudomonas aeruginosa (susceptible and multidrug-resistant) were selected. The abilities of the selected strains to adhere, colonize and produce biofilm on the discs coated with Ti-Ag-Cu or Mg-Ag-Cu NPs were compared to uncoated circular cover glasses which were used as growth control. Cytotoxicity was also evaluated in order to assess the biocompatibility of the newly synthesized NPs. Results. In comparison to uncoated controls, both coatings showed significant anti-adhesive properties against S. aureus, S. epidermidis, and E. coli. Reduction in adhesion to Mg-Ag-Cu coated discs was observed also for P. aeruginosa isolates, although differences vs uncoated controls did not reach statistical significance. Biofilm formation was reduced on discs coated with Mg-Ag-Cu compared to Ti-Ag-Cu and, again, coatings had a milder effect on P. aeruginosa, probably due to its exceptional capability of attachment and matrix production. These results were confirmed by the evaluation of bacterial colonization on nanoparticles-coated discs by means of confocal laser scanning microscopy. A viability of 95.8% and 89.4% of cells cultured in the presence of Ti-Ag-Cu and Mg-Ag-Cu discs, respectively, when compared to negative controls was observed, thus excluding cytotoxic effects on eukaryotic cells. Conclusions. The newly synthesized Ti-Ag-Cu and Mg-Ag-Cu coatings are able to limit bacterial adhesion colonization and biofilm production, thus highlighting the safe use of multi-element families of NPs as new strategies against bacterial attachment to the surface of biomedical implants. However, further studies addressing activity against P. aeruginosa and including a wide number of isolates are warranted

Aim. The efficacy of various irrigation solutions in removing microbial contamination of a surgical wound and reducing the rate of subsequent surgical site infection (SSI), has been demonstrated extensively. However, it is not known if irrigation solutions have any activity against established biofilm. This issue is pertinent as successful management of patients with periprosthetic joint infection (PJI) includes the ability to remove biofilm established on the surface of implants and necrotic tissues. The purpose of this study was to evaluate the efficacy of various irrigation solutions in eradicating established biofilm, as opposed to planktonic bacteria, in a validated in vitro model. Method. Established biofilms of Staphylococcus aureus and Escherichia coli were exposed to different irrigation solutions that included Polymyxin 500,000U/L plus bacitracin 50,000U/L, Vancomycin 1g/L, Gentamicin 80mg/L, Normal saline 0.9%, off-the-shelf Betadine 0.3%, Chlorhexidine 0.05%, Benzalkonium 1.3g/L, Sodium hypochlorite 0.125%, and Povidone-iodine 0.5%. Each experiment was conducted in a 96-well microtiter plate with a peg lid and standardized per the MBEC assay manufacturer's protocol. Following 2 minutes of solution exposure to the irrigation solution, residual biofilms were recovered by sonication. Outcome measures for antibiofilm efficacy were residual colony forming units (CFU) and optical density (690nm). Experiments were conducted in 24 replicates and the observations recorded by two blinded observers. Statistical analysis involved t-tests with Bonferonni adjustment. Results. Povidone-iodine 0.5%, Betadine 0.3%, Benzalkonium 1.3g/L, and Sodium hypochlorite 0.125% were significantly more efficacious against S.aureus biofilm versus all other solutions (p<0.001). Against E.coli biofilm, Povidone-iodine-0.5%, Benzalkonium-1.3g/L and Sodium hypochlorite-0.125% were also most effective compared to other irrigation solutions (p<0.001). Polymyxin-bacitracin, Gentamicin, Vancomycin, and Saline solutions had minimal activity against both E.coli and S.aureus biofilms (p<0.001). Similar trends were observed using both experimental endpoints (CFU and Turbidity) and both investigators (interrater reliability; r=0.99). Conclusion. This in vitro study observed that topical antibiotic solutions do not have any activity against established biofilms. Irrigations solutions containing adequate amount of povidone-iodine, betadine, sodium hypochlorite, and benzalkonium appear to have activity against established biofilm by gram positive and gram negative organisms. The use of these irrigation solutions may need to be considered in patients with established PJI

Aim. Bone and joint infections are frequent in African countries and their prevention and treatment remain a great challenge. This study aimed to determine the bacterial ecology and sensitivity of isolates to locally available antibiotics in orthopedic unit of a tertiary care hospital in Cameroun. Method. During a 12 months period, all the patients presenting with osteomyelitis or septic arthritis irrespective of the mechanism and the location were enrolled in this study. Intraoperative samples (biopsies) were taken and sent for microbiological analysis, and all strains isolated were tested for antibiotic sensitivity according to conventional methods. Results. on the 52 bacteriological analysis performed, 48 were positive. The most isolated germs were staphylococcus aureus (41.9 % of isolates), pseudomonas aeruginosa (14.5 %), Escherichia coli (14.5 %) and Klebsiella pneumonia (12.9 %). The antibiotic sensitivity pattern revealed worrying resistance rates for common and affordable antibiotics: ampicillin (94 %), amoxicillin + clavulanic acid (63.9 %), ceftazidim (65.5%), ticarcillin + clavulanate (57.4%), gentamycin (49 %), ciprofloxacin (40 %), cefuroxim (40 %), tobramycin (38.5 %). The strains of Staphylococcus aureus showed resistance to penicillin G (83%), oxacillin (25%), lincomycin (27%) and vancomycin (7%). The overall highest sensitivity rates were observed with amikacin (92 %) and imipenem (90.1%), which for many patients were the only effective locally available antibiotics. The daily cost of treatment with those two antibiotics is close to the guaranteed minimum wage in our country. Conclusions. The alarming rate of multidrug-resistant bacteria makes the long antibiotic treatment of bone infections unaffordable (in a context of lack of social insurance) for most of our patients. We advocate strong national policies for bacteriological surveillance and antibiotic misuse de-escalation to prevent antibiotic resistance

Aim. Phage therapy has attracted attention as a promising alternative treatment option for biofilm infections. To establish a successful phage therapy, a comprehensive stock of different phages covering a broad bacterial spectrum is crucial. We screened human and environmental sources for presence of lytic phages against selected bacteria. Methods. Saliva collected from 10 volunteers and 500 ml of sewage water were screened for the presence of lytic phages active against 20 clinical strains of Staphylococcus aureus and 10 of Escherichia coli, both isolated from patients with prosthetic joint infection. Laboratory strains of methicillin-resistant S. aureus (MRSA)*1 and E. coli*2 were also tested. Screening was performed plaque-assay to detect phages for different strains. Isolated plaques were collected and phages were enriched to determine their activity against their bacterial host strains. The activity of bacteriophages against adherent E. coli and MRSA was evaluated by crystal violet, staining bacterial biofilms grown on glass beads. Results. Six bacteriophages specific for MRSA were isolated from saliva. Bacteriophages for E. coli strains were isolated from sewage water (n=3) and saliva (n=1). All bacteriophages tested against biofilms of their bacterial host showed a reduction of the total biomass (ranging from 19% to 84%). Conclusions. Both sewage and saliva samples provided bacteriophages specific against selected bacterial strains. 24h phage treatment of E. coli and S. aureus biofilms lead to a reduction but not to a complete eradication of biofilm

Aim. Prosthetic joint infections (PJI) due to Enterobacter cloacae are rare and often severe. The aim of this study is to describe cases with E. cloacae PJI. Method. We conducted a retrospective and a monocentric study in an orthopedic unit where complex bone and joint infections are managed. From 2012 to 2016, we included patients with PJI which perioperative samples were positive with E. cloacae. We collected background, clinical, biological and microbiological data of the current infection, surgical and medical treatment, and the outcome of these patients. Results. A total of twenty patients were included which 8 were male. Location was hip in 14 cases, knee in 5 cases and ankle in one case. The median time between arthroplasty and revision for infection was 3 years. Fourteen patients had at least two surgeries for previous PJI. The median time between the last surgery and the revision for E. cloacae infection was 31 days. Eleven patients were infected by extended-spectrum beta-lactamases (ESBL) strains. Most frequently, the antibiotics used were carbapenem in 9 cases, cefepim in 7 cases, a quinolone in 7 cases and fosfomycin in 4 cases. Infection was cured in 10 cases (50%) with a median time of follow-up of 24 months. Five patients had a recurrent infection, three due to Staphylococcus epidermidis, one to Staphylococcus epidermidis and Propionibacterium acnes and one to Escherichia coli. Four patients had a relapse of E. cloacae infection. One patient died from non-infectious cause (stroke). Conclusions. PJI infections due to E.cloacae usually occur early after the last prosthetic surgery, typically in patients with complex surgical history. A poor outcome, observed in nearly half of the patients could be explained in part by an association of factors: multiple risks factors, complex infectious history, a high rate of multiple resistance to antibiotics, unfavorable skin conditions

Aim. We used a polymerase chain reaction (PCR) lateral flow assay1) to rapidly diagnose joint infection. We evaluated the usefulness of multiplex-PCR (PCR lateral flow assay: PCR-LF) using detailed clinical data. Method. A total of 35 synovial fluid samples were collected from 26 patients in whom bacterial infection was suspected, including 22 from knee joints, 11 from hip joints, and 2 from other joints. After purifying the DNA from the samples, multiplex PCR targeting two MRSA-associated genes (femA and mecA) and the bacterial 16S rRNA gene was performed. Amplified gene fragments were specifically detected with DNA probes immobilized on stick devices through DNA-DNA hybridization and visualization, enabling diagnosis of MRSA, MSSA, MRCNS, gram-positive, and/or gram-negative bacterial infection. Genetic identification of bacteria by determining the 16S rRNA gene sequence was also performed using multiplex PCR-positive samples. Finally, the usefulness of our PCR-LF method was evaluated using detailed clinical data. Results. The results of PCR-LF were 9 gram-positive and 1 gram-negative bacterial infections. Eleven bacterial species were identified based on 16S rRNA gene sequences. Ten (90.9%)of the eleven samples (bacterial species) were identified using our PCR-LF. Five samples were detected in bacterial cultures; two are MSSA, one is Streptococcus agalactiae, one is Escherichia coli, one is Prevotella oralis. We diagnosed 6 samples as clinical infections. Therefore, the sensitivity and specificity of the culture tests were 83% and 100%, respectively, while for PCR-LF, these values were 83% and 83%. Conclusions. PCR-LF is highly sensitive and effective for the rapid diagnosis of joint infection; however, dead bacteria may also be detected. Moreover, because the target bacterial species are limited, clinical diagnosis based on the results of multiple examinations is necessary

Aim. Gram-negative aerobic bacteria account for 10%-17% of periprosthetic joint infection (PJI). Due to its biofilm-activity, ciprofloxacin plays a key role in the treatment of gram-negative PJI. However, data about treatment outcome of these infections are conflicting. With this retrospective study we aim at evaluating characteristics and outcome of gram-negative PJI. Method. We retrospectively included consecutive patients with gram-negative PJI treated at our institution from 01/2013 to 03/2018. Diagnosis of PJI was defined by the proposed European Bone and Joint Infection Society (EBJIS) criteria. Growth of gram-negative aerobic bacteria was required in synovial fluid, periprosthetic tissue or sonication fluid. Clinical success (infection-free status) was defined as fulfillment of all of the following criteria: (i) unremarkable surgical site and no subsequent surgery (ii) no PJI related mortality and (iii) no long-term antimicrobial suppression therapy of >6 months. Results. A total of 76 patients with gram-negative PJI involving 45 hips, 26 knees, 3 elbows and 2 shoulders were analyzed. The median patient age was 76 years (range, 41–92 years). The route of infection was perioperative in 52 cases, hematogenous in 17 cases and contiguous in 5 cases. The most common isolated pathogens were Escherichia coli (n=31), Klebsiella species (n=17), Proteus species (n=13), Enterobacter species (n=11) and Pseudomonas aeruginosa (n=9). Ciprofloxacin resistance was detected in 20 of 90 (23%) gram-negative pathogens. 21 patients were treated with two-stage revision, 17 with prosthesis retention, 16 with permanent prosthesis removal, 14 with multi-stage exchange and 6 with one-stage revision. In 55 of 71 (77%) patients, ciprofloxacin was included in the treatment regimen. Median follow-up was 10.8 months (range, 1.6–60.7 months) and infection was eradicated in 29 of 47 patients (62%). Among 18 failures, 13 (72%) experienced a new PJI due to another pathogen (n=11) or had negative cultures (n=2), one patient died. The failures occurred after a median of 13.3 months (range, 3.9–28.8 months). All 4 patients with relapse caused by the same pathogen were resistant to ciprofloxacin. Ciprofloxacin-resistance was associated with worse outcome compared to ciprofloxacin-susceptible bacteria (5/13 (38%) vs. 23/33 (70%), p=0.09). Conclusions. The overall outcome of gram-negative PJI was poor (62%). However, most infections were caused by a new pathogen or were culture-negative and occurred after 13.3 months. Ciprofloxacin resistance of the causative pathogen was associated with treatment failure. The reason for the high rate of new PJI is unclear and should be meticulously investigated to improve the outcome

Aim. Revision surgery and debridement and implant retention are recognised approaches for managing prosthetic joint infections (PJI) but may not always be indicated. If the patient is unable to have or declines surgery, prolonged suppressive antibiotic therapy (PSAT) is an option. This study aims to define outcomes of PSAT from a single unit. Method. A retrospective study was performed. All cases of PJI involving the hip or knee between 2012 and 2017 were identified from our institutional database and cross referenced with patient notes. One hundred and seventy eight cases were identified. Of these, 23 (12.9%) (10 hips, 13 knees) were treated with PSAT. Infection was diagnosed based on the MSIS criteria in all cases and all cases were managed by a multidisciplinary team which included specialist microbiologists. One case of long term antifungal therapy was additionally identified. Co-morbidity was assessed using the Charlson co-morbidity index. Exacerbations of infection and need for further surgery were recorded. Results. The mean age was 72 years (Range 35–93 years). The mean Charlson-score was 4.3 (range 1–7). Mean follow up was 24 months (Range 1–54 months). Antibiotics were commenced within 3 months of surgery in 20 cases and between 2 and 4 year following surgery in the remainder. Prolonged antibiotic therapy followed debridement and implant retention in 12 cases, single stage revision in 4 cases and 2 stage revisions in 3 cases. The average number of surgical procedures undergone by each patient prior to starting antibiotic suppression therapy was 1.8 (Range 1–4 procedures). Staphylococcal species were isolated in 13 cases (MRSA 1, MSSA 5, Staph. Epidermidis 5, CONS 1, Staph Pasteuri 1). Escherichia Coli and Streptococci were isolated in 2 cases each. Four cases were due to polymicrobial infection. No organisms were identified in 2 cases. Candida Albicans was identified in 1 case. All cases of infection were treated with prolonged oral antibiotics. Twenty patients (87%) received 6 weeks of intravenous antibiotics prior to commencing prolonged oral antibiotics. Two patients experienced persistent symptoms and required amputation (both TKA). One immunocompromised patient required admission for sepsis related to their infected TKA. The success rate of long term suppressive antibiotics was 87% (20/23) successful at an average 2 year follow up. There was persistent wound discharge in 1 case (4.3%). Conclusions. Prolonged suppressive antibiotic therapy is an effective option for management of PJI and related symptoms with a low incidence of complications in surgically resistant PJI

Aim. Prosthetic joint infections (PJI) are devastating complications after hip arthroplasty and infection rates varies internationally between 0.76% to 1.24%. Hemi-arthroplasty (HA) is the gold standard treatment for dislocated femoral neck fractures. Recently, total hip arthroplasty (THA) has been suggested to generate even better outcomes. However, little is known about PJIs after hip fractures. The purpose of this study was to investigate PJIs after femoral neck fracture in a population-based sample. Methods. Clinical databases were harvested for all THA or HA procedures done for the treatment of femoral neck fractures at our hospital district (HUS) of 1.6 million inhabitants. Altogether, 3693 arthroplasty procedures for hip fractures were performed between 2011 to 2015. The original patient records of each case were reviewed. Complication(s) leading to readmission(s), the microbe(s), and the treatment protocol of each infection was recorded until the closing date (31.12.2016). The definition of PJI according to Musculosceletal Infection Society modified at the International Consensus meeting was used. Results. We detected 111 infections (10 THAs;101 HAs):42 superficial infections (1.1%) and 69 PJIs (1.9%). The PJI rate after THA was 3.7% (8/219) and 1.8% after HA (61/3474) (p=0.04;OR 2.12, 95%CI 1.00–4.49). Most PJIs in THA group (6/8) were treated by debridement, antimicrobials, and implant retention (DAIR) and two by 2-stage exchange. In the HA group the DAIR was the first surgical treatment for 51 PJIs (84%). Other treatment options used were girdlestone (n=3), one-stage exchange (n=2), lavation (n=2), and conservative treatment (n=3). The bacteria cultured at THA group were: Staphylococcus epidermidis (n=4), Staphylococcus aureus (n=3), Streptococcus agalactiae (n=2), and Staphylococcus haemolyticus and at the HA group Staphylococcus aureus (n=25, including 1 MRSA), Staphylococcus epidermidis (n=11), other coagulase negative staphylococci (n=7), Pseudomonas aeruginosa (n=6), Enterococcus faecalis (n=6), Escherichia coli (n=2), and streptococci (n=2). Multiple bacteria were cultured from seven PJIs. The causative microbe was unknown in five PJIs. Conclusion. THA patients had higher rate of PJIs compared to HA, however, the small sample size of the THA group may limit the statistical power of this study. The PJIs after hip fractures were usually treated by DAIR, which is also main PJI treatment after elective THAs. The overall PJI rate was higher among hip fracture than after elective THAs in the literature. The existing trend of treating more dislocated hip fractures with THA may thus lead to increased rated of PJIs in the future

Aim. To investigate the antimicrobial activity of a gentamicin-loaded bone graft substitute (GLBGS) in the prevention and eradication of bacterial biofilms associated with prosthetic joint infections (PJI). Method. The GLBGS (17,5 mg gentamicin/ml paste) with 40% hydroxyapatite/60% calcium sulfate. 1. was tested against biofilms of methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300, methicillin-susceptible S. aureus (MSSA) ATCC 29213, Escherichia coli Bj HDE-1, S. epidermidis ATCC 12228 and Enterococcus faecalis ATCC 19433. For prevention studies, glass beads and different combinations of GLBGS were co-incubated for 24h at 37°C in CAMH broth with 1–5 × 10. 6. CFU/mL of bacteria. For eradication, biofilms were formed on glass beads for 24h at 37°C in CAMH broth. Then, beads were incubated with different combinations of GLBGS in medium at 37°C for 24h. For microcalorimetric measurements, beads were placed in ampoules and heat flow (µW) and total heat (J) were measured at 37°C for 24h. The minimal heat inhibitory concentration (MHIC) was defined as the lowest gentamicin concentration reducing the heat flow peak by ≥90% at 24h. Results. The GLBGS showed a good activity against all tested strains in both biofilm prevention and eradication. All MHIC values are reported in Table 1. Lower MHICs were observed when GLBGS was tested against E. coli (9.6 µg/mL prevention and 19.2 µg/mL eradication) and S. epidermidis (86 µg/mL and 38.8 µg/mL, respectively). For both prevention and eradication of MSSA, GLBGS MHIC was 631 µg/mL. E. faecalis biofilm formation was prevented with 631 µg/mL and eradicated with double concentration. MRSA showed a higher resistance to GLBGS up to 2516 µg/mL, both in biofilm prevention and eradication. Conclusions. This GLBGS is a valid composite for the prophylaxis and treatment of PJI. Further studies will be performed to evaluate the activity of higher concentrations of GLBGS against MRSA. 1. CERAMENT™|G, BONESUPPORT AB, Sweden

This study aimed to determine the optimal formulation of antibiotic-loaded bone cement (ALBC) for periprosthetic joint infection (PJI) using both in vitro and in vivo models incorporating various combinations of gram-positive and gram-negative antibiotics. The in vitro antibiotic release characteristics and antibacterial capacities of ALBCs loaded with either 4 g of vancomycin or teicoplanin and 4 g of ceftazidime, imipenem, or aztreonam were measured against methicillin-susceptible S. aureus, methicillin-resistant S. aureus, coagulase-negative staphylococci, Pseudomonas aeruginosa and Escherichia coli. ALBC spacers with superior in vitro antibacterial capacity were then implanted into ten patients (five females and five males between 29 and 75 years of age) diagnosed with chronic hip/knee PJIs and antibacterial activities within joint fluid were measured. The average duration of ALBC spacer implantation was 80 days (range, 36–155 days). Antibiotic concentrations and antibacterial activities of joint fluid at the site of infection were measured during the initial period as well as several months following spacer implantation. Cement samples loaded with vancomycin/ceftazidime or teicoplanin/ceftazidime exhibited equal or longer antibacterial duration against test bacteria as compared with other ALBCs. Joint fluid samples exhibited antibacterial activity against the test microorganisms including ATCC strains and clinically isolated strains. There were no adverse systemic effects, infection at second stage re-implantation, or recurrent infection at final follow-up. Vancomycin/ceftazidime ALBC provided broad antibacterial capacity both in vitro and in vivo and was shown to be an effective and safe therapeutic measure in the treatment of hip/knee PJIs. We thank H.Y. Hsu for performing bioassay

Introduction. The use of irrigation solution during surgical procedures is a common and effective practice in reduction of bioburden and the risk of subsequent infection. The optimal irrigation solution to accomplish this feat remains unknown. Many surgeons commonly add topical antibiotics to irrigation solutions assuming this has topical effect and eliminates bacteria. The latter reasoning has never been proven. In fact a few prior studies suggest addition of antibiotics to irrigation solution confers no added benefit. Furthermore, this practice adds to cost, has the potential for anaphylactic reactions, and may also contribute to the emergence of antimicrobial resistance. We therefore sought to compare the antimicrobial efficacy and cytotoxicity of irrigation solution containing polymyxin-bacitracin versus other commonly used irrigation solutions. Methods. Using two in vitro breakpoint assays of Staphylococcus aureus (ATCC#25923) and Escherichia coli (ATCC#25922), we examined the efficacy of a panel of irrigation solutions containing topical antibiotics (500,000U/L Polymyxin-Bacitracin 50,000U/L; Vancomycin 1g/L; Gentamicin 80mg/L), as well as commonly used irrigation solutions (Normal saline 0.9%; Povidone-iodine 0.3%; Chlorhexidine 0.05%; Castile soap 0.45%; and Sodium hypochlorite 0.125%) following 1 minute and 3 minutes of exposure. Surviving bacteria were counted in triplicate experiments. Failure to eradicate all bacteria was considered to be “not effective” for that respective solution and exposure time. Cytotoxicity analysis in human fibroblast, osteoblast, and chrondrocyte cells exposed to each of the respective irrigation solutions was performed by visualization of cell structure, lactate dehydrogenase (LDH) activity and evaluation of vital cells. Toxicity was quantified by determination of LDH release (ELISA % absorbance; with higher percentage considered a surrogate for cytotoxicity). Descriptive statistics were used to present means and standard deviation of triplicate experimental runs. Results. Polymyxin-Bacitracin, Saline and Castile soap irrigation at both exposure times were not effective at eradicating S aureus or E coli (Figure 1). In contrast, Povidone-iodine, Chlorhexidine, and Sodium hypochlorite irrigation were effective at eradicating both S aureus and E coli. Vancomycin irrigation was effective at S aureus eradication but not against E coli, whereas Gentamicin irrigation showed partial efficacy against E coli eradication but none against S aureus. The greatest cytotoxicity was seen with Chlorhexidine (49.4% ± 1.9). This was followed by Castile soap (33.2% ±3.9), Vancomycin (9.01% ±5.1), Polymyxin-Bacitracin (8.45% ±1.5), and Gentamicin irrigation (4.72% ±2.3) (Figure 2 and Figure 3 microscopy images). Povidone-iodine and Sodium hypochlorite showed least cytotoxicity (0.05% ±0.08 and 0.11%±0.19, respectively). Similar trends were seen at both exposure times and across fibroblasts, osteoblasts and chondrocytes. Discussion. This in vitro study suggests that addition of polymyxin-bacitracin to saline irrigation solution is a futile exercise. Taken within the context of its associated expense, risk of hypersensitivity and impact upon antimicrobial resistance, our findings bring its widespread clinical usage into question. Povidone-iodine may be a more effective option, with a more favorable cytotoxicity profile than the other commonly used irrigation solutions. Clinical outcomes should be studied to determine the most effective agent, concentration, and exposure time for intraoperative irrigation

Revision surgery and surgery in previously operated areas are associated with an increased infection risk. In such situations, aggressive surgical debridement may be necessary to control and eradicate the infection. Full thickness defects resulting from such debridement present as a challenge. In most cases, an association of various methods, both surgical and non-surgical, is necessary. Our goal is to describe the use of vaccum dressings as an effective way to deal with extensive and infected dorsolumbar surgical defects, while avoiding the use of myocutaneous flaps. This is a retrospective and descriptive case report based on data from clinical records, patient observation and analysis of complementary exams. We present the case of a 57-years-old obese woman with prior history of double approach with posterior instrumentation and spine arthrodesis (D3 to L4) due to severe dorsolumbar adolescent idiopathic scoliosis. She presented to our consult 42 years after surgery, complaining of lower back pain. Clinical observation and imaging exams demonstrated degenerative disc disease in L5-S1 and L5 anterolisthesis. There was also distal instrumentation breakage (right L4 pedicular screw and contralateral rod) with pseudarthrosis suspicion. Distal instrumentation was removed and no pseudarthrosis was found. Therefore, posterior instrumentation and arthrodesis was performed, from L4 to S1. Surgery went without complications. One week after surgery, patient developed fever and inflammatory signs at the surgical incision, with purulent oozing. Escherichia coli and Proteus mirabilis were identified as the causative agents. Decision was made to remove both lumbar and distal dorsal instrumentation and perform aggressive debridement and lavage, with debridement surgery being repeated twice. Finally, a full thickness defect with approximately 20cm long and 6cm wide resulted from the debridement. A vacuum dressing was then applied, for 5 weeks, with progressive decrease in clinical and analytical inflammatory parameters and wound closure. Four months after the initial surgery, patient was discharged with complete defect closure and reepithelialization. This dressing technique provided a sound solution for defect resolution, as well as an important aid for infection control. It proved to be a viable option in an extensive defect, when surgical flap techniques and traditional dressing techniques could not provide a complete solution

Correct diagnosis of infection is crucial for an adequate treatment of orthopedic implant-related infections. In the orthopedic field, infections can be difficult to diagnose(1). As a consequence, patients may suffer from an undiagnosed and untreated implant-related infection. To solve this problem, we are searching for a diagnostic method to detect these so-called low-grade infections. The technique fluorescence in situ hybridization (FISH) can detect slow-growing and even dead bacteria. Further, as FISH results are available within an hour after tissue collection it is an ideal candidate for diagnostic purposes. AIM: to evaluate the FISH technique for its potential to detect and identify orthopedic infections. Sonication fluid (SF) was collected by sonicating retrieved implants(2) from 62 patients. All samples were subjected to bacterial culture for clinical diagnostics. In addition, a commercially available FISH kit (miacom diagnostics, Germany), specifically designed for blood analysis (hemoFISH Masterpanel), was used. The kit contained 16S rRNA probes (positive control), non-sense probes (negative control), probes for Staphylococcus spp., Staphylococcus aureus, Streptococcus spp., Streptococcus pneumoniae, Streptococcus agalactiae, Enterococcus faecium, Enterococcus faecalis, Enterobacteriaceae, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Acetinobacter spp., and Stenotrophomonas maltophilia. All FISH analyses were performed according to the protocol provided with the kit. Culture and FISH results were compared, considering culture as the gold standard. Culture resulted in 27 positive and 35 negative samples. Comparing FISH (16S rRNA probe) with culture, 24 samples tested true-positive and 32 samples true-negative. Furthermore, 3 samples tested false-negative and 3 samples false-positive. The species cultured with the highest incidence were Propionibacterium acnes and Staphylococcus epidermidis, both from 8 SF samples. As the kit did not contain a probe for Propionibacterium acnes, these strains were only detected by the 16S rRNA probe. In addition, the latter samples tested positive with the Staphylococcus spp. probe. Interestingly, 3 samples tested positive with FISH that were culture negative. This result could indicate a higher sensitivity for detection of bacteria with FISH than with culture. Before FISH can be used for diagnostic purposes, the technique needs to be optimized to prevent false-negative results, for use on other patient materials and for detection of bacterial strains relevant for the orthopedic field like Propionibacterium acnes. In conclusion, FISH holds promise to be used as a diagnostic tool for identifying orthopedic infections